The European Centre for Disease Prevention and Control (ECDC), in an epidemiologic update yesterday on Brazil, noted one additional suspected yellow fever case in Rio de Janeiro state. Late last week, the Brazilian ministry of health confirmed two cases of the mosquito-borne disease in that part of Brazil, including one death.
Though only three cases have been reported in Rio de Janeiro state, the nation is on high alert for signs that the disease may be traveling toward Rio de Janeiro, the state’s capital and most populous city. Most people in Rio are unvaccinated against yellow fever, and the city harbors Aedes aegypti mosquitoes, which can transmit the disease.
"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," the ECDC said in its assessment.
Brazil's outbreak remains largely contained to the states of Minas Gerais, where there are 1,074 cases and 189 deaths; Espirito Santo, with 243 cases and 48 deaths; and Sao Paulo, with 15 cases and 4 deaths. Four other states — Bahia, Tocantins, Rio Grande do Norte, and Goias — have reported a handful of suspected cases, but none have been confirmed.
CDC updates travel information
On Mar 20, the World Health Organization updated its vaccination recommendations to travelers going to Brazil, adding Rio de Janeiro and Sao Paulo states to the sites where yellow fever vaccination is recommended. The major cities of Rio, Niteroi, Sao Paulo City, and Campinas are excluded from the recommendation.
In light of this change, the US Centers for Disease Control and Prevention (CDC) issued new travel guidance on the country yesterday, placing travel to Brazil at the "alert" level, which means "practice enhanced precautions." That's the CDC's second of the three levels, between "watch" and "warning."
"Anyone 9 months or older who travels to these areas should be vaccinated against yellow fever. People who have never been vaccinated against yellow fever should not travel to areas with ongoing outbreaks," the CDC said. The agency also recommended a booster shot to travelers going to the area who had been vaccinated more than 10 years ago.
Monkey population decimated by outbreak
Brazil's current outbreak began in the country's jungles, where a sylvatic (jungle) strain of the disease circulated among non-human primates late last year. A University of Wisconsin-Madison anthropologist who has studied these jungles for more than 30 years said the current outbreak has killed thousands of monkeys.
Most of the monkeys that have perished from yellow fever are brown howlers. This createw an interesting opportunity for the critically endangered muriqui monkeys, according to a UW-Madison news release. Muriquis, or woolly spider monkeys, are less susceptible to yellow fever. Researchers are studying if their population will thrive in the absence of howlers.
"No one really knows the consequences for the other primates or the forest when nearly the entire population of an abundant species dies from disease in just a few months," says Karen Strier, PhD, professor of anthropology. "We are in a position to learn things we never knew before, with all the background information that we have collected."
Mar 22 ECDC epidemiologic update
Mar 22 CDC travel update
Mar 21 UW-Madison press release