Brazil yellow fever outbreak could spread to US

Yellow fever could become the fifth mosquito-borne virus to hit the US in recent years, experts from the National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda, Maryland warned.

In an on-going outbreak in rural Brazil though there had been no human-to-human transmission through Aedes aegypti mosquitoes, the infection had spread via non-human forest-dwelling primates, write Infectious Disease Fellow Catharine I Paules, MD, and NIAID Director Anthony S Fauci, MD, in an article published online yesterday in the New England Journal of Medicine.

But there were concerns that human-to-human transmission might occur as the outbreak was in the vicinity of major urban areas, where yellow fever vaccine was not routinely administered.

The outbreak in the Brazilian states of Minas Gerais, Espirito Santo, and São Paulo had taken a toll of 80 lives with 234 confirmed infections as of February 2017. "The high number of cases is out of proportion to the number reported in a typical year in these areas," write Dr Paules and Dr Fauci.

They further noted that, as with Zika, arbovirus epidemics spread by A Aegypti could move rapidly through populations that lacked immunity and could be readily spread by human travelers.

The warmer regions of the continental US were vulnerable to yellow fever outbreaks.

According to experts, the looming danger of a spreading outbreak was made worse by the fact that, while an effective vaccine against yellow fever had been around since 1937, worldwide stockpiles had been running dangerously low.

In outbreaks of the disease two years back in Angola and Democratic Republic of Congo, public health officials ran so short of the vaccine that they resorted to giving each person one-fifth of a dose.

According to Fauci, only a few companies worldwide manufactured the vaccine, and making additional doses took time.