Protecting yourself from mosquito-borne illnesses

Hiker spraying herself for mosquitoes

With all the rain that has fallen on New England and the Monadnock Region this summer, the mosquito population is likely on the rise. The increased amount of standing water, changing weather patterns, and a rise in temperature and humidity will likely lead to a surge in mosquitos.

More than 200 types of mosquitoes live in the United States and U.S. territories, and of those, 12 types can carry mosquito-borne illnesses, according to the Centers for Disease Control (CDC). We asked Aalok Khole, MD, infectious disease physician at Cheshire Medical Center and Elizabeth A. Talbot, MD, from Dartmouth Health's Infectious Disease and International Health, what we need to know about mosquito-borne illnesses and how to protect yourself and your family.

“One thing to know is that it is not only travel-associated,” Khole said. “Certain mosquito-borne illnesses can be acquired locally. Most importantly, they are preventable.”

What is a mosquito-borne illness?

Mosquito-borne illnesses are diseases humans can get from the bite of an infected mosquito. Each year, mosquito-borne illnesses infect about 700 million people worldwide and kill about 1 million. A lot of these diseases are tropical, such as Yellow Fever, West Nile Virus, Dengue, Zika, or malaria.

Are there mosquito-borne illnesses in our area?

Unfortunately, yes. Mosquito-borne diseases transmitted in New Hampshire and Vermont include West Nile virus, Eastern Equine Encephalitis virus, and Jamestown Canyon virus. All 3 of these mosquito-borne illnesses are relatively rare in New Hampshire and Vermont, but that doesn’t mean we shouldn’t be cautious.

The occurrence of these infections is highly regional, with differences even between New Hampshire and Vermont, including whether or not the disease has been found in humans or detected in tested mosquitos. Surveillance for these diseases in animals and mosquitos is not conducted systematically in all settings, so even if not identified in your neighborhood, you may still be at risk.

What are the symptoms?

A person with any of these three diseases can experience a range of symptoms—from no symptoms (asymptomatic) to having fever, chills, headache, rash, bruising easily, fatigue, and muscle aches to even having a severe neurological (nervous system) disease or systemic organ failure.

An estimated 80% of human West Nile virus infections don’t require medical care. Symptoms of more severe illness from West Nile virus could include high fever, headache, neck stiffness and disorientation, with a small percentage—maybe 1%—of those infected developing a severe neurological infection like meningitis—an inflammation of the fluid and membranes surrounding your brain and spinal cord, encephalitis—inflammation of the brain, or acute flaccid paralysis, an uncommon, but serious condition that causes muscle paralysis.

Eastern Equine Encephalitis tends to cause more severe disease. Approximately one-third of individuals who develop illness may develop severe encephalitis. Symptoms from this virus may include vomiting, diarrhea, seizures, behavioral changes or coma.

Although it may be that asymptomatic or mild cases do not come to medical attention, early estimates are that about half of known Jamestown Canyon virus patients end up in the hospital. Serious symptoms of this virus include stiff neck, confusion, loss of coordination, difficulty speaking or seizures.

The incubation period for these diseases—meaning the time it takes to get sick after the initial bite—is 1 to 2 weeks; malaria may be longer.

Seek medical attention if you notice any of the above severe symptoms.

“Please remember that all mosquitos aren’t harmful, and all bites aren’t infective,” Khole said. If infected, most individuals can remain asymptomatic or have mild disease; severe disease is uncommon.

When should I get medical care?

Contact your primary care provider or walk in for an Urgent Visit if you experience mild symptoms that could be a mosquito-borne illness or other virus:

  • Bruising easily
  • Diarrhea
  • Fever
  • Headache with other symptoms
  • Neck stiffness with other symptoms
  • Vomiting

Call 9-1-1 or visit Cheshire’s Emergency Department if you have the following severe symptoms:

  • Behavioral changes, along with other symptoms
  • Confusion or disorientation
  • Difficulty speaking
  • Loss of coordination
  • Paralysis
  • Seizures
  • Unconsciousness

How can I protect myself and my family?

The greatest risk for mosquito-borne infection due to West Nile virus and Eastern Equine Encephalitis is between July and October, while the risk for Jamestown Canyon virus can be present as soon as the snow melts. The risk for these diseases decreases in the fall after the daylight hours shorten and the first hard frosts kill active mosquitoes.

Here’s how you can protect yourself and enjoy the outdoors:

  • Adults should wear an Environmental Protection Agency (EPA)-registered insect repellent containing at least 30% DEET. Picaridin and oil of lemon eucalyptus are also effective. The CDC website lists others. Follow manufacturer instructions for applying insect repellent on children. Make sure not to use insect repellent on babies younger than 2 months old, or products containing oil of lemon eucalyptus or para-menthane-diol on children younger than 3 years old.
  • Wear long-sleeved shirts and long pants. There is even clothing treated with permethrin, an insecticide that repels mosquitos and other biting insects.
  • Since mosquitos are active during the day and night, you need to protect yourself whenever you are outside.
  • Use screens on windows and doors.
  • Keep mosquitos from laying eggs in or near standing water. Empty any standing water, such as dog bowls or small pools once a week.

If you are traveling

Every region of the U.S. and throughout the world has its own group of mosquito-borne diseases. If you are traveling to warm or topical areas, talk to your healthcare provider 4 to 6 weeks before your visit. You can also check the CDC website for travel alerts or the government health agency for the area you are visiting.   

For more information on mosquito-borne illnesses, you can visit these resources: