Brain Swelling-Causing Mosquitoes Detected In Florida

Photo by Robina Weermeijer on Unsplash

Florida health officials are warning about a detected deadly mosquito-borne virus known as Eastern equine encephalitis (EEE) that causes brain swelling in humans.

Several sentinel chickens tested positive for carrying the Eastern equine encephalitis virus or EEEV, which may quickly find its way to infecting humans.

Sentinel chickens are fowl that are tested regularly for the West Nile virus and EEE. Their blood can show the presence of the diseases, but they don’t suffer from the effects of the infections.

Following the positive tests of sentinel chickens in Orange County, the health department announced that the risk of virus transmission to humans has increased.

In particular, EEEV is transmitted to humans through the bite of an infected mosquito. However, the virus can only be maintained in a cycle between the Culiseta melanura mosquito and its victim. In most cases, the Culiseta melanura mosquito does not feed on humans and prefers almost exclusively on birds.

In other words, transmission to humans requires mosquito species capable of creating a “bridge” between infected birds and uninfected mammals. Consequently, the discovery of sentinel chickens positive with EEEV in Florida is a clear sign that the virus is now openly transmittable to humans.

Fortunately, only about seven cases of the EEE virus in humans are reported in the US each year, the Centers for Disease Control and Prevention says.

Furthermore, human EEEV cases occur relatively infrequently, largely because the primary transmission cycle takes place in and around swampy areas — where human populations tend to be limited.

Overall, only about 4-5% of human EEEV infections result in death-causing EEE. There are also non-conclusive studies stating that experiencing EEEV infection can result in life-long immunity against re-infection.

However, the disease can be fatal: about 30% of people who contract the virus die.

Death usually occurs 2 to 10 days after onset of the symptoms but can occur much later. Of those who recover, many are left with disabling and progressive mental and physical sequelae, which can range from minimal brain dysfunction to severe intellectual impairment, personality disorders, seizures, paralysis, and cranial nerve dysfunction. Many patients with severe sequelae die within a few years.

As a precaution, all residents of and visitors to areas where EEEV activity has been identified are at risk of infection. The same precautions are also adviced for people who engage in outdoor work and recreational activities in endemic areas are at increased risk of infection.

Specifically, the CDC warns that persons over the age of 50 and under the age of 15 are more likely to be at greatest risk for developing severe disease when infected with EEEV.

People can tell if they are infected with the virus through a set of symptoms that manifest after transmission. The incubation period for the EEEV disease (the time from an infected mosquito bite to onset of illness) ranges from 4 to 10 days. EEEV infection can result in one of two types of illness, systemic or encephalitic.

Particularly EEE with systematic illness can start by characterizing itself through chills, fever, malaise, arthralgia, and myalgia. The illness lasts 1 to 2 weeks, and recovery is complete when there is no central nervous system involvement.

For infants, the encephalitic form (involves swelling of the brain) is characterized by abrupt onset; in older children and adults, encephalitis is manifested after a few days of systemic illness.

Signs and symptoms in encephalitic patients are fever, headache, irritability, restlessness, drowsiness, anorexia, vomiting, diarrhea, cyanosis, convulsions, and coma.

Furthermore, the type of illness will depend on the age of the person and other host factors. It is possible that some people who become infected with EEEV may be asymptomatic (will not develop any symptoms).

As a prevention measure, The Florida Department of Health in Orange County (DOH-Orange) says that it is best to practice DRAIN and COVER.

Drain meaning that residents should al practice draining all possible locations for mosquitoes to lay their eggs on. This can come in the form of stagnant water sitting on unused pots and pans, garbage cans, house gutters, buckets, pool covers, coolers, toys, flower pots or any other containers where sprinkler or rainwater has collected.

Secondly, cover means simply shielding yourself from possible mosquito bites. This can be in the way for you to cover your skin with clothing or repellant, and using screens to cover doors and windows.

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