West Nile Virus in Philadelphia: What to know about the mosquito-borne illness

Three people in Philadelphia have been diagnosed with severe West Nile virus with neurological complications as of last week.

Most people who are bit by an infected mosquito don’t get sick or experience any symptoms, but in rare instances, the virus can cause severe illness that affects the central nervous system.

The virus has been detected in mosquitos in Philadelphia and all of its surrounding Pennsylvania counties, as well as much of the state.

» READ MORE: Two Philadelphians have been diagnosed with West Nile virus, health department says

Philadelphia routinely tests mosquito pools and has found a higher positivity rate this year compared to years past. That means an increased risk of contracting West Nile.

Mosquitos are most active between May and October, but mosquito-borne illness remains a risk until the first frost.

Here’s what you need to know about West Nile virus to protect yourself and your loved ones:

West Nile virus is a common mosquito-borne illness. It is spread when infected mosquitos bite people. There is no vaccine.

Most people who are infected don’t get sick and don’t experience any symptoms. About 20% of people develop a fever, according to the Centers for Disease Control and Prevention. Other symptoms can include headache, fatigue, joint pain, body aches, vomiting, diarrhea, and rash.

Serious illness from West Nile virus is rare. About 1 in every 150 people infected develop severe symptoms that affect the central nervous system, such as brain and spinal cord inflammation, according to the CDC.

About one in 10 people who develop severe illness affecting their central nervous system die. Most recover from severe illness in several months, though they may experience permanent effects.

Symptoms of severe illness from West Nile include high fever, headache, stiff neck, disorientation, tremors, muscle weakness, vision loss, and numbness.

People over age 60 are at greater risk for severe illness.

Kids experience similar symptoms to adults, and most do not get sick from West Nile virus.

Apply insect repellent to children by spraying it into your hands, then rubbing on their skin. Avoid their mouth, eyes, hands, and any cuts.

The Environmental Protection Agency’s online search tool can help identify the best repellent for your family and offers guidance on how often to reapply.

» READ MORE: Avoiding summer bites: A look at West Nile virus and Lyme disease in the Philly area

Dogs and cats can contract West Nile virus but it’s unlikely, according to UC Davis Veterinary Medicine. Symptoms may include fever, muscle spasms, and weakness, and must be diagnosed by a veterinarian.

Do not apply human insect repellent to pets, as it can be poisonous to animals.

People who are pregnant are not at higher risk of illness from West Nile virus. It is possible for an infected person to pass on the virus to their baby, but highly unlikely. Only a few cases of a newborn with West Nile virus have been documented, according to the CDC.

Wear loose-fitting, long-sleeve shirts and pants when possible, and use insect repellent to protect against mosquito bites during pregnancy.

Philadelphia and the surrounding counties are routinely monitoring for West Nile virus and spraying to control mosquito populations. Check with your county’s health department for more information about when spraying may be scheduled for your neighborhood.