International Notes Yellow Fever in the Americas,
1981 and 1982
For the years 1981 and 1982, five countries in the Americas
(Bolivia, Brazil, Colombia, Ecuador, and Peru) reported 368 cases
of
jungle yellow fever, slightly more than the 324 of the preceding 2
years. Bolivia and Peru accounted for 84.8% (312) of the cases;
Brazil, 12.5% (46); and Colombia, 2.2% (eight); two cases were
detected in Ecuador. Deaths from yellow fever in those years
totaled
183.
The highest monthly number of cases occurred in the first half
of
each year, with a peak in March. This may reflect increased rural
and
forest labor practices during the first months of the year among
susceptible populations in yellow fever enzootic areas. Another
factor may be higher densities of Haemagogus mosquitoes--the main
jungle yellow fever vector in the Americas--during the rainy
season.
All cases reported in 1981 and 1982 occurred in known endemic
areas, except one epidemic in 1981 in Rincon del Tigre, Department
of
Santa Cruz, Bolivia, that accounted for approximately 50% of
Bolivia's
cases that year. The last confirmed outbreak in the Department of
Santa Cruz occurred in the late 1940's, illustrating the virus'
potential to reappear after long periods of inactivity. A
1980-1981
outbreak in Brazil involved the states of Goias, Mato Grosso, and
Mato
Grosso de Sul. This epidemic and previous epidemics in the State
of
Goias may reflect virus movement from the enzootic areas of the
Amazon
Region.
Age and sex data, available for 347 patients, showed that 79%
(275) were male. Most patients (79%) were between 15 and 34 years
of
age; no patients were under 1 year; and all but one case in the
1-4-year age group occurred in the Rincon del Tigre region. All
Brazilian patients were over 15 years of age. This age and sex
distribution is consistent with patterns of disease acquired in the
jungle.
No urban cases of yellow fever have been documented in the
Americas for the past 4 decades, although several patients with
jungle-acquired disease have been hospitalized in A.
aegypti-infested
towns during this period. Although surveillance in remote areas
may
be inadequate, a general decline in incidence of the disease in the
Amazon Region appears to have resulted from intensification of
vaccination programs throughout endemic areas. About three million
doses of 17D vaccine are administered in Brazil annually (3,300,000
in
1981).
Because of continuing yellow fever incidence and the
reinfestation
of some infected areas, the Pan American Health Organization (PAHO)
has recently convened several technical meetings to examine the
problem. Recommendations from these meetings include: 1) improving
surveillance activities; 2) strengthening direct cooperation among
affected countries; 3) promptly disseminating information to member
countries; 4) increasing production of 17D vaccine; and 5)
promoting
assistance among member countries, either directly or through PAHO,
with bilateral loans and grants and the provision of equipment,
materials, and technical advisory services.
Reported in PAHO Epidemiological Bulletin 1983;4(1):1-5.
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