In 2019, there was a marked rise in cases of Eastern equine encephalitis (EEE) in both horses and humans. Last year, human cases of EEE were five times higher than average, with the most cases occurring in Florida, Massachusetts, Michigan, New York and North Carolina during August and September. It's not clear what caused the spike in cases or if the rise will continue in future years.
EEE is endemic in North America and is transmitted in freshwater swamps. Commonly found in the Atlantic and Gulf Coast states, as well as the Great Lakes region, the virus is spread between birds and mosquitoes, with mosquitoes transmitting the disease to human and equine hosts. Both horses and humans are dead-end hosts for EEE because the concentration of the virus in blood is too low to infect biting mosquitoes.
Horses can be vaccinated for EEE, which is an effective way to stop the spread of the disease that kills 90 percent of infected horses. The virus can also infect alpacas, dogs, cats, cattle, deer, llamas, goats and pigs. There is no human vaccination.
There are many factors that affected the number of EEE cases in 2019, including high rainfall, which created breeding grounds of mosquitoes; warmer temperatures, which increased the rate at which the mosquito larvae grew; and high humidity and temperature combined, which allowed mosquitoes to live longer.
People infected with EEE may have chills, fever and muscle and joint pain; only four to five percent of humans with EEE get encephalitis. Of those, up to 40 percent may die. Confirmation of EEE in humans is made from blood or spinal fluid tests. Treatment for EEE in humans is supportive. It is recommended that people cover bare skin and use mosquito repellents when outdoors during mosquito season.
The number of cases of EEE in the United States in 2020 and beyond is uncertain, but it will not disappear from endemic areas. Preventative measure for both humans and horses should be taken.
Read more at Helio Infections Disease News.
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