West Nile Virus & Mosquitoes

Author: Mosquito Squad of Greater Washington DC

West Nile virus is a viral infection transmitted to humans by mosquitoes. The virus is widely spread across the world with cases having been documented in Europe, the Middle East, Africa, India, Asia, America, Canada, and Australia. Most people infected with the virus will be unaware, with four out of five people having no signs or symptoms at all.

The Transmission of West Nile Virus & Mosquitoes

The West Nile virus transmission cycle occurs between mosquitoes and birds before infecting humans, horses and other mammals. It primarily involves the common house mosquito, otherwise known as the Culex species, when they feed on the blood of infected birds. It takes between ten days to two weeks for the virus to enter the mosquito’s salivary glands where it then can be transmitted through a mosquito bite. There are at least 17 known bird species that have tested positive to the virus. However, as the mosquito can transmit the virus to other birds in an escalating cycle, this number could increase.

It is not possible for the virus to be spread from one person to another; a mosquito must bite you to pass on the infection. But it only takes one bite! Although extremely rare, the West Nile virus has been transmitted through blood transfusions and organ transplants. There have been a very small number of cases where the virus has been transmitted from a mother to fetus during pregnancy, labor or through breastfeeding the infant. Generally speaking, the infection is linked directly between the West Nile Virus and Mosquitoes.

What Are the Symptoms of the West Nile Virus?


Of those who have been infected with the West Nile Virus by a mosquito most will not develop any sign or symptoms. Approximately 20% of people infected with West Nile virus experience mild flu-like symptoms including:

  • A headache
  • Fatigue
  • Fever
  • Aching muscles or joints

Although rare, some people have shown signs of skin rash, swollen lymph glands, and eye pain. Most people presenting with these symptoms will recover completely within a couple of weeks. However, fatigue can in some cases drag out for months.

Less than 1% of people infected with the West Nile Virus present with serious symptoms developing into serious neurologic illness such as encephalitis or meningitis. Symptoms of a neurologic disease including:

  • A headache
  • Fever
  • Neck stiffness
  • Disorientation
  • Coma
  • Tremors
  • Seizures
  • Paralysis

This occurs as the virus enters the brain or into the tissues of the brain or spinal cord. It is a serious disease and can leave people with long-term side effects or disability and about 10% of those who get West Nile encephalitis or meningitis will die.

People with existing medical conditions such as cancer, diabetes or kidney disease are at greater risk for serious illness resulting from the West Nile Virus.

What Is the Treatment of West Nile Virus If I Get Infected?


There are no medications to treat the illness if you get infected. Common pain medications can assist in relieving the mild flu-like symptoms, although most recover on their own.

In more severe cases, the patient may require hospitalization. In this case, they will often be given intravenous fluids, strong pain medication and provided with supportive nursing care.

Currently, there are no vaccinations to protect and prevent the spread of the West Nile Virus from mosquitoes.

What Is the Difference Between the West Nile Virus and Malaria?


Malaria is probably one of the most well-known diseases caused by mosquitoes. Although both the West Nile Virus and Malaria are transmitted through the insect's bite, there are several differences including:

  • Malaria is a parasite whereas the West Nile is a virus.
  • Malaria kills over 80% of people who have been infected. Less than 1% of people who are infected with the West Nile virus develop a serious illness.
  • West Nile virus does not always present with symptoms whereas the symptoms of Malaria evident immediately.

There are, however, some similarities other than the source. Currently, there are no vaccines available to prevent the spread of Malaria or the West Nile virus and both are potentially life-threatening.

You can reduce your chances of being infected by the West Nile virus by avoiding mosquito bites. Ensure you use repellents containing EPA-registered active ingredients such as DEET when outdoors. Avoid mosquito-prone areas and wear appropriate loose-fitting clothing to cover any exposed skin.