—from the Epidemiological Bulletin, Vol. 21 No. 2, June 2000—
Update on Yellow Fever in the Americas
Yellow fever continues to be an important public health problem
in the Americas. Between 1985 and 1999, Bolivia, Brazil, Colombia, Ecuador,
Peru, Venezuela and French Guiana reported 2,935 cases and 1,764 deaths (See
Table 1). During this period, more than 80% of all yellow
fever reports in the American Region came from Bolivia and Peru. In 1999, Bolivia,
Brazil and Peru accounted for 33%, 36% and 27% of all cases, respectively. However,
from January to May 2000, a total of 66 confirmed cases were reported in Brazil,
which represent more than 90% of all the cases notified in the Region during
this period. Reports from the Brazilian Ministry of Health show that most of
those cases come from the State of Goiás and neighboring States, where an extensive
epizootic has been taking place since the beginning of the year (see Table
2).
All cases notified in the Region since the 1940s have been of the jungle form
of yellow fever, transmitted by mosquitoes of the genus Haemagogus. However,
the overwhelming spread of the Aedes aegypti mosquito threatens to re-urbanize
the disease. The seriousness of the current yellow fever situation in the Region
demands a firm commitment by the countries to a strong and effective strategy
for controlling the disease. The Pan American Health Organization (PAHO)’s recommendations
focus on the prevention of its re-urbanization, through surveillance, vaccination
and vector control.
The establishment of a sensitive surveillance system is critical to the control
and prevention of yellow fever. Currently notified cases tend to be of the severe
clinical form of the disease, and therefore correspond to only a fraction of
the total number of yellow fever virus infections, since as much as 50% of all
cases can be asymptomatic.
In order to provide immediate protection to residents in enzootic areas and
to prevent the introduction of yellow fever into nearby urban areas infested
with Aedes aegypti, high levels of vaccination should be maintained among
individuals living in both areas. During its Seventh Plenary Session in 1997,
PAHO’s Directing Council exhorted its Member States to include yellow fever
vaccine in their national immunization programs in all areas at risk of transmission
of the disease. The countries and territories that have included universal children
immunization against yellow fever are Trinidad and Tobago, Guyana and French
Guiana. Brazil, Ecuador and Peru have given priority to the immunization of
children in enzootic areas. Trinidad and Tobago and Guyana have implemented
“catch-up” campaigns in all age groups in the entire country, and Brazil and
Ecuador have used the same strategy for enzootic areas and regions with a high
risk of transmission of the disease. Peru, Bolivia, Suriname and Venezuela have
developed plans to introduce the yellow fever vaccine in their children vaccination
schedule, as well as the vaccination of all age groups in enzootic areas.
Present day control strategies against the urban vector Aedes aegypti are
based primarily on the reduction of breeding sources through their elimination.
Social communication, community participation and health education are fundamental
elements in these strategies. Insecticides are widely used where there are high
vector population densities.
Table 1: Reported cases and deaths from yellow
fever in the Region of the Americas, by country, 1985-2000
| |
1985-1995
|
1996
|
1997
|
1998
|
1999*
|
2000*
|
| Country |
Cases
|
Deaths
|
Cases
|
Deaths
|
Cases
|
Deaths
|
Cases
|
Deaths
|
Cases
|
Deaths
|
Cases
|
Deaths
|
| Bolivia |
424
|
319
|
30
|
21
|
63
|
47
|
57
|
39
|
68
|
33
|
1
|
0
|
| Brazil |
202
|
88
|
15
|
12
|
3
|
3
|
34
|
15
|
75
|
28
|
66
|
35
|
| Colombia |
55
|
47
|
8
|
4
|
5
|
4
|
1
|
0
|
2
|
2
|
|
|
| Ecuador |
45
|
29
|
8
|
8
|
31
|
4
|
3
|
1
|
5
|
3
|
|
|
| F. Guiana |
-
|
-
|
-
|
-
|
-
|
-
|
1
|
1
|
-
|
-
|
|
|
| Peru |
1431
|
914
|
86
|
34
|
44
|
20
|
165
|
49
|
56
|
33
|
2
|
1
|
| Venezuela |
2
|
1
|
-
|
-
|
-
|
-
|
15
|
4
|
1
|
1
|
|
|
|
Total
|
2159
|
1398
|
147
|
79
|
146
|
78
|
276
|
109
|
207
|
100
|
69
|
36
|
* Provisional data
PAHO. Division of Vaccines and Immunization.
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Table 2: Confirmed cases of yellow fever in Brazil,
January-May 2000
| State |
Cases
|
Deaths
|
| Amazonas |
1
|
0
|
| Bahia |
8
|
2
|
| Brasilia, D.F. |
1
|
1
|
| Goiás |
43
|
22
|
| Mato Grosso |
4
|
3
|
| Minas Gerais |
1
|
1
|
| Sao Paulo |
2
|
2
|
| Tocantins |
6
|
4
|
|
Total
|
66
|
35
|
CENEPI-FUNASA-Ministry of Health of Brazil.
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For the case definition of yellow fever, select this link.
Source: PAHO. Division of Vaccines and Immunization and Division of Disease Prevention and Control.
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Epidemiological Bulletin, Vol. 21 No. 2, June 2000
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