Modified from Massachusetts Department of Public Health Web site

One in a Five year old child an another in an 83 year old man

Eastern Equine Encephalitis (EEE) characteristically affects either the youngest or oldest members of the population. This may be because most young children will not have had subclinical cases of the disease and therefore developed immunity. It is also possible that the virus may pass across the blood-brain barrier more readily in the young. In the old, susceptibility to EEE probably results from a compromised immune system.

In Massachussetts, a 5-year-old girl from Halifax and an 83-year-old man from Kingston died after being diagnosed with EEE.

The young girl became ill August 26, 2005 and died September 4. Testing at the Massachusetts State Laboratory Institute revealed  EEE infection. The elderly man became ill on August 21 and died on August 26. Confirmation of EEE in his case was made a week after his death and was dependent on a blood specimen drawn before his death and testing of tissue samples that were provided after his death.

Also a case in a 63-year-old woman from Duxbury was reported. Although she was the first case diagnosed and reported, her onset was on August 26 after the man from Kingston had already developed symptoms.

“It’s critical that residents protect themselves from mosquito bites,” said Dr. Al DeMaria, DPH Director of Communicable Disease Control. “Mosquitoes will be biting until the first frost.”

The Massachusetts Department of Public Health (DPH) has also confirmed reports of EEE in two horses: one in Haverhill and one in Wrentham. In the 2005 season both EEE virus and West Nile virus (WNV) were detected in mosquitoes and birds in a number of communities across the Commonwealth. Thus, on the basis of testing of mosquitoes, birds and horses, large parts of the state are at risk for EEE and WNV infection. Many mosquito pools from the Kingston, Duxbury and Halifax area of Plymouth County have been positive for EEE virus, with the first evidence of EEE virus in the state in mosquitoes from that area collected in late July. New Hampshire reported EEE in four people, 5 horses and in numerous birds.

In 2004, four human cases of EEE, resulting in two fatalities were confirmed in Massachusetts residents from Brockton, Foxboro, Holbrook and Middleboro. Among 222 specimens submitted to the State Laboratory in 2005, a human case of disease with West Nile virus (WNV) was not identified. There were no confirmed cases of WNV infection in people in 2004 in Massachusetts.

The Plymouth County Mosquito Control Program has been applying intensified control measures in the Kingston, Duxbury and Halifax area for over a month, with interventions against both mosquito larvae in standing water and adult mosquitoes. Enhanced mosquito surveillance has also been in place. DPH is also contacting hospitals in Bristol, Norfolk and Plymouth counties to review reporting and sample submission protocols for suspect cases of encephalitis.

Mosquitoes are still actively biting and will be biting until the first frost. Although their numbers may be down somewhat, they may be more likely to be infected since the amount of virus increases over the warm season. DPH advises the public to take special efforts in protective measures to avoid mosquitoes and mosquito bites into September, one of the highest risk months in Massachusetts for human infections from EEE virus and WNV. There is special concern about exposure to mosquitoes during outdoor recreational activities, related and unrelated to school opening. An advisory will be going out to boards of health, health departments, schools, libraries and other places about the threat from mosquitoes and infections spread by them.

EEE virus infection, though rare, causes severe illness in nearly every case and mortality of 30-50 percent in clinical cases. WNV causes severe illness in less than 1 percent of those persons who are infected and mortality is 20 percent among persons with severe disease. The risk of severe illness from West Nile virus infection increases with age.

 

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