As Brazil continues to fight the yellow fever epidemic that started last year, the WHO recommended on Monday that travelers going to rural areas in Rio de Janeiro and Sao Paulo get vaccinated against yellow fever.
There are 137 reported deaths due to yellow fever in Brazil since December. Most of these cases have been limited to rural areas, because they have been transmitted by rural mosquitoes. It is critically important to continue monitoring this disease, both to understand why the incidence has suddenly spiked in rural areas, as well as to watch out for spread to urban areas. If the city-dwelling mosquito species Aedes aegypti starts spreading yellow fever, the outbreak could increase exponentially, as the mosquito could infect many more people in dense city neighborhoods. These investigations have already begun, as health officials have started to examine monkeys who have been found dead within the city limits of Rio. If these monkeys are seropositive for yellow fever antibodies, then there would be reason to believe that the virus has started to spread in the city.
Prada P. Yellow fever vaccine advised for travel to Brazil's Rio, Sao Paulo states. Reuters: 20 March 2017. http://www.reuters.com/article/us-brazil-health-yellowfever-idUSKBN16R2C8