What to Know About Brazil's Yellow Fever Outbreak

The Aedes aegypti mosquito, the main vector of yellow fever in Brazil
The Aedes aegypti mosquito, the main vector of yellow fever in Brazil | © James Gathany, courtesy of Centers for Disease Control / Flickr
Euan Marshall

Visitors to the north and center-west regions of Brazil have long been recommended to take a yellow fever vaccination before traveling. However, thanks to a recent outbreak of the disease in the populous south-east, the World Health Organization now recommends the vaccine for all areas of the country, including the massive cities of São Paulo and Rio de Janeiro. Here’s everything you need to know before planning your visit to Brazil.

Yellow fever is traditionally only a worry in the rainforest and rural areas of Brazil, but this recent outbreak has seen it arrive on the doorstep of the country’s massive south-east state capitals. Scientists have put this spread down to either the migration of mosquito populations from the north, or infected individuals traveling to the south-east and being bitten by local mosquitos, passing on the virus.

State parks across São Paulo, Rio de Janeiro, Minas Gerais and Espírito Santo have been closed in an attempt to slow the spread of the disease, while wild primate populations have been greatly affected.

In the state of Minas Gerais alone, there have been 365 confirmed cases of the disease since the beginning of the outbreak, with 133 deaths.

The yellow fever virus is transmitted to humans and primates by bites from infected female mosquitos, usually the Aedes aegypti species (also responsible for spreading other such diseases as dengue fever, Zika and chikungunya). These insects usually hunt during the early morning and evening, so make sure your windows are well sealed during the night.

The Aedes aegypti mosquito, the main vector of yellow fever in Brazil

Yellow fever symptoms take three to five days to appear and when they do they are initially quite mild, consisting mainly of fever, headaches, muscle pain and nausea. After a short improvement, infected individuals may see their symptoms return and in a severe manner, with stomach pain, very high fever and jaundice caused by liver damage. In cases where the symptoms return, 50% of yellow fever patients die within two weeks. There is no treatment for yellow fever, though the symptoms themselves may be treated, giving the patient a better chance of survival.

Though vaccination is recommended for these areas, the risk of yellow fever transmission in large Brazilian cities (such as São Paulo, Rio de Janeiro and Belo Horizonte) is very low, especially in the expanded centers of these cities, due to the small number of Aedes aegypti mosquitos. However, as soon as you venture into the countryside or down to the coast, the risk increases significantly. Many of the idyllic holiday destinations on the south-east’s Litoral Norte coastline have significant numbers of Aedes aegypti, meaning you should stay at home if you haven’t been vaccinated.

The idyllic Ilha Grande has become a risk area for yellow fever

Yellow fever vaccines are proven to be extremely effective, with the human body creating a sufficient immunity after 10 days and full immunity after one month. Around 5% of people develop some sort of side effect from the vaccine, usually fever, headache and muscle pain, symptoms which normally appear around five days after receiving the vaccination and pass naturally. Serious complications are extremely rare, with approximately 1 in 300,000 people developing yellow fever itself.

The yellow fever vaccination certificate is not a requirement for obtaining a Brazilian entry visa and in theory you could get the vaccination upon arrival. However, the scale of the outbreak has caused a shortage of vaccine, meaning you would face huge queues at health centers. Furthermore, due to the unprecedented demand, Brazil is only giving out smaller doses of the vaccine, meaning you would need to take a booster shot after eight years.

A child receiving a yellow fever vaccination in São Paulo

Despite the panic in the Brazilian press, the yellow fever outbreak is no reason for alarm for tourists and should not stop anyone from visiting this magical country. Just get the full vaccination at least 10 days before your trip, and you’ll be immune for life.

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