data on all campylobacter isolates obtained from fecal or lower gastrointestinal tract samples , reported in england and wales from 1990 through 2007 , were extracted from the national laboratory database ( labbase ) and stored in a microsoft access ( microsoft corp . ,
cases were assigned to 10-year age groups and to geographic areas on the basis of laboratory location ( northern , mid - country , southern ) .
the season was assigned on the basis of the earliest available specimen date ( spring , march  may ; summer , june  august ; autumn , september 
data on cases of cryptosporidiosis and nontyphoidal salmonellosis for the same period were extracted , grouped , and categorized and manipulated as above for comparative purposes .
denominator data for england and wales for the same period were obtained from the office for national statistics .
data were analyzed in microsoft excel 2003 and stata version 10 ( statacorp , college station , tx , usa ) .
estimates of incidence per 100,000 population were calculated throughout ; relative risks ( rr ) and 95% confidence intervals ( cis ) were calculated as required . from 1990 through 2007 in england and wales , 838,436 cases of campylobacter infection were reported ; patient age was available for 810,632 case - patients ( 96.7% ) . from 1990 through 1999 , incidence increased in all age groups ( figure 1 ) , but the increase was proportionate to increasing age ( 09 years of age rr 1.07 [ 95% ci 1.031.10 ] ; 1019 years rr 1.47 [ 95% ci 1.411.55 ] ; 2059 years rr 1.78 [ 95% ci 1.751.81 ] ; > 60 years rr 2.51 [ 95% ci 2.412.61 ] ) . from 2000 through 2004 , incidence declined in all age groups .
however , although the degree of decline was similar for those 09 years of age ( rr 0.77 [ 95% ci 0.740.8 ] ) , 1019 years ( rr 0.73 [ 95% ci 0.700.76 ] ) , and 2059 years ( rr 0.75 [ 95% ci 0.740.76 ] ) , for patients > 60 years of age , the degree of decline was significantly lower ( rr 0.88 [ 95% ci 0.860.91 ] ;  p<0.001 ) .
finally , although the incidence increased only moderately among those 1019 years of age ( rr 1.02 [ 95% ci 0.981.07 ] ) and 2059 years ( rr 1.04 [ 95% ci 1.031.06 ] ) from 2005 through 2007 , greater increases were observed for those 09 years ( rr 1.12 [ 95% ci 1.081.17 ] ) and those > 60 years ( rr 1.33 [ 95% ci 1.291.36 ] ) . during the surveillance period , therefore , the incidence among patients > 60 years of age , compared with the incidence among younger patients , increased markedly ( rr 0.45 [ 95% ci 0.440.47 ] in 1990 to rr 1.17 [ 95% ci 1.151.19 ] in 2007 ) .
this effect was observed for campylobacteriosis in both sexes , in 3 geographic areas of england and wales , and in all 4 seasons , but was not observed for nontyphoidal salmonellosis or cryptosporidiosis ( figure 2 ; technical appendix ) .
incidence of laboratory - reported campylobacteriosis , england and wales , by age group , 19902007 .
relative incidence of campylobacteriosis by sex , region , and season , compared with rates of salmonellosis and cryptosporidiosis , among patients > 60 years of age , england and wales , 19912007 .
northern , northwest , northeast , as well as yorkshire and the humber regions ; mid - country , wales , west midlands , east midlands , and east of england regions ; southern , london as well as southeast and southwest regions .
salmonellosis includes nontyphoidal salmonellae , with age data available for 356,270 of 380,915 case - patients ( 94% ) ; cryptosporidiosis includes age data for 76,462 of 79,808 case - patients ( 96% ) .
we report a striking change in the population at risk for campylobacteriosis in england and wales , which is independent of gender , geography , or season .
the absence of a similar change in the age distribution of laboratory - reported salmonellosis or cryptosporidiosis from the same population suggests that this is unlikely to be a surveillance artifact .
campylobacter infections are rarely typed beyond the genus level in england and wales , so infections are routinely reported as campylobacter species .
therefore , changes in the incidence of the various species that constitute this broad case definition could possibly explain some of the altered disease pattern reported .
for example , infections caused by certain species ( e.g. , c. fetus ) are more often associated with coexisting conditions that might occur more frequently in the elderly .
first , isolation methods used in england and wales favor the growth of c. jejuni and c. coli ( 4,5 ) over that of other species , including c. fetus . furthermore , c. fetus normally causes systemic infections detected through blood culture , and the proportion of blood to fecal isolations of campylobacter species in patients > 60 years of age reported in england and wales remained constant from 1990 through 1999 ( 275/58,139 fecal isolations ; 0.47% ) , from 2000 through 2004 ( 185/44,349 ; 0.42% ) , and from 2005 through 2007 ( 135/31,637 ; 0.42% ) ( health protection agency , unpub . data ) . when disease incidence was ranked according to specific population group , children 09 years of age had the highest ranking in 1990 , but by 2007 , incidence for this age group ranked seventh of 9 age groups .
this finding led to the hypothesis that the introduction and increased utilization of the national health service s nhs direct ( a 24-hour telephone , online , and interactive digital tv service , which provided health advice and information ) at this time had a  triage effect  on those seeking care for children in this age group .
the 2 events are correlated in time ( initial nhs direct pilot sites began taking calls in march 1998 ; by april 1999 , 40% of the population of england had access , and by november 2000 , the service was available throughout england and wales ) , nhs direct has had a demonstrable negative effect on the use of general practice ( 7 ) , and infants and young children are overrepresented among calls to nhs direct about gastrointestinal conditions ( 8) .
the second infectious intestinal disease study in england , currently under way ( 9 ) , will provide further information upon which to assess this hypothesis , which is not readily testable by using laboratory data . by far the most striking
finding of this study is the emergence of older persons as the population most at risk for campylobacteriosis in england and wales .
although the elderly were not the only group at risk in 2007 ( because of increasing incidence ) , the overall trend singles them out as the main emerging at - risk group ( the increase in other age groups requires continued monitoring , however ) .
the pattern of infection in older patients is perhaps predictable , given the similar pattern for incidence of listeriosis in england and wales since 2001 ( 10 ) . as life expectancy increases in the united kingdom ,
the number of persons living with chronic conditions is likely to increase ; these factors suggest that the incidence of campylobacteriosis in older persons will continue to increase in the future .
therefore , risk factors for campylobacter infection specific to older uk residents must be identified .
relative incidence of campylobacter infection in each year compared with that in 1990 among patients > 60 years of age infected with selected gastrointestinal pathogens , england and wales , 1991 - 2007
 to explore hypotheses for age - related changes in the incidence of campylobacter infections in england and wales during 19902007 , we analyzed electronic laboratory data . 
 disease incidence was reduced among children , and the greatest increase in risk was for those > 60 years of age . 
 risk factors for campylobacteriosis in the elderly population should be identified . 