Scientists Fear Yellow Fever May Soon Return to Southeastern U.S.

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Oct. 19, 2023 – Medical experts are worried that yellow fever and its feared “black vomit” may re-emerge in the American South in the near future.

The viral illness is transmitted by mosquitoes and rampaged throughout the South and Mississippi Valley for nearly 100 years starting from 1820 to 1905. In 1853, a yellow fever epidemic killed 11,000 people in New Orleans, which at the time was about 10% of the city’s population. 

“We’ve seen a rise in mosquito-transmitted illnesses in Texas and Florida, including malaria, dengue, chikungunya and Zika virus, but now we’re also worried about yellow fever since it seems to be accelerating in tropical regions of Latin America such as Brazil and Venezuela,” Peter J. Hotez, MD, PhD, dean of the National School of Tropical Medicine at Baylor College of Medicine, said in a statement. “The consequences of a high mortality infection like yellow fever re-emerging in the southern U.S. would be profoundly destabilizing.”

Hotez and fellow researcher Angelle Desiree LaBeaud, MD, of Stanford University, reported the prediction for yellow fever’s re-emergence in Thursday’s edition of TheNew England Journal of Medicine.

The combination of global warming, urbanization, and “shifting patterns of human migration” are driving predictions that show infections and viruses transmitted by mosquitoes will rise dramatically in the coming years, Hotez and LaBeaud wrote. The threat is greatest in southeastern parts of the U.S., stemming from “extreme poverty throughout Texas and the Gulf Coast states, where inadequate or low-quality housing, absent or broken window screens, and a pervasive dumping of tires in poor neighborhoods” that create prime breeding grounds for mosquitoes, they explained.

After the virus is transmitted from the bite of a mosquito, symptoms may appear in 3 to 6 days, although not everyone has symptoms. Common symptoms are fever, muscle pain, headache, loss of appetite, and vomiting, all of which usually let up in 3 to 4 days, according to the World Health Organization. But “a small percentage” of people then move to a toxic second phase within a day of apparent recovery, and they can have a high fever and an assault on the liver and kidney systems. Black vomit can occur in the end stages due to bleeding in the gut.

“In this phase, people are likely to develop jaundice (yellowing of the skin and eyes, hence the name yellow fever), dark urine, and abdominal pain with vomiting,” the WHO explains. “Bleeding can occur from the mouth, nose, eyes, or stomach. Half of the patients who enter the toxic phase die within 7-10 days.”

Yellow fever can be prevented by a safe and affordable vaccine, according to the WHO. A single dose provides lifelong protection. Yellow fever is currently thriving in 13 Central and South American countries and in 34 African countries, where the disease is considered endemic. 

“The mosquitoes that spread yellow fever are here in the U.S. and conditions are increasingly favorable for them as our world warms,” LaBeaud, a professor of pediatrics-infectious disease at Stanford Medicine, said in the statement. “We need a comprehensive plan to better protect at-risk communities in the southern U.S. from mosquito-borne diseases.”