Ask the doctors: West Nile Virus most common mosquito-borne disease

Dear Doctors: Our local news is full of stories about West Nile virus. Apparently we’re seeing cases here in Tennessee, and also in states around us. Some people are getting really sick. What are the symptoms of West Nile virus? Is there a treatment? What about a vaccine?

Dear Reader: Warmer weather ushers in some of the worst aspects of summer – mosquitoes. And, thanks to global rising temperatures, this year it arrived earlier than usual. The varied habitats throughout the U.S. are home to more than 200 different species of mosquitoes. About 12 of them are known to carry viruses that can cause disease. West Nile virus, which first emerged in the United States in 1999, is now the most common. Last year, more than 2,500 cases of the virus were reported throughout the lower 48 states. So far this year, 11 states have reported 15 verified cases of the infection. Half progressed to serious disease that required hospitalization.

Mosquitoes can pick up a virus if they feed on an infected animal, bird, reptile or human. The virus then multiplies inside of the mosquito. When the insect has its next blood meal, the virus it carries can be transmitted via its saliva. It does not move from person to person.

It can take anywhere from three days to two weeks after being bitten for symptoms to appear. However, the majority of people infected with the virus – the estimate is 80% – have no symptoms. When illness does occur, it is typically mild to moderate. Symptoms include fever, muscle and body aches, intense headache, swollen lymph nodes and nausea. Some people can develop a rash, joint stiffness or pain and experience fatigue that can persist for several weeks. A fraction of those who become infected with the virus – about 1 in every 150 – develop potentially serious illnesses. These include meningitis, which is inflammation of the membranes that surround the spinal cord and the brain, and encephalitis, which is inflammation of the tissues of the brain.

Symptoms of severe illness include high fever, headache, stiff neck, sensitivity to sound or light, muscle weakness, tremor, changes to behavior or cognition, numbness, seizures and paralysis. These symptoms can begin as mild and intensify over the course of a few days, or even a few hours. Meningitis and encephalitis are potentially fatal, and immediate medical care is needed. Older adults and those with weakened immune systems are at higher risk of more serious illness.

There is no specific medication or treatment for West Nile virus. Mild to moderate symptoms can be managed with the same types of medications used for cold and flu.

In severe disease, hospitalization becomes necessary. Treatments include the use of supplemental oxygen, corticosteroids to manage inflammation, IV fluids for hydration and antiseizure medications if needed. Although vaccines are available for horses, at this time there are no vaccines that have been approved for human use.

Send your questions to askthedoctors@mednet.ucla.edu.