Suffolk County Mosquito Control 

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West Nile Virus (WNV)

WNV can cause illness varying from a mild fever to more serious disease like encephalitis or meningitis.  WNV grows in birds and is spread from bird to bird by infected mosquitoes.  If mosquitoes infected with the virus bite horses or humans, the animal or person can become sick.  In the United States, WNV was first identified in New York during the summer of 1999.  Since then, it has spread throughout most of the continental U.S.  It's not known how WNV got to the U.S., but it has occurred naturally in Europe, Africa and Asia for many years. 

Most WNV infections do not cause any symptoms.  80% percent of people that contract WNV experience no symptoms. 20% of people experience mild symptoms. Mild WNV infections can cause fever, headache and body aches, often with a skin rash and swollen lymph glands.  In less than 1% of people infected by the virus, the disease can be serious, and at less than 0.1%, even fatal.  More severe infections can cause headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, paralysis and, sometimes at less than 0.1%, death. Persons older than 50 years of age or a compromised immune system have a higher risk of developing severe illness.

There is no specific treatment for WNV infection.  People with mild WNV infections usually recover on their own.  Doctors can provide supportive therapy for people who have more serious complications, such as encephalitis or meningitis.   

WNV usually is spread by adult mosquitoes that are infected by the virus.  Mosquitoes spread the virus by biting humans, horses, and other animals.  WNV can sometimes be spread in other ways.  For example, WNV can be spread to humans through blood transfusions and organ transplants from infected donors.  Also, it is possible the pregnant women or breastfeeding mothers who become infected with WNV may pass the virus to their baby.  Because of the unknown risk at this time and the fact that breastfeeding has well-established benefits, it is not recommended to discontinue breastfeeding.  Horses that have WNV infection cannot spread the disease directly to humans.  There is no evidence that a person can get WNV from touching live or dead infected birds.  Still, basic safety precautions should be used when handling any dead animals, including a dead bird.  If you need to move or dispose of a dead bird, use gloves or a shovel to handle it, and place it into two plastic bags (one inside the other). 

Serious illness caused by WNV is uncommon and has been identified in a small number of people in Massachusetts for the past several years.  Additionally, WNV has been found in horses, mosquitoes, and many species of birds throughout the state.  The mosquitoes that carry this virus are common throughout the state, and these mosquitoes are found in the city as well as in the woods and other less populated places. 

Massachusetts developed a Surveillance and Response Plan that serves to coordinate efforts of local officials and state agencies to reduce the risk of WNV.  The plan involves checking for the virus in mosquitoes and birds, reducing the number of mosquitoes in the environment, and educating people on ways to avoid mosquito bites.  Every year from May until the first hard frost, the Massachusetts Department of Public Health (MDPH) and local mosquito control projects collect mosquitoes from various locations around the state and send them to the State Laboratory for testing.  MDPH collects information on the number and locations of dead birds reported in the state and tests selected birds for WNV.  If WNV is identified in birds or mosquitoes, MDPH will tell local boards of health and mosquito control projects and ask them to increase their education and mosquito control activities.  MDPH provides educational materials for physicians, veterinarians, local public health officials, and the public along with updates on WNV activity in mosquitoes, horses and humans online. 

Eastern Equine Encephalitis (EEE)

EEE is a rare but serious disease caused by a virus.  The virus infects birds that live in freshwater swamps and is spread from bird to bird by infected mosquitoes.  If a mosquito infected with the virus bites a horse or human, the animal or person can become sick.  The risk of getting EEE is highest from late July through September.

The first symptoms of EEE are high fever (103° - 106°F), stiff neck, headache, and lack of energy.  These symptoms show up three to ten days after someone is bitten by an infected mosquito.  Inflammation and swelling of the brain, called encephalitis, is the most dangerous symptom.  The disease gets worse quickly and some patients may go into a coma within a week. 

There is no cure for EEE, and three of every ten people who get the disease die from it.  All doctors can do is lower the fever and ease the pressure on the brain.  Some people who survive this disease will be permanently disabled.  Few people recover completely. 

The virus that causes EEE is spread only by mosquitoes.

EEE is very rare.  Since it was first described in 1938 through 2005, 84 cases have been reported in Massachusetts.  Fifty-one of the cases occurred during outbreaks in 1938-39 and 1955-56.  Over half of the cases have been from Plymouth or Norfolk counties in southeastern Massachusetts.  Rare cases have occurred outside of eastern Massachusetts. 

Massachusetts developed a Surveillance and Response Plan the coordinates efforts of local officials and state agencies to reduce the risk of EEE.  The plan involves checking for the virus in mosquitoes, reducing the number of mosquitoes in the environment, and educating people on the ways to avoid mosquito bites.  Every year from May until the first hard frost, the Massachusetts Department of Public Health (MDPH) and local mosquito control projects collect mosquitoes from various locations around the state and send them to the State Laboratory for testing.  If the virus that causes EEE is found in mosquitoes, MDPH will tell local boards of health and mosquito control projects  and ask them to increase their education and mosquito control activities.  MDPH provides educational materials for physicians, veterinarians, local public health officials, and the public along with updates on EEE activity in mosquitoes, horses and humans online.