Keystone Virus: The New Mosquito Virus

What is the deadliest animal to mankind? A snake, lion, grizzly bear, or perhaps a hippopotamus? While these creatures are dangerous, the deadliest animal on the planet is actually the mosquito.

The World Health Organization (WHO) estimates that, worldwide, mosquito bites kill one million people annually. Mosquitoes spread many diseases including malaria, Dengue, Zika, Chikungunya, encephalitis, and elephantiasis. While doctors and researchers work to combat well-known diseases caused by mosquito bites, a new mosquito-borne disease has surfaced.

Researchers at the University of Florida diagnosed Keystone virus in a 16-year old boy, the first confirmed human case. The teen reported being bitten multiple times by mosquitoes in August of 2016, while attending a band camp in North Central Florida.

The researchers tested the patient’s saliva and urine for the more common mosquito-borne diseases Zika, Dengue, and Chikungunya. All three tests were negative. This was especially puzzling because Florida was experiencing a Zika outbreak at the time. Despite lacking a dedicated test for Keystone virus, the researchers then analyzed additional saliva and urine samples. They identified the virus by comparing their findings with known viral genomes.

About the Virus

Until this discovery, the virus had only been identified in non-human animals, including squirrels, whitetail deer, and raccoons. First discovered in 1964 in mosquitoes in Keystone, Florida, it was later detected in mammals in coastal habitats from Texas to the Chesapeake Bay. It belongs to a class of viruses called orthobunyaviruses. Specifically, it is part of the California group of orthobunyaviruses, which attack the nervous system, particularly the central nervous system (CNS).

The virus is spread by Aedes atlanticus, a mosquito species common in Florida. This species is closely related to Aedes aegypti, a vector of Dengue, Zika, Chikungunya, and yellow fever.

Although this is the first identified human case, it may not be the first human infection.

Humans have been exposed to this virus for decades, but without a specific test for it, doctors couldn’t assign any illnesses to it.

Researchers have long speculated that Keystone virus infected humans. Some blood samples from Tampa Bay residents collected in the 1970s had antibodies against Keystone virus. This new revelation confirms decades of suspicions.

Symptoms and Treatment

Given the lack of confirmed cases, there are no symptoms specifically attributed to Keystone virus infection. 

However, the Florida teenager had the following symptoms:

  • Low-grade fever
  • A red rash (that did not itch) that spread from his chest to his abdomen, back, limbs, and face 
  • Mild fatigue

He showed no neurological symptoms, despite the propensity for orthobunyaviruses to affect the CNS.

Why it Should Concern You

Recent years have seen a rise in epidemics of mosquito-borne diseases, including West Nile virus, Zika, Chikungunya, and Dengue. This indicates increased prevalence of bites and/or infected mosquitoes, making Keystone virus infection a concern as well. Mosquitoes, albeit seasonal in many areas, are found in most of the world. The chance of becoming infected by one of the diseases they carry is often present.

Some of the California group orthobunyaviruses are known to cause brain inflammation. It is unclear if the Keystone virus has this same effect. Given its classification in the California group, however, it certainly could. 

Can’t Fight the Virus, Fight the Bite

Because the condition caused by the Keystone virus is relatively unknown, there is no recommended treatment. The best way to fight the virus is to avoid mosquito bites. This has the added benefit of protecting you against better known mosquito-borne illnesses as well.

Mosquitoes reproduce rapidly, which contributes to increases in disease prevalence. This means that control methods also need to act rapidly.

There are multiple approaches to control mosquitoes. The most effective methods focus on preventing breeding.

Mosquitoes lay their eggs in standing water. Be sure to dump all standing water around your home. Regularly change the water in bird baths, potted plants, and wading pools.

Mow your lawn and trim back bushes. When you plan to spend time outdoors, use a mosquito fogger to prepare the area. It only controls mosquitoes for a couple hours and poses a threat to beneficial insects. Therefore, only use it as a temporary control for planned outdoor gatherings.

Wear insect repellent, long sleeves, and long pants when you are outdoors. To keep mosquitoes out of the house, install screens with a small mesh in vents and windows. If you are in an area with high mosquito prevalence without a way to keep them out, sleep under treated mosquito nets.

Parting Shot

Mosquitoes carry many dangerous diseases, some of which are lethal. Researchers may add the Keystone virus to that list in the near future as diagnostic testing becomes available and we learn more about its effects. It’s important to take steps to protect yourself from mosquito bites. Remember, despite how scary other species may appear, the mosquito is considered the deadliest animal on Earth. 

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