Epidemiological update: Yellow fever outbreak in Brazil, 6 April 2017 Archived

​Yellow fever is a mosquito-borne viral infection present in some tropical areas of Africa and South America.ellow fever is a mosquito-borne viral infection present in some tropical areas of Africa and South America. Yellow fever is a mosquito-borne viral infection present in some tropical areas of Africa and South America.

In South America, there are two transmission cycles of yellow fever:

- A sylvatic cycle, involving transmission of the virus between Haemagogus or Sabethes mosquitoes and primates. The virus is transmitted by mosquitoes from primates to humans when humans are visiting or working in the forest.

- An urban cycle, involving transmission of the virus between Aedes aegypti mosquitoes and humans. The virus is usually introduced in an urban area by a viraemic human who was infected in the forest.

Brazil has been experiencing an outbreak of yellow fever since December 2016. The outbreak was notified on 6 January 2017. From the beginning of the year to 3 April 2017, the World Health Organization (WHO) has also reported cases in Bolivia, Colombia, Ecuador, Peru and Suriname.

Weekly summary

Between 23 March and 5 April 2017, Brazil has reported 90 additional confirmed cases and has discarded 459 suspected cases of yellow fever.

According to WHO, yellow fever virus transmission is expanding towards the Atlantic coast in areas previously not at risk. WHO has updated the yellow fever vaccination recommendations for international travellers to Brazil, expanding to more than 150 new municipalities in the state of Bahia including Salvador, urban areas of Campinas in the state of São Paulo, and the entire state of Rio de Janeiro.

Epidemiological summary

Brazil: Between 6 January and 5 April 2017, Brazil has reported 1 036 cases (450 suspected and 586 confirmed), including 239 deaths (49 suspected and 190 confirmed).

States reporting suspected and confirmed autochthonous cases:

• Minas Gerais has reported 713 cases (287 suspected and 426 confirmed), including 176 deaths (38 suspected and 138 confirmed).
• Espírito Santo has reported 240 cases (98 suspected and 142 confirmed), including 49 deaths (six suspected and 43 confirmed).
• Rio de Janeiro has reported 28 cases (19 suspected and nine confirmed), including two deaths (one suspected and one confirmed).
• São Paulo has reported 13 cases (eight suspected and five confirmed), including five deaths (one suspected and four confirmed).
• Pará has reported nine cases (five suspected and four confirmed), including five deaths (one suspected and four confirmed).

States reporting suspected autochthonous cases:

The following states have reported suspected cases: Paraná (9), Bahia (8), Santa Catarina (6), Rio Grande do Sul (4), Amapá (1), Distrito Federal (1), Goiás (1), Mato Grosso (1), Mato Grosso do Sul (1) and Tocantins (1). Two suspected deaths were reported in Santa Catarina (1) and Tocantins (1).

Other countries in South America:

From week 1 to 13 of 2017, five other countries have reported suspected or confirmed cases of yellow fever: Bolivia (1), Colombia (1), Ecuador (1), Peru (9) and Suriname (1).

ECDC assessment

The ongoing outbreak should be carefully monitored, as the establishment of an urban cycle of yellow fever would have the potential to quickly affect a large number of people. EU/EEA citizens who travel to, or live in, areas where there is evidence of yellow fever virus transmission should check their vaccination status and obtain medical advice about being vaccinated against yellow fever.

In Europe, Aedes aegypti, the primary vector of yellow fever in urban settings, is present in Madeira. Recent studies have shown that Aedes albopictus can potentially transmit the yellow fever virus. However, the risk of the virus being introduced into local competent vector populations in the EU through viraemic travellers from Brazil is considered to be very low, as the current weather conditions in Europe are not favourable for vector activity.

Actions

ECDC closely monitors this event in collaboration with the World Health Organization.

ECDC published a rapid risk assessment on the outbreak of yellow fever in Brazil on 26 January 2017 and a rapid risk assessment on yellow fever among travellers returning from South America on 15 March 2017. ECDC also produces a map for travel advice.