Past Issue
Vol. 5, No. 3
May–June
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Past Issues
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Dispatches
Sentinel Surveillance for Enterovirus 71, Taiwan, 1998
Trong-Neng Wu,* Su-Fen Tsai,* Shu-Fang Li,* Tsuey-Fong Lee,* Tzu-Mei Huang,*
Mei-Li
Wang,* Kwo-Hsiung Hsu,† and Chen-Yang Shen‡
*Disease Surveillance and Quarantine Service, Ministry of Health, Taiwan, Republic of
China; †Bureau of Communicable Disease Control, Ministry of Health, Taiwan, Republic
of China; and ‡Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan,
Republic of China
| Outbreaks of enterovirus 71 have been reported around the
world since 1969. The most recent outbreak occurred in Taiwan during April-July 1998. This
hand, foot, and mouth disease epidemic was detected by a sentinel surveillance system in
April at the beginning of the outbreak, and the public was alerted. |
Enterovirus type 71 (EV71), one of the etiologic agents of epidemic hand, foot, and
mouth disease (HFMD), has been associated with febrile rash illness, aseptic meningitis,
encephalitis, and a syndrome of acute flaccid paralysis similar to that caused by
poliovirus (1,2). EV71 was identified in 1969 in the United States,
when it was isolated from the feces of an infant with encephalitis in California. By 1998,
many EV71 outbreaks had been reported around the world. In addition to the outbreak in
California in which one death was reported, four other outbreaks resulted in many fatal
cases involving clinical deterioration and death in young children (Bulgaria,
May-September 1975; Hungary, 1978; Malaysia, April-June 1997; Taiwan, April-August 1998) (3-5). To the best of our knowledge, the outbreak in Taiwan marked the
first time that an EV71 outbreak was detected by a surveillance system, which alerted the
public about the epidemic of HFMD. We describe how the EV71 outbreak was reported by a
sentinel surveillance system established in July 1989 by Disease Surveillance and
Quarantine Service (originally National Quarantine Services), Ministry of Health, Taiwan.
In this sentinel surveillance system, public health officers contact local and regional
physicians weekly to actively collect disease information. On the basis of information
collected, disease incidence trends are predicted, and, if necessary, the public is warned
during the earliest stage of disease outbreaks. Mumps, varicella, diarrhea, and
upper-tract respiratory infection are among the diseases subject to routine surveillance.
For convenience, we have established two channels of data collection: telephone interviews
and report cards mailed by physicians. Approximately 850 physicians (fewer than one tenth
of the physicians) from every county in Taiwan participate in the system: 258 in the
northern region, 211 in the central region, 296 in the southern region, and 85 in the
eastern region (Table); most of these are pediatricians, general
practitioners, and family physicians. Only a few are ear, nose, and throat specialists.
Table. Physician distribution, Sentinel
Surveillance System, Taiwan |
|
Region of
Taiwan |
Interviews |
No. cards
mailed by
physicians |
Total no.
physicians |
|
|
| Northern |
109 |
149 |
258 |
|
| Central |
27 |
184 |
211 |
|
| Southern |
175 |
121 |
296 |
|
| Eastern |
13 |
72 |
85 |
|
| Total |
324 |
526 |
850 |
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When an epidemic of fatal myocarditis was reported in Sarawak, Malaysia, in 1997, we
started to collect information regarding HFMD and vesicular pharyngitis (herpangina)
through the sentinel surveillance system. Beginning in March 1998, some physicians
reported a notable increase of cases of HFMD, vesicular pharyngitis (herpangina), and
vesicular stomatitis exanthem. Furthermore, a dramatic upsurge of HFMD was seen in
children in outpatient settings at the end of April 1998 (Figure 1).
Surveillance data provided the basis for immediate public health action. When the
number of weekly reported cases increased twofold at the end of April, the public was
informed about the epidemic of HFMD and herpangina and the threat of enterovirus infection
(May 12). Measures for preventing the spread of infection (e.g., practicing good hygiene
at all times, confining infected children at home, avoiding contact with infected
children) were advised. However, the number of reported cases still dramatically increased
to approximately 3,000 in the following week. Although some errors in reporting might have
occurred, we are confident that the reporting quality was adequate. The sentinel
physicians, who have voluntarily cooperated with us for 10 years, used a clinical case
definition of HFMD/herpangina we created when the surveillance started.
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Figure 1. Total cases of hand, foot, and mouth disease and herpangina reported from
sentinel physicians in Taiwan, March 19 to August 29, 1998.
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Figure 2. Number of hospitalizations and severe cases of hand, foot, and mouth disease
and herpangina in Taiwan, June-August, 1998.
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Monitoring incidence of the fatal and most severe cases of HFMD appeared critical;
therefore, another report system, designed for monitoring severe and fatal cases, was
established (May 29) to enroll all well-defined severe and fatal cases in 597 hospitals
and medical centers. This new system established a network of various public health
agencies, general and regional hospitals, and medical centers. The difference between the
two systems was that, while the sentinel surveillance system was physician-based, the new
system was hospital-based. Severe and fatal cases were defined as HFMD with complications,
including aseptic meningitis, encephalitis, myocarditis, acute flaccid paralysis, rapidly
deteriorating clinical course, and death. Both surveillance systems worked simultaneously
from June 1998 onward. We found that the trend peaked and declined earlier in the sentinel
system than in the hospital-based surveillance system (Figure 1, 2).
A case-control study was implemented, and enterovirus isolation data were reviewed.
Several enterovirus isolations, from patients with severe and fatal cases, were in stool
specimens, throat secretions, cerebrospinal fluid, blood, and central nervous system
tissue, including EV71, Coxsackie, and ECHO. Additional studies comparing rates of EV71
isolation in different years are in progress and will be reported separately. Most
isolated viruses were EV71 from all specimens in this epidemic. The epidemiologic,
clinical, and virologic evidence suggests an association between EV71 infection and this
epidemic of HFMD. However, the causes of the severe cases and deaths in Taiwan are yet to
be defined (5).
A physician-based sentinel surveillance system can play an important role in preventing
emerging infectious diseases. Even though the data collected may be rough, a sentinel
surveillance system can provide necessary information for monitoring communicable
diseases, guiding further investigation, and evaluating control measures, as well as early
warning for epidemics and rationale for public health intervention. Early detection of
communicable diseases and immediate public health intervention can curtail the number of
illnesses and deaths and reduce negative effects on international travel and trade (6).
Dr. Wu is vice superintendent of Municipal
Hsiao-Kang Hospital, Kaohsiung Medical College, Taiwan, Republic of China. He is also a
professor at both Kaohsiung Medical College, Kaosiung, Taiwan, and China Medical College,
Taichung, Taiwan.
Address for correspondence: Su-Fen Tsai, Division
of Disease Surveillance, Disease Surveillance and Quarantine Service, Ministry of Health,
F6, No.6, Lin Shen S. Rd., Taipei, Taiwan, R.O.C.; fax: 886-2-23945312; e-mail: sftsai@net.dsqs.gov.tw.
References
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Enterovirus type 71 infection: a varied clinical pattern sometimes mimicking paralytic
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Enterovirus 71 infection and neurologic disease—United States, 1977-1991. J
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Epidemiological, clinical, and pathomorphological characteristics of epidemic
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- Centers for Disease Control and Prevenetion.
Deaths among children during an outbreak of hand, foot, and mouth disease—Taiwan,
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