SAO PAULO (Reuters) – Health authorities launched a yellow fever vaccination campaign on the north side of Brazil’s largest city over the weekend after a dead monkey was found infected with the disease, state and city officials said on Monday.
Two parks were closed following confirmation that one of five monkeys found dead on Friday had yellow fever, raising fears of an outbreak of the illness in metro Sao Paulo, home to 23 million people.
Brazil is undergoing its worst yellow fever outbreak in decades. The virus has killed at least 261 people since December, nearly all in the southeast of the country. Millions of Brazilians have been vaccinated as authorities scramble to prevent the outbreak from turning into an epidemic.
Scientists do not know why yellow fever is rebounding in a country that had all but eradicated the illness, especially in big cities. Yellow fever, one of the deadliest tropical diseases, causes muscle aches and fever and can lead to complications like jaundice and kidney failure.
The World Health Organization recommended in March that travelers to rural areas in the states of Rio de Janeiro and Sao Paulo get yellow fever vaccinations.
The outbreak has so far been limited to “rural” yellow fever, which is cases of the virus spread by mosquito species not common in urban areas. It has infected some humans, but mostly monkeys.
Yellow fever is found in tropical parts of Africa and the Americas and is transmitted by the same type of mosquito that spreads dengue and the Zika virus.
The mosquitoes feed on primates. The first sign that the disease was back in Brazil was the discovery of hundreds of dead monkeys in the Atlantic rainforest, where it has threatened the survival of rare South American primates.
Yellow fever originated in Africa, where it is still a major killer, and spread to the Americas on slave ships.