Emerging Infectious Diseases
[Volume 6 No.2 / March - April 2000]

Dispatches

The Impact of Health Communication and Enhanced Laboratory-
Based Surveillance on Detection of Cyclosporiasis Outbreaks in
California

Janet C. Mohle-Boetani,* S. Benson Werner,* Stephen H.
Waterman,* and Duc J. Vugia*
*California Department of Health Services, Berkeley, California,
USA; and The California Emerging Infections Program,
Berkeley, California, USA

We investigated the timing of diagnosis, influence of media
information on testing for Cyclospora, and the method used to
identify cases during eight cyclosporiasis outbreaks in California in
spring of 1997. We found that Internet information, media reports,
and enhanced laboratory surveillance improved detection of these
outbreaks.

Cyclospora cayetanensis, a recently identified coccidian parasite of
humans (1), causes explosive watery diarrhea that can persist for
several weeks (2). The oocysts cannot be detected by standard ova
and parasite testing; methods specific for Cyclospora include
modified acid-fast or other stains, autofluorescence with ultraviolet
epifluorescence microscopy, and wet mount under phase-contrast
microscopy (3). The infection can be treated with trimethoprim-
sulfamethoxazole (TMP-SMX) (4). Eight outbreaks in California
were among the 41 event-associated clusters of cyclosporiasis
associated with Guatemalan raspberries identified in the United
States and Canada in 1997 (5). We examined factors contributing
to the identification of outbreaks of this emerging infectious
disease. The detection of outbreaks was enhanced by Internet
information that patients brought to their physicians, media reports,
and enhanced laboratory-based (ELB) surveillance. ELB
surveillance, part of the California Emerging Infections Program
(EIP), is a cooperative agreement between the California State
Health Department, the University of California Berkeley School
of Public Health, selected local counties, and the Centers for
Disease Control and Prevention.

The Study

An outbreak of cyclosporiasis was defined as diarrhea (three or
more loose stools per day for at least 3 days) in two or more
persons who shared a meal and became ill within 2 weeks, and
laboratory confirmation of Cyclospora infection in at least one
person. The first person with laboratory-confirmed Cyclospora
infection identified in an outbreak was designated the index
patient.

We interviewed each index patient about the onset of symptoms
and medical care, and we reviewed laboratory records to determine
the date of testing for Cyclospora. Through information that we
gathered from patients and their physicians, we determined the
reason for testing for Cyclospora (e.g., symptoms alone, symptoms
and media attention, or symptoms and Internet information). We
interviewed all guests at a wedding reception (event 3, Table) to
determine the proportion of ill persons who sought medical
attention, submitted stool specimens tested specifically for
Cyclospora, and received recommended treatment for Cyclospora
infections, all with respect to timing of media coverage of
Cyclospora outbreaks.

To assess the impact of ELB surveillance on outbreak detection,
we determined the proportion of outbreaks identified by ELB
surveillance. All 22 laboratories in eight participating counties in
northern California submitted biweekly or monthly laboratory
reports on Cyclospora to EIP. EIP staff then forwarded case
information to the local health departments for follow-up. The
eight index patients were tested for Cyclospora infections a median
of 18.5 days after symptom onset (range 3-39 days, Table); 6
(75%) were diagnosed >14 days after onset (events 1-6, Table).
The two index cases diagnosed within 1 week of disease onset
occurred after media announcements about clusters of
cyclosporiasis in the United States were widespread in late May
1997 (events 7 and 8, Table). Testing for 6 (75%) index patients
was apparently prompted by this media coverage (events 3-8,
Table). After reading newspaper articles, three index patients
(events 3, 5, and 8) obtained information on the diagnosis and
treatment of Cyclospora from Internet searches, brought this
information to their physicians, and requested testing. One index
patient (event 4) read about other clusters in the United States in
the newspaper and requested testing from her physician. Another
index patient (event 6) suspected that she and a group of friends
had Cyclospora infections after reading a list of symptoms in a
newspaper article and reported this cluster to the local health
department, which then recommended testing for Cyclospora. One
index patient (event 7) was tested by a clinician who watched a
television report about cyclosporiasis the morning of the patient's
visit to the clinic.

Table. Event-associated outbreaks of cyclosporiasis, California,
1997

Within 2 weeks after a wedding party in May (event 3, Table), 30
(65%) of 46 guests had diarrhea; within 3 weeks, 13 sought
medical attention. Although seven patients submitted stool
specimens, none was tested for Cyclospora. Approximately 3
weeks after the wedding, several ill guests and the bride (who had
not eaten the mixed berry dessert and was not ill) read media
accounts of a Cyclospora outbreak that had occurred in Reno,
Nevada. They recognized similar symptoms in themselves or their
family members, obtained more information about Cyclospora
from the CDC Web site, and distributed it to other guests. All 16
guests who brought that Internet information to their physicians
received appropriate treatment with TMP-SMX; symptoms
resolved promptly (typically within 24 hours). Three of these 16
guests were tested for Cyclospora, and stool specimens were
positive.

In three outbreaks (events 1, 2, and 6, Table), the index patient was
tested after a suspected foodborne outbreak had been reported to
the local health department by symptomatic patients (events 1 and
6, Table) or an infectious disease specialist (event 2, Table). Index
patients from these three outbreaks were identified by the health
department within 1 day of their laboratory verification.

In six outbreaks, patients lived in counties with ELB surveillance;
5 (83%) of these outbreaks were detected by interviewing index
patients with positive specimens identified through ELB
surveillance (events 3, 4, 5, 7, and 8, Table). The health
departments were notified of 4 of the 5 index cases detected
through ELB surveillance 3 to 6 days after laboratory confirmation.
The detection of these outbreaks was delayed primarily because the
diagnosis of cases was delayed, rather than because health
departments were not notified of positive laboratory results
(Table). The delays in diagnosis were due to delays in seeking
medical care and receiving evaluation by a physician. For example,
the index patients in outbreaks 3 and 5 sought medical attention
after > 14 days of symptoms, after learning about other outbreaks
of cyclosporiasis, conducting Internet searches on diagnosis and
treatment, and bringing this information to their physicians; both
were tested promptly. In contrast, the index patient in outbreak 6
was tested 24 days after seeking medical attention, in response to a
recommendation by the local health department; this cluster of
illnesses was reported to the health department when some of the
patients learned about the cyclosporiasis outbreaks in the news.

The wedding outbreak investigation (event 3) best illustrates delays
in clinician evaluations and effects of Internet information
provided by patients on proper diagnosis and treatment (6).
Thirteen (43%) of ill persons consulted physicians, and 54% of
these submitted stool specimens; however, disease diagnosis was
delayed because none of the physicians ordered specific laboratory
testing that could identify Cyclospora (3). Patients were not tested
until media attention about other clusters of cyclosporiasis in the
United States led the bride and ill guests to conduct Internet
searches.

Conclusions

The role that the media and Internet information played in testing
for Cyclospora in these outbreaks was striking. Most index patients
prompted their physicians to test for Cyclospora by providing them
with Internet or media information. At least seven of the ill
wedding guests contacted their physicians several times over a 2-
to 3-week period but were not tested or treated properly until they
provided information on Cyclospora. The two index patients who
did not have a delay in diagnosis were prompted by widespread
media reports to seek both Internet information on Cyclospora and
medical attention. In the only instance in which appropriate testing
was ordered without prompting by the patient or the health
department, the physician had watched a television report on
cyclosporiasis that morning.

Several factors can contribute to delays in testing for Cyclospora,
and all of these factors were noted in the wedding outbreak.
Persons with diarrheal illnesses often do not seek medical
attention; 57% of ill persons in the wedding outbreak did not.
Since Cyclospora is a new infection, many physicians are not
familiar with its symptoms and treatment. Physicians often do not
request testing of stool; 46% of ill persons who sought medical
care in the wedding outbreak did not have any stool testing.

Detection of cases not only influences detection of clusters but also
prompts appropriate medical treatment with TMP-SMX. When a
clinical decision is made to assess a patient for a parasitic
gastrointestinal infection (e.g., patients with prolonged diarrhea),
clinicians should order both routine ova and parasite examination
and specific testing for Cyclospora and Cryptosporidium.
Laboratory-confirmed cases should be promptly reported so that
outbreaks can be detected and investigated, ongoing transmission
can be interrupted, and other ill persons can be provided with
effective treatment. Because symptoms can be prolonged,
investigation even 1 month after a common event can lead to
effective treatment.

Cyclospora is not yet reportable in California; however, clinicians
are required to report all unusual diseases and outbreaks to the
local health departments. Nevertheless, diseases that are not
reportable are rarely reported. Therefore, Cyclospora outbreaks
identified through ELB surveillance (83% of outbreaks that
involved residents of the counties with this surveillance system)
might not have been detected without enhanced surveillance.

Acknowledgments

We thank Gwen Bell, Amy Bellomy, Louise Gresham, Anthony
Marfin, Beth Schultz, and Sirlura Taylor for providing information
on index patients; Louise Gresham, Carol Greene, Sara Cody, Jon
Rosenberg, and Robert Murray for conducting patient interviews;
Judy Rees and Joelle Nadel for providing information from the
California Emerging Infections Program; and Barbara Herwaldt for
her thoughtful review of the manuscript.

Dr. Mohle-Boetani is a medical epidemiologist in the Disease
Investigations and Surveillance Branch of the Division of
Communicable Disease Control, California Department of Health
Services, Berkeley, California. Her areas of expertise include
outbreak investigation, cost-effectiveness analysis, and surveillance
of infectious diseases.

Address for correspondence: Janet Mohle-Boetani, Disease
Investigations Section, Disease Investigation and Surveillance
Branch, Division of Communicable Disease Control, California
Department of Health Services, 2151 Berkeley Way, Room 708,
Berkeley, CA 94704, USA; fax: 510-540-2570; e-mail:
jmohlebo@dhs.ca.gov.

References

1. Ortega YR, Sterling CR, Gilman RH, Vitaliano AC, Diaz F.
Cyclospora speciesa new protozoan pathogen of humans. N Engl
J Med 1993;328:1308-12.
2. Soave R. Cyclospora: an overview. Clin Infect Dis 1996;23:429-
37.
3. Eberhard ML, Pieniazek NJ, Arrowood MJ. Laboratory
diagnosis of Cyclospora infections. Arch Pathol Lab Med
1997;121;792-7.
4. Hoge CW, Shlim DR, Ghimire M, Rabold JG, Pandey P, Walch
A, et al. Placebo-controlled trial of co-trimoxazole for Cyclospora
infections among travelers and foreign residents in Nepal. Lancet
1995;346:691-3.
5. Herwaldt BL, Beach MJ, Cyclospora Working Group. The
return of Cyclospora in 1997: another outbreak of cyclosporiasis in
North America associated with imported raspberries. Ann Intern
Med 1999;130:210-20.
6. Silberg WM, Lundberg GD. Musacchio RA. Assessing,
controlling, and assuring the quality of medical information on the
Internet. JAMA 1997;277:1244-5.

Emerging Infectious Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention
Atlanta, GA

URL: http://www.cdc.gov/ncidod/EID/vol6no2/ascii/mohleboetani.txt

Please note that figures, equations, and tables are not available 
in ASCII format.  Many symbols do not convert to ASCII.