West Nile virus season is back – a medical epidemiologist explains how the virus is transmitted and the right way to avoid it

The West Nile virus is essentially the most common mosquito-borne disease within the continental USA, with a median of two,464 reported cases per yr.

Every August, the West Nile season reaches its peak, especially in parts of the South and West of the United States.

The Conversation US asked neurologists and medical epidemiologists Daniel Pastula to clarify what researchers find out about West Nile virus and the way you possibly can protect yourself from contracting the disease.

What is West Nile virus?

West Nile is a virus that first identified within the West Nile region of Uganda in 1937 and subsequently caused outbreaks throughout Africa, the Mediterranean, and parts of Europe.

It got here to the New York City area in late 1999probably from an infected bird or mosquito. The virus has since spread throughout the American continent and other parts of North America and has develop into endemic.

How is West Nile virus transmitted?

The West Nile virus is transmitted to humans mainly through mosquito bites. exists in a transmission cycle between different birds resembling crows, robins and blue jays and particularly several Culex Types of mosquitoesthat are quite common within the USA

The mosquitoes develop into infected by feeding on infected birds which have high levels of the virus. The infected mosquitoes then transmit the virus to other birds by feeding on them.

Sometimes an infected mosquito bites a human, horse or other mammal and transmits the virus to them. However, the extent of virus in these animals' blood doesn’t develop high enough to sustain the cycle. In other words, they’re “dead-end hosts.”

In rare cases, the West Nile virus transferred in another wayincluding accidental laboratory exposure, blood transfusion or organ transplantation. In very rare cases, it could actually be transmitted while pregnant, childbirth or breastfeeding.

When and where does it appear and is it seasonal?

In the continental United States, most cases of West Nile virus disease in humans occur in July to Septemberor until the primary heavy frost or snowfall. This is often known as the “West Nile season.” By this time of yr, mosquitoes have had loads of time to emerge, feed on infected birds, and develop into infected themselves.

In more southern areas resembling Arizona, Florida and Texas, transmission by mosquitoes can occur before July and after September. For example, mosquitoes infected with the West Nile virus in Texas already reported in May 2024.

While cases of West Nile virus disease in humans have been reported within the 48 continental states, the District of Columbia and Puerto RicoThe majority of cases within the last 20 years concerned the Great Plains, South and Southwest USAThis might be related to the mosquito species, birds, bird migration patterns, temperatures, rainfall and irrigation practices in these areas.

How dangerous is the West Nile virus?

Approximately 80% of individuals infected with West Nile virus haven’t any or only very mild symptoms.

But about 20% of the timeWhen infected with the West Nile virus, people may experience a sudden flu-like illness with symptoms resembling high fever, headache, muscle and joint pain, stomach problems resembling nausea, vomiting and diarrhea, rash and fatigue inside two to 14 days of being bitten by a mosquito that transmits the West Nile virus.

Most people get well from this “West Nile fever”, However, the fatigue can last for weeks or months..

In about 1% of cases, nonetheless, the virus can penetrate the meninges and cause a so-called meningitis; the brain itself, which results in Encephalitis; or the spinal cord, which results in Polio-like syndromeWhen the virus enters the nervous system in this manner, it is named “West Nile syndrome, neuroinvasive disease.”

About 10% of cases of neuroinvasive West Nile disease are fatal, especially in cases where the brain and spinal cord are directly infected. Many survivors have everlasting neurological disability resembling weakness, movement disorders or cognitive problems to various degrees.

The risk of neuroinvasive West Nile disease is higher in people aged 60 years or older, in individuals with weakened immune systems, and in individuals with medical conditions resembling cancer, diabetes, or kidney failure.

Are there any treatments or vaccines?

While A wide range of treatments have been investigatedThere are currently no proven antiviral treatments for West Nile virus disease. Treatment stays largely focused on controlling symptoms.

Some patients may have over-the-counter medicines for fever and headache, fluids for dehydration, medicines for nausea or vomiting, and rest. Some patients may have to be hospitalized and treated for severe dehydration, organ dysfunction, seizures, or brain swelling.

However, there are currently no West Nile vaccines approved to be used in humans. Some vaccine candidates and concepts are being investigated.

How are you able to help prevent this?

In general, in case you prevent mosquito bites, you furthermore mght prevent infection with the West Nile virus. There are several things you possibly can do to Prevent mosquito bites:

First, use a Environmental Protection Agency registered insect repellent on exposed skin when you find yourself outside in an area with mosquitoes. These are protected and effective when used as directed.

You can even wear long-sleeved shirts and pants if possible. It is far more difficult – and even unimaginable, depending on the material – for mosquitoes to bite through clothing. You can even Treat your clothes with permethrinan insecticide that moreover repels mosquitoes.

If possible, avoid being outdoors between dusk and dawn. This is when West Nile mosquitoes are most lively.

It's also an excellent idea to remove any unnecessary standing water in places like birdbaths or wading pools in your property, as mosquitoes wish to breed in standing water. Indoors, be sure that all windows without screens are closed to maintain mosquitoes out. These easy precautions can greatly reduce the danger of great illness.

In addition to those individual precautions, comprehensive public health and vector control programs help monitor and control the spread of West Nile virus by alerting residents of affected areas to the presence of the virus and reducing the population of infected mosquitoes when vital.