Assessment of Respondent Driven Sampling for Recruiting Female Sex Workers in Two Vietnamese Cities : Reaching the Unseen Sex Worker Respondent driven sampling -LRB- RDS -RRB- is a relatively new method to sample hard-to-reach populations . Until this study , female sex workers -LRB- FSWs -RRB- in Vietnam were sampled using a variety of methods , including time location sampling -LRB- TLS -RRB- , which may not access the more hidden types of FSWs . This paper presents an analysis from an HIV biological and behavioral surveillance survey to assess the feasibility and effectiveness of RDS to sample FSWs , to determine if RDS can reach otherwise inaccessible FSWs in Vietnam and to compare RDS findings of HIV risk factors with a theoretical TLS . Through face-to-face interviews with FSWs in Ho Chi Minh City -LRB- HCMC -RRB- and Hai Phong -LRB- HP -RRB- , data were collected about the venues where they most often solicit their clients . These data were used to create three variables to assess whether FSWs solicit their clients in locations that are visible , semi-visible and non-visible . For this analysis , the visible group simulates a sample captured using TLS . Survey results in HIV prevalence and related risk factors and service utilization , adjusted for sampling methodology , were compared across each of the three FSW visibility groups to assess potential bias in TLS relative to RDS . The number of self-reported visible FSWs -LRB- HCMC : n = 311 ; HP : n = 162 -RRB- was much larger than those of the semi-visible -LRB- HCMC : n = 65 ; HP : n = 43 -RRB- and non-visible -LRB- HCMC : n = 37 ; HP : n = 10 -RRB- FSWs in HCMC and HP . Non-visible FSWs in both cities were just as likely as visible and semi-visible FSWs to be HIV positive -LRB- HCMC : visible 14.5 % , semi-visible 13.8 % , non-visible 13.5 % , p value = 0.982 ; HP : visible 35.2 % , semi-visible 30.2 % , non-visible 30.0 % , p value = 0.801 -RRB- , to practice behaviors that put them at risk for contracting and transmitting HIV -LRB- injecting drug use -- HCMC : visible 13.8 % , semi-visible 12.3 % , non-visible 5.4 % , p value = 0.347 ; HP : visible 38.9 % , semi-visible 23.3 % , non-visible 30.0 % , p value = 0.378 , to have no condom use in the past month -- HCMC only : visible 52.7 % , semi-visible 63.1 % , non-visible 48.6 % , p value = 0.249 -RRB- and to have symptoms of a sexually transmitted infection -LRB- STI -RRB- in the past year -LRB- HCMC : visible 16.1 % , semi-visible 12.3 % , non-visible 16.2 % , p value = 0.742 ; HP : visible 13.6 % , semi-visible 18.6 % , non-visible 20.0 % , p value = 0.640 -RRB- . There was a difference found among the visible , semi-visible and non-visible groups in HP for no past month condom use -LRB- visible 53.1 % , semi-visible 79.1 % , non-visible 60.0 % , p value = 0.009 -RRB- . This study found that RDS was successful at recruiting hidden types of FSWs in Vietnam . Past reports of FSWs in Vietnam have assessed the more visible FSWs as being the most vulnerable and at risk for HIV . Although the number of visible FSWs is much higher than those of the semi and non-visible groups , this study found that the non-visible FSWs are very vulnerable to HIV infection . If prevention programs are targeting and responding to those who are most likely to be assessed -LRB- e.g. , more visible types of FSWs -RRB- then this analysis indicates that a significant proportion of the FSW population at risk for HIV may not be receiving optimal HIV information and services . Introduction and Background Vietnam is in the midst of an HIV epidemic concentrated among injection drug users -LRB- IDUs -RRB- and , increasingly , female sex workers -LRB- FSWs -RRB- . In recent years , the epidemic in Vietnam appears to be moving rapidly from IDU populations to FSWs through sexual contact with injecting male clients and the adoption of injection drug use behaviors by FSWs . Sexual transmission of HIV from FSWs to their non-injecting clients , who in turn have non-commercial sex partners , greatly increases the probability that HIV will spread to the general population . In 2002 , the Department of Social Evils in the Ministry of Labor , Invalids , and Social Affairs estimated that 130,000 women work as sex workers in Vietnam -LRB- other estimates put the number much higher -RRB- .1 -- 3 To understand and respond to HIV transmission patterns in Vietnam , numerous surveys have measured HIV prevalence and related risk factors among FSWs . However , the lack of sampling frames , relative rarity of this population , and their stigmatized and/or illegal behaviors , hinder investigators from obtaining representative samples of FSWs . Further , it is important to recognize the heterogeneity of the sex worker population . Broadly , FSW can be dichotomized into direct and indirect sex workers . Indirect sex workers typically have a primary job or source of income other than sex work , though that job may lead to contacts with potential clients -LRB- e.g. , bar maids or masseuses -RRB- . Direct sex workers typically do not have another job . Direct sex workers can be further broken down into street-based , brothel-based , or gatekeeper-based . The latter may involve a formal `` pimp '' / agent relationship or informal referrals from hotel concierges or taxi drivers . Use of the Internet to find clients is increasing also . There is a concerted effort by the Government of Vietnam to reduce prostitution by placing FSWs in administrative detention in government rehabilitation centers where they can spend anywhere from 1 month to several years . Fear of detention leads FSWs to exercise greater caution and more subtlety on the streets . Recently , FSWs have become even more difficult to reach because the Vietnamese government is imposing penalties -LRB- fines , jail sentences and possible closure -RRB- on the owners of entertainment establishments where sex is allegedly sold .4 As a result , FSWs will now wait off-site for an establishment owner or some other gatekeeper to contact them at a client 's request . FSWs are also hard to reach because they are highly mobile and move regularly from bar to bar , between districts and towns , and within and to other provinces .5 -- 9 Some FSWs are difficult to locate because they have primary jobs and engage in sex work part-time . For instance , women from rural areas may travel to urban areas to sell agricultural goods and only sell sex as a way to earn extra income .5 Higher paid FSWs , such as those who solicit clients from scooters , the Internet , through agents and over the telephone , have the financial capacity to remain hidden .5,10 Past efforts to survey FSWs in Vietnam , including annual sentinel HIV surveillance , have relied on convenience samples from rehabilitation centers and street-based FSWs . These samples comprise the type of FSWs who are reportedly the most vulnerable , and therefore most at risk , and visible , -LRB- i.e. , visible enough to be captured by the police or found by public health staff -RRB- and do not represent the entire sex work community .5 Further efforts to assess HIV related risk factors among FSWs have used other non-probability sampling methods , such as institutional sampling , targeted and chain referral sampling .11 -- 16 FSWs in Vietnam have also been sampled using a probability sampling method called time location sampling -LRB- TLS -RRB- , also known as time -- space or venue -- day -- time sampling .17,18 However , TLS can only be representative of those FSWs who are easily located at visible sites , thereby missing potentially important information from other types of FSWs . The Vietnamese Ministry of Health , with technical assistance from Centers for Disease Control and Prevention -- Global AIDS Program , conducted a survey using a relatively new sampling method to assess HIV prevalence , risk factors and service utilization among FSWs . The goal of the survey was to provide baseline information before increasing numbers of HIV prevention programs targeting these populations were initiated . This sampling method , known as respondent driven sampling -LRB- RDS -RRB- , is a variant of chain-referral sampling that utilizes an incentive for being interviewed and another incentive for recruiting peers -LRB- other FSWs -RRB- to be interviewed .19 -- 22 Sampling begins by selecting a small number of non-randomly selected members of the target population , known as seeds , to take part in the study . Seeds initiate the chain referral by recruiting a fixed number of peers who , in turn , recruit other peers . The process continues until the target sample size is attained . Links among peers are recorded using anonymous identification numbers . Although RDS is relatively new to public health researchers , it is starting to be used widely in place of other well known types of sampling methods for hard to reach populations . Researchers are considering the advantages of using RDS in place of TLS , the only other probability method for hard to reach populations , to conduct future HIV biological and behavioral surveillance surveys . TLS has been used to sample FSWs who gather and are accessible at public locations -LRB- or venues -RRB- that can be listed in a sampling frame .23 -- 25 TLS entails identifying days and times when the target population gathers at specific locations -LRB- e.g. , brothels , city blocks , bars -RRB- , constructing a sampling frame of time and location units , randomly selecting these units and systematically intercepting consenting members of the target population for interviews .24 -- 26 When implemented correctly , TLS allows researchers to construct a sample with known probabilities , make statistical inferences to the larger population of venue visitors , and theorize about the introduction of biases that may limit generalization of results to the target population .23 Two TLS surveys of FSWs in Vietnam have been reported . In 2000 Family Health International -LRB- FHI -RRB- conducted a behavioral survey with karaoke -LRB- n = 2,302 -RRB- and street-based -LRB- n = 1,300 -RRB- FSWs in five Vietnamese cities using TLS .18 During 2003 , the Vietnamese National Institute of Hygiene and Epidemiology collected data from karaoke -LRB- n = 1,367 -RRB- and street-based -LRB- n = 976 -RRB- FSWs from five provinces .17 Although TLS can produce a probability sample by ensuring that time -- location units are enumerated and selected randomly , it allows researchers to reach only those segments of the population who are visible and identifiable . Depending on the population of interest , this may introduce a bias by differential sampling of the portion of the population which is most at-risk . TLS can be expected to miss those segments that are less visible -LRB- e.g. , FSWs who solicit clients through agents , by telephone or Internet -RRB- . The `` visible '' portion of a population does not represent the whole population any more than an institution or clinic-based population does ; `` hidden '' population members have a zero probability of selection , reducing representativeness of the sample . The objectives of this paper are to present findings from a survey on HIV prevalence , risk behaviors and service utilization to -LRB- 1 -RRB- assess the effectiveness of RDS to sample FSWs in Vietnam ; and -LRB- 2 -RRB- to compare RDS findings with theoretical TLS . This is especially important given that evaluations of RDS used for HIV surveillance have only come from IDUs and males who have sex with males populations in the United States .20,22,27 -- 29 Until this study , RDS has not been evaluated in Asia among FSWs . This methodology warrants investigation to assess its ability to sample hard to reach populations in international settings . Materials and Methods Data to evaluate RDS were collected from FSWs in Ho Chi Minh City -LRB- HCMC -RRB- and Hai Phong -LRB- HP -RRB- , Vietnam . Eligible participants were over the age of 18 and had exchanged sex for money in the previous month . FSWs were recruited by their peers -LRB- other FSWs -RRB- and provided a small monetary incentive for completing a questionnaire and providing a saliva sample to test for HIV -LRB- US \ $ 3 in HP and US \ $ 4 in HCMC -RRB- . FSWs were provided another incentive for recruiting up to three other FSWs to participate -LRB- approximately US \ $ 1 in HP and US \ $ 1.50 in HCMC for each eligible recruit -RRB- . Data were gathered from FSWs in HP from April to June and in HCMC from May to July , 2004 . Recruitment began with 20 FSWs , non-randomly selected by survey staff , in each city . Outreach workers selected these initial recruits , or `` seeds , '' based on where they most often solicited their clients . A majority of the seeds were from the visible groups , street-based and karaoke-based FSWs . A few seeds from hotels and guesthouses were recruited . Once seeds consented , they completed a one-hour face-to-face interview with a trained Vietnamese interviewer . The interview instrument consisted of questions about the participant 's demographic background , current and past drug use , sexual behaviors , HIV knowledge , risk perceptions and service utilization , and about where they usually solicit their clients . After the interview , survey staff provided participants with three coupons with which to recruit up to three other FSWs who were co-workers , friends , acquaintances or family members . Each coupon contained a unique identification number and provided basic information about the study and the addresses of the interview sites . Respondent/recruiters were asked to return to collect their incentives for successful recruits . A brief follow-up questionnaire was administered during this visit to ascertain the recruiter 's relationship to their recruits and the number and type of refusals they received . This permitted the assessment of participation bias due to refusals or no-shows . Oraquick ™ HIV antibody rapid test kits for oral fluids were used for HIV testing . No one refused to provide an oral sample . Participants did not learn their test results at the interview site but were provided a voucher to receive a free HIV test with counseling at a nearby voluntary counseling and testing -LRB- VCT -RRB- center . For the assessment of bias in a theoretical TLS-drawn sample in comparison to an actual RDS-drawn sample , respondents were classified as accessible , i.e. , visible to TLS , if they reached their clients in a public venue . Categories were established from the response to the question , `` Where do you usually reach your clients ? '' Responses were aggregated into three groups : visible -LRB- street , park , karaoke bar -RRB- ; semi-visible -LRB- brothel , guesthouse , hotel -RRB- ; non-visible -LRB- agent , telephone , Internet -RRB- . Our assumption is that the visible group could potentially be captured by TLS . The semi visible group may or may not be captured with TLS , and the non-visible group would be missed with TLS .1 Statistical Analysis Adjusted proportions and 95 % confidence intervals -LRB- ci -RRB- for FSWs ' level of visibility were analyzed using the RDS analysis tool -LRB- RDSAT -RRB- .30 RDSAT adjusts proportion estimates for participants ' network sizes and recruitment patterns .20,31 RDSAT adjustments use principles of social network theory to account for biases found in conventional chain referral sampling .31,32 Chi-square proportions and p-values for comparisons of HIV risk factors and service utilization of RDS and theoretical TLS were analyzed using SPSS 11.0 . Five of the 20 non-randomly selected seeds in the HP sample , and four seeds in the HCMC sample were not used in the final analysis since they did not recruit any peers . It is not known why these seeds did not recruit anyone . The sample size was calculated based on 15 % increase in use and knowledge of CDC sponsored VCT HIV services and outreach . We estimated low baseline knowledge and use of services -LRB- no actual data available -RRB- with high HIV prevalence . HP sample size was 200 based on higher knowledge from existing health education programs . The sample size in HCMC was 400 , assuming lower baseline knowledge . Design effect was set at 2 . This study was reviewed by the Associated Director for Science of the National Center for HIV , STD and TB prevention at CDC who classified this as a surveillance activity . The protocol for this study was reviewed and approved by the LIFE-GAP Office of the Vietnam Ministry of Health . Findings A total of 628 individuals , including seeds , were interviewed in fixed interview sites in HCMC -LRB- n = 413 -RRB- and HP -LRB- n = 215 -RRB- . The majority of the FSWs in the HCMC -LRB- 54.6 % -RRB- and HP -LRB- 51.3 % -RRB- sample were under the age of 29 years old . More than 50 % of FSWs in HCMC and HP had no occupation other than selling sex . During the follow-up visits to collect recruitment incentives , most participants reported giving out all of their coupons . According to the 174 recruiting participants in HCMC and 90 in HP , each of whom received three coupons , a total of 75 -LRB- 15.3 % -RRB- individuals in HCMC and 24 -LRB- 10 % -RRB- in HP refused to accept a coupon ; 147 recruiters in HCMC and 83 in HP reported that they were successful in distributing their coupons and that no one to whom they tried to give a coupon rejected one ; so refusals were clustered among a handful of recruiters , 27 in HCMC and 7 in HP . According to recruiters , most refusers did so because of `` fear of identification , '' -LRB- 57 % in HCMC ; 75 % in HP -RRB- , others `` felt uncomfortable '' -LRB- 27 % in HCMC ; 8.3 % in HP -RRB- , still others thought they were `` too busy '' -LRB- 10.7 % in HCMC -RRB- , others thought the `` incentive not worth the time '' -LRB- 17 % HP -RRB- and a small number of FSWs in HCMC responded that they were `` not interested . '' Overall , the recruited FSWs were diverse with respect to where they solicited their clients . Figure 1 depicts the diversity of sex work types among the links within a single recruitment chain of FSWs in HCMC -LRB- n = 59 recruits -RRB- . In this example , the seed recruited three FSWs who were not street-based : two based in guesthouses and one based in karaoke .2 The selected karaoke-based FSW recruited two other karaoke-based and one guesthouse-based FSW . Near the outer waves of this recruitment chain , there are some more hidden types of FSWs such as agent-based and telephone-based FSWs . Figure 1RDS recruitment network for one seed for type of female sex worker in HCMC , Vietnam . The distribution by visibility was visible -LRB- HCMC , n = 311 ; HP , n = 161 -RRB- , semi-visible -LRB- HCMC , n = 65 ; HP , n = 43 -RRB- and non-visible -LRB- HCMC , n = 37 ; HP , n = 12 -RRB- . Figure 2 shows that the largest adjusted proportions of FSWs in both HCMC and HP reached by RDS were visible -LSB- HCMC , 73.7 % ; 95 % ci -LRB- 67.0 % , 79.5 % -RRB- and HP , 75.9 % ; ci -LRB- 67.1 % , 85.3 % -RRB- -RSB- . RDS reached a small proportion of non-visible -LSB- HCMC , 9.3 % ; ci -LRB- 6.0 % , 13.1 % -RRB- and HP , 9.7 % ; ci -LRB- 1.3 % , 18.2 % -RRB- -RSB- and semi-visible FSWs -LSB- HCMC , 16.9 % ; ci -LRB- 11.5 % , 23.4 % -RRB- and HP , 14.2 % ; ci -LRB- 9.1 % , 21.2 % -RRB- -RSB- , who theoretically could have been missed by TLS . Figure 2Distribution of visible , semi-visible and non-visible FSWs in HCMC and Hai Phong , Vietnam ; adjusted proportions -LRB- number -RRB- . Visible FSWs are assessed to be the most visible of the FSWs in Vietnam ; semi-visible FSWs are assessed as not always being easily identifiable ; and non-visible FSWs are assessed as the most hidden types of FSWs in Vietnam . HIV Risk Factors There were minor differences among FSW visibility groups with regard to HIV status and related risk behaviors -LRB- see Table 1 -RRB- . Table 1HIV prevalence , risk factors and drug use among visible , semi-visible and non-visible FSWs in Ho Chi Minh City and Hai Phong ; unadjusted proportions -LRB- number -RRB- , p-value Ho Chi Minh City -LRB- n = 413 -RRB- Hai Phong -LRB- n = 215 -RRB- Visible % -LRB- n -RRB- Semi-visible % -LRB- n -RRB- Non-visible % -LRB- n -RRB- p-valueVisible % -LRB- n -RRB- Semi-visible % -LRB- n -RRB- Non-visible % -LRB- n -RRB- p-valueHIV positive status14 .5 -LRB- 45 -RRB- 13.8 -LRB- 9 -RRB- 13.5 -LRB- 5 -RRB- 0.98235.2 -LRB- 57 -RRB- 30.2 -LRB- 13 -RRB- 30.0 -LRB- 3 -RRB- 0.801 No condom use with a partner in the past month52 .7 -LRB- 164 -RRB- 63.1 -LRB- 41 -RRB- 48.6 -LRB- 18 -RRB- 0.24953.1 -LRB- 86 -RRB- 79.1 -LRB- 34 -RRB- 60.0 -LRB- 6 -RRB- 0.009 Ever used non-injection illicit drugs20 .9 -LRB- 65 -RRB- 18.5 -LRB- 12 -RRB- 29.7 -LRB- 11 -RRB- 0.38546.9 -LRB- 76 -RRB- 37.2 -LRB- 16 -RRB- 60.0 -LRB- 6 -RRB- 0.338 Ever injected illicit drugs13 .8 -LRB- 43 -RRB- 12.3 -LRB- 8 -RRB- 5.4 -LRB- 2 -RRB- 0.34738.9 -LRB- 63 -RRB- 23.3 -LRB- 10 -RRB- 30.0 -LRB- 3 -RRB- 0.378 Symptoms of a sexually transmitted infection in past year16 .1 -LRB- 50 -RRB- 12.3 -LRB- 8 -RRB- 16.2 -LRB- 6 -RRB- 0.74213.6 -LRB- 22 -RRB- 18.6 -LRB- 8 -RRB- 20.0 -LRB- 2 -RRB- 0.640 HIV positive test status did not differ by visibility group in HCMC or HP . In HCMC and HP , a higher proportion of visible FSWs tested positive for HIV -LRB- 14.5 and 35.2 % , respectively -RRB- than semi-visible -LRB- 13.8 % , 30.2 % -RRB- and non-visible -LRB- 13.5 and 30.0 % -RRB- FSWs . The only significant difference among the groups for any variable was in HP , for `` no past month condom use with a partner '' -LRB- p value = 0.009 -RRB- . Visibility groups in both HCMC and HP did not differ with respect to reported use of non-injection illicit drugs ever and injected illicit drugs ever or reporting a sexually transmitted infection -LRB- STI -RRB- during the previous year . Service Utilization Contact with a peer educator -LRB- PE -RRB- , source of HIV information and HIV testing did not vary significantly by visibility group in either city . Among all three visibility groups in both cities , fewer than 50 % had ever made contact with a PE . More than 50 % of FSWs in both cities -LRB- with the exception of semi-visible FSWs in HP -RRB- reported receiving their HIV information from television , radio , newspapers or magazines . More HCMC FSWs reported receiving HIV information from friends than from health workers and PEs ; this pattern was reversed for HP FSWs -LRB- Table 2 -RRB- . Table 2HIV service utilization among visible , semi-visible and non-visible FSWs in Ho Chi Minh City and Hai Phong ; unadjusted proportions -LRB- number -RRB- , p-value Ho Chi Minh City -LRB- n = 413 -RRB- Hai Phong -LRB- n = 215 -RRB- Visible % -LRB- n -RRB- Semi-visible % -LRB- n -RRB- Non-visible % -LRB- n -RRB- p-valueVisible % -LRB- n -RRB- Semi-visible % -LRB- n -RRB- Non-visible % -LRB- n -RRB- p-valueEver met with a peer educator33 .8 -LRB- 105 -RRB- 49.2 -LRB- 32 -RRB- 40.5 -LRB- 15 -RRB- 0.31031.5 -LRB- 51 -RRB- 27.9 -LRB- 12 -RRB- 40.0 -LRB- 4 -RRB- 0.720 Most common source of HIV information0 .0880.106 TV , radio , newspaper or magazine56 .1 -LRB- 171 -RRB- 70.8 -LRB- 46 -RRB- 52.9 -LRB- 18 -RRB- 57.5 -LRB- 92 -RRB- 45.2 -LRB- 19 -RRB- 70.0 -LRB- 7 -RRB- Health worker/peer educator17 .0 -LRB- 52 -RRB- 9.2 -LRB- 6 -RRB- 20.6 -LRB- 7 -RRB- 26.3 -LRB- 42 -RRB- 38.1 -LRB- 16 -RRB- 30.0 -LRB- 3 -RRB- Friends20 .7 -LRB- 63 -RRB- 13.8 -LRB- 9 -RRB- 26.5 -LRB- 9 -RRB- 11.3 -LRB- 18 -RRB- 16.7 -LRB- 7 -RRB- 0 Other6 .2 -LRB- 19 -RRB- 6.2 -LRB- 4 -RRB- 05.0 -LRB- 8 -RRB- 00Ever had an HIV test45 .3 -LRB- 141 -RRB- 46.2 -LRB- 30 -RRB- 40.5 -LRB- 15 -RRB- 0.84134.0 -LRB- 55 -RRB- 27.9 -LRB- 12 -RRB- 50.0 -LRB- 5 -RRB- 0.398 Type of facility providing last HIV test0 .9760.285 Public clinic35 .6 -LRB- 51 -RRB- 43.4 -LRB- 13 -RRB- 33.3 -LRB- 5 -RRB- 46.3 -LRB- 25 -RRB- 16.7 -LRB- 2 -RRB- 40.0 -LRB- 2 -RRB- Hospital43 .7 -LRB- 62 -RRB- 36.7 -LRB- 11 -RRB- 33.3 -LRB- 5 -RRB- 29.6 -LRB- 16 -RRB- 25.0 -LRB- 3 -RRB- 40.0 -LRB- 2 -RRB- Private clinic4 .2 -LRB- 6 -RRB- 3.3 -LRB- 1 -RRB- 6.7 -LRB- 1 -RRB- 1.9 -LRB- 2 -RRB- 16.7 -LRB- 2 -RRB- 0 VCT center6 .3 -LRB- 9 -RRB- 6.7 -LRB- 2 -RRB- 13.3 -LRB- 2 -RRB- 9.3 -LRB- 5 -RRB- 16.7 -LRB- 2 -RRB- 2.0 -LRB- 2 -RRB- Rehab center9 .9 -LRB- 14 -RRB- 10.0 -LRB- 3 -RRB- 13.3 -LRB- 2 -RRB- 13.0 -LRB- 7 -RRB- 25.0 -LRB- 3 -RRB- 0 Fifty percent or fewer FSWs in each visibility group reported ever having an HIV test . Among those HCMC and HP FSWs who ever had an HIV test , the majority received their test at either a public clinic -LRB- district or community public health center or STI clinic -RRB- or hospital , with the exception of HP semi-visible FSWs who reported receiving their HIV test from either a hospital or a drug user/sex worker rehabilitation center . Twice as many non-visible -LRB- 13.3 % -RRB- , in comparison to visible and semi-visible -LRB- 6.3 % each -RRB- FSWs in HCMC , reported receiving their HIV test at a VCT center . Discussion The analysis of RDS coverage demonstrates that this method may provide modestly better estimates for FSW populations than TLS because it reaches individuals ostensibly inaccessible by TLS . The level of risk and HIV prevalence in the less visible groups of FSWs was similar to the semi-visible and visible FSWs . This would indicate that less visible FSWs merit reasonable efforts to assure that these groups are targeted within all interventions for FSWs . The differences might have differed if two groups emerged rather than three . However , the semi-visible group could not be clearly dichotomized . The three visibility groups in HCMC and HP did not differ significantly , which may contradict previous reports that higher paid , indirect FSWs , in general , have less HIV risk than direct FSWs .5,11,33 High proportions of respondents among all visibility groups in HCMC and HP reported inconsistent condom use with a sexual partner in the past month , possibly indicating that all three groups of FSWs are not being appropriately educated about using condoms or that they can not easily access them . Other possible barriers to increased condom use might include poor negotiating skills with their clients or a false perception that a well-dressed client with an occupation may not be HIV-infected . Understanding the perceptions , negotiation skills and the reasons why some FSWs use condoms and others do not is essential to addressing the low proportion of condom use among FSWs in these cities . The high proportion of non-visible FSWs in HCMC and HP who ever met with a PE indicates that the more hidden FSWs may be receiving more exposure to HIV information than previously believed . HCMC and HP FSWs reported similar sources for HIV information , indicating that PEs may be equally disseminated among the visibility groups . Furthermore the high proportion of non-visible FSWs who ever had an HIV test and their access to HIV testing at public clinics , hospitals and VCT centers indicate that this group has some awareness of and interest in their risk . It would be useful to gather qualitative data to determine how they obtained information and services . Another key finding was the nature of social networks formed by FSWs in Vietnam . Networks were dense and diverse enough to provide a large sample in a short time that crossed the various types , direct and indirect , of FSWs working in the respective cities . These network properties are essential to the successful use of RDS . RDS had an added advantage over TLS by providing some measure of selection bias by questioning respondents on the characteristics of peers who demurred . TLS can not determine reasons for not using a venue to solicit clients , only for respondents ' refusal to speak with interviewers . There were limitations to our study . Categories of visibility were based on the authors ' perceptions of the sex work industry in the respective cities . We did not conduct extensive fieldwork so there was limited knowledge about the types of FSWs in Vietnam . There was too little formal research about characteristics of hotel and guesthouse-based FSWs to confidently dichotomize them as visible or non-visible . With a better understanding of these types of FSWs , reclassification and reanalysis of the data could better demonstrate the capacity of RDS to reach hidden FSWs . Furthermore , the question `` Where do you usually reach your clients ? '' does not signify where a FSW always reaches her clients . The findings here may have non-differentially misclassified some respondents . Currently RDS data analysis is limited to estimates of proportions . Stratified analysis of the differences in risk factors among visibility groups might yield more information when RDSAT is updated . The best scenario for testing whether RDS captures more hidden elements of the FSW population would be to conduct nearly contemporaneous surveys using TLS and RDS in the same population . Using RDS data to simulate TLS for comparisons of the two sampling methods is subject to any biases unique to RDS that might not be found in TLS . Although non-visible FSWs make up a small proportion of the FSW sample in HCMC , their high HIV prevalence and associated risk factors is alarming , especially when past efforts to sample FSWs , using TLS and convenience sampling , and sentinel surveillance in STI clinics , are likely to have missed these groups . Missing the most inaccessible portions of the FSW population could result in a biased understanding of HIV sero-prevalence and risk factors and , consequently , could lead to inefficient planning for HIV prevention and intervention programs for the entire FSW population . Recurrent round-ups of FSWs drive FSWs off the street , making them increasingly difficult to find in public venues . If current prevention programs are targeting and responding to those who are most likely to be assessed -LRB- more visible FSWs -RRB- then it is possible that an important segment of the FSW population at risk for HIV is not receiving optimal HIV information and services . However , this study found that segments were accessing services at about the same low rates , indicating a need to increase service utilization among all groups of FSWs . Based on these findings , we recommend using RDS for future surveys of FSWs in Vietnam to prevent the omission of the less accessible members of this population .

O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O B O O O O O O O B O O O O O O B O O O O O O O O O O O O O O B I O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O B O O O O O O O O O O O O O O O O O B O O O B O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O B O B O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O


Quality of Water the Slum Dwellers Use : The Case of a Kenyan Slum As a result of rapid urbanization in a context of economic constraints , the majority of urban residents in sub-Saharan Africa live in slums often characterized by a lack of basic services such as water and sewerage . Consequently , the urban poor often use inexpensive pit latrines and at the same time may draw domestic water from nearby wells . Overcrowding in slums limits the adequate distance between wells and pit latrines so that micro-organisms migrate from latrines to water sources . Sanitary practices in these overcrowded slums are also poor , leading to contamination of these wells . This study sought to assess sanitary practices of residents of a Kenyan urban slum and fecal contamination of their domestic water sources . This cross-sectional study involved 192 respondents from Langas slum , Kenya . Forty water samples were collected from the water sources used by the respondents for laboratory analysis of coliforms . Of these 40 samples , 31 were from shallow wells , four from deep wells , and five from taps . Multiple-tube fermentation technique was used to enumerate coliform bacteria in water . The study found that most people -LRB- 91 % -RRB- in the Langas slum used wells as the main source of domestic water , whereas the rest used tap water . Whereas most people used pit latrines for excreta disposal , a substantial percentage -LRB- 30 % -RRB- of children excreted in the open field . The estimated distance between the pit latrines and the wells was generally short with about 40 % of the pit latrines being less than 15 m from the wells . The main domestic water sources were found to be highly contaminated with fecal matter . Total coliforms were found in 100 % of water samples from shallow wells , while 97 % of these samples from shallow wells were positive for thermotolerant coliforms . Three out of the four samples from deep wells were positive for total coliforms , while two of the four samples were positive for thermotolerant coliforms . None of the samples from taps were positive for either total or thermotolerant coliforms . Because the presence of thermotolerant coliforms in water indicates fecal contamination , facilitated by the proximity between the wells and pit latrines , the study suggests that the pit latrines were a major source of contamination of the wells with fecal matter . However , contamination through surface runoff during rains is also plausible as indiscriminate excreta disposal particularly by children was also common . Owing to the fecal contamination , there is a high possibility of the presence of disease pathogens in the water ; thus , the water from the wells in Langas may not be suitable for human consumption . To address this problem , treatment of the water at community or household level and intensive behavioral change in sanitary practices are recommended . Efforts should be made to provide regulated tap water to this community and to other slums in sub-Saharan Africa where tap water is not accessible . However , more sampling of different water sources is recommended . INTRODUCTION Rapid urban growth in a climate of economic constraints has resulted in the majority of residents in Africa 's large cities , and an increasing proportion of Africans overall , living in overcrowded slums and shantytowns . In these slums and shantytowns , health conditions and livelihood opportunities are poor .1 -- 3 Available evidence indicates that the poor urban residents of Africa exhibit higher morbidity , have poor access to health services , and consequently exhibit higher mortality rates than residents of other areas including rural residents .4 -- 8 The situation in Kenya is similar to other situations in Africa . The proportion of urban population in Kenya nearly doubled between 1980 and 1998 , increasing from 16 to 31 % .9 Rapid urbanization amid economic degradation in Kenya has resulted in an increased proportion of people living in absolute poverty in the urban areas .10 Therefore , poverty has increasingly become a crucial urban problem in Kenya leading to mushrooming of informal settlements in the urban parts of Kenya where the urban poor find shelter . This has overwhelmed the environmental health resources in urban areas . Because of their illegal status , residents of informal settlements in Kenya do not receive government services such as water , drainage , sewerage , and rubbish collection . Consequently , informal settlements are characterized by poor environmental conditions that predispose their inhabitants to poor health outcomes .4 Evidence shows that children of poor families in urban areas of Kenya exhibit poorer health conditions than their rural counterparts . According to a report by African Population and Health Research Center -LRB- APHRC -RRB- in 2002,4 infant and child mortality risks are particularly higher in the slums of Nairobi than those observed in other urban areas and in rural Kenya . For instance , the under five mortality was 35 % higher among slum residents in Nairobi than among the rural population in Kenya . The report attributes these patterns to poor water and sanitation in these slum settlements .4 An adequate supply of safe drinking water is universally recognized as a basic human need . Yet millions of people in the developing world do not have ready access to an adequate and safe water supply . By 1996 , the number of people without access to safe water in urban areas was rising sharply in developing countries as a result of rapid urbanization , much of which was occurring in peri-urban and slum areas .11 Because the United Nations projects a rapid population growth in urban areas between 2000 and 2030,12 access to safe drinking water and adequate sanitation in urban areas is likely to worsen unless there is a drastic policy change to cater to the needs of the urban poor . Human excreta and the lack of adequate personal and domestic hygiene have been implicated in the spread of many infectious diseases including cholera , typhoid , hepatitis , polio , cryptosporidiosis , ascariasis , and schistosomiasis . It is estimated that one-third of deaths in developing countries are caused by the consumption of contaminated water and on average as much as one-tenth of each person 's productive time is sacrificed to water-related diseases .13 The World Health Organization estimates that 2.2 million people die annually from diarrhea diseases and that 10 % of the population of the developing world are severely infected with intestinal worms related to improper waste and excreta management .14,15 In Kenya , diarrheal diseases are among the major illnesses affecting children of the slum residents . According to the report by APHRC in 2002 , prevalence of diarrhea was 32 % among children below 5 years of age in the slums , which is double the rate for Nairobi and the national average .4 Where ground water is used as a source of domestic water , use of pit latrines is not recommended because the two are incompatible unless the water table is extremely low and soil characteristics are not likely to contribute to contamination of ground water . Where they coexist , although it is difficult to give a general rule for all soil conditions , the commonly used guideline is that the well should be located in an area higher than and at least 15 m from the pit latrines and should be at least 2 m above the water table . Available evidence shows that increased lateral separation between the source of pollution and groundwater supply reduces the risk of fecal pollution .16 Coexistence of on-site sanitation and use of underground water has in the past been mainly confined to the rural areas where there is adequate land to allow for adequate distance between pit latrines and shallow wells . With the rapid urbanization and rapid expansion of slum settlements in sub-Saharan Africa , on-site sanitation and underground water are used in some urban areas because they are affordable options in the absence of government-supplied services . However , the congestion in the urban slums does not allow for adequate distance between the wells and the pit latrines , which allows micro-organisms to migrate from fecal contents into the underground water sources . Furthermore , poor sanitary practices -LRB- for example , disposal of human excreta -RRB- in these slum areas lead to contamination of water and consequently water-borne diseases . It is in this context and in the context of high levels of diarrheal diseases in the urban slums in Kenya that this study sought to assess the sanitary practices and the fecal contamination of domestic water sources in an urban slum in Eldoret , Kenya . STUDY CONTEXT The study was conducted between January and June 1999 in Langas , an urban slum in Eldoret municipality , Kenya , less than 10 km from Eldoret town . Eldoret town is located in the Rift Valley Province , about 330 km north west of Nairobi . Eldoret , the headquarter of Uasin Gishu District , is one of the fastest growing urban areas in Kenya . Langas falls under high density , low-income areas of the Eldoret municipality . It is divided into four administrative blocks that are further subdivided into about 2,500 plots . Each plot -LRB- 1/8 of an acre -RRB- has between one and 30 households each with an average of six occupants . Settlement in Langas began in 1965 and at the time there were no basic services . Early settlers dug shallow wells for their water needs .17 The water table is high , and this raises the possibility of ground water contamination where on-site sanitation systems are in use . METHODOLOGY A cross-sectional study design was used and a sample of 192 households1 was selected through multistage sampling technique as follows : two out of the four administrative blocks were randomly picked and from the two blocks , 192 plots were picked . From each of the selected plots , one household was selected to participate . The 192 households were selected as follows : starting from one corner of each of the blocks and walking across the two blocks in a more or less a diagonal line , about every plot on the diagonal line was selected until the sample of 192 was reached . From each of these plots , one household was selected to represent the plot -LRB- this depended mainly on availability of respondents and their willingness to participate -RRB- , and the first household to be contacted in a selected plot was considered for recruitment into the sample . From the household , a credible respondent was interviewed . A credible respondent was a resident of the selected household who was aged 18 years or above . For water sampling , 20 samples were taken from water points in each of the two blocks to make a total of 40 samples . This number for water samples was determined by financial and logistical feasibility . In most circumstances , residents of a plot shared one water source and there was roughly one water point per plot . In a few cases , several plots shared a water point . To get the 40 samples , every fourth household2 of the 192 households included in the interview sample was asked their source of water and a water sample was taken from this source so long as it had not already been taken . In the event that a previous fourth household shared the source with the current household , the source for the immediate next household in the study sample was considered . Of the 40 water samples , 31 were from shallow wells -LRB- defined as a hand-dug well -RRB- , four from deep wells -LRB- defined as a drilled well -RRB- and five from taps -LRB- referring to tap water from the municipal council distribution system -RRB- . Using the above described criteria , only one deep well was selected and purposive sampling was then used to get three other such wells , consequently including all the deep wells that were used by the study sample . Questionnaires were administered to the 192 selected households to obtain information on the type of toilet facility used , major source of domestic water , method of human waste disposal , whether drinking water was boiled , and the perceptions of possible sources of water contamination in the area . For the method of excreta disposal and water source , the main method and source were considered in instances where there was more than one method or source , respectively . The distance between the pit latrines used by the 192 households and the wells -LRB- in cases where they used wells -RRB- was estimated . We also observed sanitation practices . Water samples were collected aseptically with sterile sampling bottles . The samples were transported within 2 hours of collection in a cool box containing ice packs to the Faculty of Health Sciences , Moi University microbiology laboratory for analysis . Fecal contamination of the water was determined through isolation of indicator organisms , total coliforms , and then thermotolerant -LRB- fecal -RRB- coliforms , through multiple-tube fermentation -LRB- MTF -RRB- technique . Probability tables -LRB- McCrady tables -RRB- were used to determine the Most Probable Number -LRB- MPN -RRB- estimates of the coliform organisms per 100 ml of water . Analysis of data was generally descriptive , involving determination of frequencies . Stata statistical package was used to analyze the data . RESULTS Method of Excreta Disposal The majority of respondents -LRB- 98 % -RRB- said that adults used pit latrines , whereas the rest said adults defecated indiscriminately . Similarly , a majority of respondents -LRB- 70 % -RRB- said that children used pit latrines , whereas 30 % said children used open field/defecated indiscriminately . Most of the pit latrines -LRB- 95 % -RRB- in the community were traditional , whereas the rest were ventilated improved pit latrines -LRB- VIP latrines -RRB- . A walk through the community confirmed the report that some people excreted indiscriminately as human excreta was observed strewn all over the compounds . Source of Domestic Water Most people -LRB- 89 % -RRB- said they used shallow wells as the major source of domestic water , whereas 2 % said they used water from deep wells and the rest said they used tap water from the municipal council -LRB- Table 1 -RRB- . The shallow wells often had no concrete slab and often the aperture was not covered at all or was poorly covered with a loose lid that was not lockable , whereas the deep wells had a piped system . Those who used deep wells were mainly the more affluent people in the community who often owned the plot in which the well was situated . Tap water was mainly from water kiosks where water was being sold to the slum residents . Respondents who did not use the tap water said that the water from water kiosks was expensive and unaffordable to be used for domestic purposes .3 Problems of unreliability were mentioned as hindering use of tap water from the kiosks as some respondents said that sometimes the kiosk near their house could remain closed for a whole day or more . Some of the respondents reported that the nearest water kiosk was too far from their homes . TABLE 1Source of domestic water among 192 sampled households in Langas Slum , KenyaSource of domestic waterNumberPercentTap178 .9 Shallow well17189 .1 Deep well42 .1 Total192100 Distance between Pit Latrine and Well The wells were very close to the pit latrines . In many circumstances -LRB- 38 % -RRB- , the distance between the wells and the pit latrines was estimated to be less than 15 m -LRB- the commonly used guideline is that the distance should be at least 15 m -RRB- . Most wells -LRB- about 59 % -RRB- were estimated to be at a distance between 15 and 30 m from the pit latrines -LRB- Table 2 -RRB- . The distance between pit latrines and wells for the wells from which water samples were taken was similar to that of other wells -LRB- Table 3 -RRB- . TABLE 2Distance between pit latrine and wells for all wells in the study in Langas Slum , KenyaDistanceNumberPercent1 -- 15 m6738 .315 -- 30 m10358 .930 m and above52 .9 Total175 * 100 * This total reflects only wells , and thus excludes taps.TABLE 3Distance between pit latrine and well for wells whose water was sampled in Langas Slum , KenyaDistanceNumberPercent1 -- 15 m144015 -- 30 m195430 m and above26Total35 * 100 * This total reflects only wells whose water was sampled , and thus excludes taps . Boiling of Drinking Water Despite the short distance estimated between the pit latrines and the wells and the poor sanitary practices like indiscriminate excreta disposal , only 42 % of those who reported using wells said they boiled their drinking water , when asked if they did . Residents ' Perception of Contamination Respondents pointed out various possible sources of contamination of the water sources in the area . These included children dipping dirty objects into water source -LRB- 34 % -RRB- as the main source of contamination , drawing water from the source with dirty containers -LRB- 27 % -RRB- , domestic animals defecating around water sources -LRB- 19 % -RRB- , and people washing clothes -LRB- 5 % -RRB- at the water source , among others . Interestingly , no one mentioned closeness of the well to the pit latrines as a possible source of contamination . Water Analysis Results Forty water samples were analyzed : 31 from shallow wells , four from deep wells , and five from taps . Wells Shallow Wells All the samples -LRB- 31 -RRB- taken from shallow wells were positive for total coliforms . The most probable number of total coliforms for most of the samples -LRB- 71 % -RRB- was 1,100 + per 100 ml . The minimum number of total coliforms was 63 , whereas the maximum was 1,100 + coliforms per 100 ml water . Only one of the samples had no thermotolerant coliforms at all , whereas most had 1,100 + thermotolerant coliforms per 100 ml . Deep -LRB- Drilled -RRB- Wells Of the four samples taken from the deep wells , three were positive for total coliforms , whereas one was negative . The highest number of total coliforms was 240 . For thermotolerant coliforms , two samples were negative . The maximum number of thermotolerant coliforms was 23 . Taps For the five samples taken from taps -LRB- municipal tap water -RRB- , all of them were negative for total coliforms and consequently thermotolerant coliforms . DISCUSSION This paper provides evidence on the extent of contamination of main domestic water sources in the Langas slum and suggests the most probable sources of this contamination . The evidence reveals that the most probable sources of contamination are hardly mentioned among the many sources perceived to contaminate the water sources by the residents of the slum , which impacts how interventions ought to be developed . The results indicate that the majority of the community members used pit latrines and at the same time used wells as the major source of domestic water . The conditions found in Langas do not fulfill the recommendations given for coexistence of onsite sanitation and use of ground water for domestic purposes , which indicate that there should be an adequate lateral separation between the pit latrine and the well to reduce chances of fecal contamination of the ground water .16 The distance between the wells and the pit latrines was estimated to be generally short with nearly 40 % of the pit latrines estimated to be at a distance of less than 15 m from the wells . This raises the risk of contamination of the water sources as coliforms migrate from the pit latrines to the wells . The presence of indicator organisms -LRB- Escherichia coli or thermotolerant coliform bacteria -RRB- in water indicates recent contamination of the water source with fecal matter and hence possible presence of intestinal pathogens . According to World Health Organization -LRB- WHO -RRB- guidelines , E. coli or thermotolerant coliform bacteria should not be detectable in any water intended for drinking .18 The laboratory analysis results of water samples in this study show that fecal matter heavily contaminated the water sources and especially the shallow wells . None of the shallow wells met the WHO requirements for water intended for drinking . The presence of indicator organisms in the water samples collected from the wells indicates the coliforms migrated from fecal matter in the pit latrines through the soil to the water sources , facilitated by the very short distance between the pit latrines and the wells . Poor sanitary practices are also likely sources of pollution of the water sources . Sanitary practices were found to be generally poor from observation and from responses from the respondents . Thirty percent of children excreted indiscriminately and consequently there were a lot of indiscriminately disposed excreta observed . Rains are likely to wash off indiscriminately disposed excreta into shallow wells particularly if the wells are not protected . Therefore , this may have also contributed to the contamination of the generally open shallow wells with fecal matter . Other studies have also attributed contamination of water sources to wet seasons .19 Despite the contamination of water , it was evident that it was not a common practice for the slum dwellers to boil the water , as only 42 % of those who used water from wells said they boiled drinking water . The illegal status of the slum areas in Kenya has hindered the expansion of municipal services to serve them . This has resulted to the poor being denied access to safer drinking water and proper sanitation . The results of this study suggest that water from the tap -LRB- which was from the municipal council -RRB- was safe for human consumption according to WHO guidelines .18 However , it is important to note that although the presence of thermotolerant coliforms indicates the presence of fecal contamination and potential presence of pathogens , absence of the same does not necessarily mean absence of pathogens , and further investigations would be worthwhile . Langas is not the only area with the problem of safe drinking water ; other urban centers of the developing world have experienced similar problems .19 -- 22 Similar to Langas , in the slums of Nairobi , Kenya , although wells are not a common source of water , slum residents are forced to buy tap water at exorbitant prices from vendors who operate without regulatory mechanisms .23,24 If the Millennium Development Goals of reducing by half the proportion of people without sustainable access to safe drinking water by 2015 and achieving a significant improvement in lives of at least 100 million slum dwellers by 202025 are to be met , there is a dire need for reconsideration of the slum areas in the developing world as far as water supply is concerned , as these slums are home to about 70 % of all urban residents in sub-Saharan Africa .26 However , improving the water quality at source alone may not be the ultimate solution because improving water quality at source may not always ensure a reduction in the transmission of water-related diseases . Studies27 -- 30 have shown significant deterioration in water quality between the source and the point of use . Esrey31 concluded that improving water had no health impact if the sanitation was not improved and that improving both water and sanitation together were synergistic in producing larger impacts than either alone . Although the results of this study suggest the need for provision of safer water sources , in this community and in many other slum communities with evident poor sanitary practices , intensive behavior change communication on sanitary practices is also paramount as this has been found effective in the reduction of water-borne diseases elsewhere .32 -- 35 Whereas the findings from this study are worthwhile and act as an eye opener for the situation of quality of water in the rapidly growing informal settlements in the urban areas in Kenya and in the rest of Africa , more sampling of different water sources is highly recommended . CONCLUSION It is evident that most of the sources of domestic water in Langas slum are contaminated with fecal matter and do not meet the WHO guidelines for drinking water quality . This poses a health hazard to the residents of the slum as they are at risk of water-borne diseases . The results of this study also suggest that tap water may be safer , but additional sampling is needed . The ideal intervention in the long-run may therefore be provision of adequate piped water to all slum dwellers . However , this may take sometime , and simpler interventions could be put in place in the mean time . Basic sanitary improvement may be worthwhile at the moment . Covering the shallow wells and possibly installing hand pumps or mechanical pumps at the wells could improve the situation . Basic treatment of the water at the community or household level by chemical disinfection using chlorine , filtration using simple household filters , and boiling should also be promoted . These interventions may have a great impact on the health of the slum dwellers as access to safe drinking water and basic sanitation services for populations at risk would result in 200 million/year fewer diarrheal episodes and 2.1 million/year fewer deaths caused by diarrhea .35

O O B O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O B O O O O O O O O O O B O O O O O O B I O O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O O O B O O B I O O O B O O O O O O B O O O O O O O O O B I O O O O O O O O O B O O O B O O O O O O O O O O O O B O O B O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O B O B O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B I O O O 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O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O B O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O B I O O O O O O O O O O O O O O O B O B O O O O O O O O O O O O O O O O O O O O O O O B O B O O O O O O O B I O O O B O O B O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O B O O O O O O O O O O O B B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O B O O O O O O O O O O B B O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O B O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O B O O B O O O O O O O O O O O O O O O B O O O B O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O B O O B O O O O O O O O O O O O B O O O O O O O O O O B O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O B O O O B O O O O O O O O O O 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O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B I O O O O O O O O B O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O B O O O O O O O B O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O B O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O B O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O B O O O B O O O O O O O O O B O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O B O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O B O O O O O O O B O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B I O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O B O O O O O B O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O

water
sanitation
sanitary practices
coliforms
contamination
slums
urban poor
poverty
urbanization
africa
kenya