USA officials keep watchful eye on yellow fever outbreak in Brazil

Danger A regional outbreak of yellow fever has manifested in rural Brazil and could affect millions if it reaches densely-populated cities such as Rio de Janeiro and Sao Paulo

What started in December as a rural, sylviatic (jungle-related) yellow fever outbreak in Brazil is now pushing toward urban areas, which could pose a risk of worldwide spread to U.S. states and territories, similar to what happened with Zika virus, federal infectious disease experts warned yesterday.

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, they added, "it is possible that travel-related cases of yellow fever could occur, with brief periods of local transmission in warmer regions such as the Gulf Coast states, where A. aegypti mosquitoes are prevalent".

Experts fear spread of the disease may resemble that of the Zika virus, which emerged in Brazil in 2015 and later spread to more than 60 countries including the USA, causing local outbreaks in Florida.

Over the past few weeks, the Latin American country has seen an uptick in yellow fever cases in some of its rural areas. But the World Health Organization expanded its vaccination recommendation to include parts of the state in January. With the recent outbreak, Brazilians health workers are now urging people to get vaccinated right away.

Although there is a vaccine for yellow fever it is not given as a routine vaccination program in Brazil, the Pittsburgh Post-Gazette reported. The Pan American Health Organization said that as of March 2, the virus has killed about 220 people mainly in the states of São Paulo, Minas Gerais, and Espírito Santo. But he would worry, he added, if cases of yellow fever begin to turn up in such cities as Sao Paolo, Rio de Janeiro or Brazilia among people who have not come in from the jungles.

During the 2015 outbreak in Angola and Congo, health officials were constrained to administer to each infected person only a fifth of the normal dose.

Yellow fever has a relatively high death rate and "is the most severe [insect-transmitted] virus ever to circulate in the Americas", Fauci and Paules wrote.

That mosquito, common in many tropical and subtropical cities, also carries the dengue and Zika viruses, which has been linked to thousands of babies being born with underdeveloped brains.

The United States also had the worst Zika outbreak with Florida being the most affected.

Among the five, the yellow fever is considered the most deadly, Fauci and Paules said. Extensive immunization campaigns, along with effective mosquito control - especially in developed countries - have reduced yellow fever cases worldwide.

"As with all potentially reemerging infectious diseases, public health awareness and preparedness are essential to prevent a resurgence of this historical threat", they write. CDC reiterated the importance of quickly detecting and controlling outbreaks to reduce the illness, death and prevent the spread of the disease to other regions.

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