Epidemiological Update - Yellow Fever - 23 March 2017

Situation summary in the Americas

Since epidemiological week (EW) 1 to EW 11 of 2017, Brazil, Colombia, Ecuador, Peru, the Plurinational State of Bolivia, and Suriname have reported suspected and confirmed yellow fever cases.

Following is a summary of the situation in Brazil and Peru.

In Brazil, since the beginning of the outbreak in December 2016 to 17 March of 2017, there were 1,561 cases of yellow fever reported, of which 28.7% were laboratory-confirmed (n=448),

16.9% were discarded (n=263), and 54.8% (n=850) remain under investigation as suspected cases, including 264 deaths (144 confirmed, 10 discarded, and 110 under investigation). The case fatality rate (CFR) is 32% among confirmed cases.

According to the probable site of infection, the cases were reported in 188 municipalities, of which 49.4% are in the state of Minas Gerais. This state, furthermore, accounts for the majority of suspected and confirmed cases (1,016), followed by Espírito Santo (243), São Paulo (15),
Bahia (8), Tocantins (6), Goías (3), and Rio de Janeiro (3). 1 The confirmed cases are distributed in four states: Minas Gerais (349), Espírito Santo (93), São Paulo (4), and Rio de Janeiro (2).
The cases reported in the state of Rio de Janeiro are three2 men that reside in the rural area of the municipality of Casimiro de Abreu and have no history of travel to states with confirmed circulation of the yellow fever virus.

In the states of Minas Gerais and Espírito Santo, the downward trend in reported cases observed in the last five weeks continues (Figures 1 and 2). Figure 1 illustrates the trend of reported cases in the four regional health units which account for 96% of the cases reported in Minas Gerais.
There is possibility of a change in the yellow fever transmission cycle in this current outbreak, however, to date Aedes aegypti has not been reported to have a role in transmission.

Confirmed cases have been reported in municipalities near large urban areas in the states of Espírito Santo and Minas Gerais; this combined with the confirmation of epizootics and notification of suspected cases in the municipality of Vitoria, Espírito Santo, represent a high risk for a change in the transmission cycle.

With regard to the confirmed fatal cases and their probable site of infection, 118 were in the state of Minas Gerais, 3 in the state of São Paulo, 22 in the state of Espírito Santo, and one in Rio de Janeiro. In decreasing order, the CFR among suspected and confirmed cases by state is 75% in São Paulo, 34% in Minas Gerais, 33% in Rio de Janeiro, and 24% in Espírito Santo.

The thematic maps presented in Figure 3 incorporate in superimposed layers the following elements: in red, the municipalities where human cases have been confirmed, and in red hatched pattern (with red lines), the municipalities where epizootics have been confirmed. In the states of Minas Gerais and Espírito Santo, the overlap of the two layers can be observed.

On the other hand, in blue, the municipalities with suspected human cases under investigation, and in blue hatched pattern (with blue lines), epizootics under investigation. It is observed that the states of Alagoas, Mato Grosso do Sul, Para, Paraíba, Paraná, Pernambuco, Rio Grande do Sul, Rondônia, Santa Catarina, and Sergipe, have only reported epizootics under investigation and no human cases.

Since the last yellow fever Epidemiological Update3 up to 17 March 2017, 21 new epizootics were reported in nonhuman primates (NHP). Since the beginning of the outbreak up to 17 March 2017, a total of 1,249 NHP epizootics were reported, of which 389 were yellow fever confirmed, 382 remain under investigation, and 12 were discarded.

Epizootics in NHP were reported in the Federal District and in the states of Alagoas, Bahia,
Goiás, Espírito Santo, Mato Grosso do Sul, Minas Gerais, Pará, Paraíba, Paraná, Pernambuco,
Rio Grande do Norte, Rio Grande do Sul, Rondônia, Santa Catarina, São Paulo, Sergipe, and Tocantins.

Reports of epizootics are currently under investigation in the states of Mato Grosso do Sul (bordering Bolivia and Paraguay), Santa Catarina (bordering Argentina), Rio Grande do Sul (bordering Uruguay and Argentina), Rondônia (bordering Bolivia), Pará (bodering Guyana and Suriname), and Paraná (bordering Argentina and Paraguay), this represents a risk of spread of the virus to the bordering countries, especially in areas with similar ecosystems.

In Peru, as of EW 10 of 2017, a total of 14 cases of yellow fever were reported, of which three were confirmed, 5 remain classified as probable, and 6 were discarded; including two deaths.
The confirmed cases were reported by the department of Ayacucho and the 5 probable cases by the department of Amazonas (2), San Martin (1), Madre de Dios (1), and Pasco (1).