State health officials raise risk level for West Nile virus

State public health officials are urging residents to take precautions against mosquito bites following the discovery of several West Nile virus-positive mosquito samples — including one in Canton — and a rash of WNV human infections found within the past week.

The Massachusetts Department of Public Health (DPH), citing an overall increase in infected mosquitoes identified throughout the state this year, announced on August 21 that it was raising the risk level for West Nile virus from “low” to “moderate” in every Massachusetts city and town — marking only the second time since WNV was first detected in the commonwealth in 2000 that the department has raised the risk level statewide.

West Nile virus risk map (Source: Mass. Department of Public Health). Click to enlarge

Just days later, DPH officials announced the first three human cases of WNV in Massachusetts in 2018, along with a single case of an infected horse that became severely ill and had to be euthanized. On Monday the state announced a fourth human case and subsequently raised the threat level for 11 greater Boston communities from “moderate” to “high.”

The city of Boston, which directly borders Canton on the southern edge of Hyde Park (near the Fowl Meadow wetland area), is among the municipalities with a “high” risk level.

“Several individuals from the same area have developed West Nile virus,” said Public Health Commissioner Monica Bharel, MD, MPH. “That means that there is an increased risk in this specific area and that additional people could become infected. We are particularly concerned about people over 50 and those who are immunocompromised as they are the ones most likely to develop WNV disease.”

All four of the confirmed human cases seen to date have involved a female patient over age 50, including two in Middlesex County, one in Worcester County, and one in Suffolk County. Two of the patients had to be hospitalized for their illness.

Additionally, the DPH has reported 323 WNV-positive mosquito samples throughout the commonwealth this year, with the highest concentrations occurring in Middlesex and Worcester counties. Norfolk County has seen 22 positive samples to date, including one in Canton that was collected on August 8 and another in Stoughton collected on August 15.

West Nile Virus is usually transmitted to humans through the bite of an infected mosquito. Most people infected will have no symptoms; however, when present, symptoms tend to include fever and flu-like illness. In rare cases, more severe illness can occur.

The DPH also tests mosquito samples for eastern equine encephalitis (EEE), a rare but serious arbovirus with more severe symptoms than those for WNV. To date, there have been no EEE-positive mosquito samples or human cases reported in Massachusetts this year. Outbreaks usually occur every 10-20 years with the most recent outbreak lasting from 2010 to 2013, during which time there were over 400 positive mosquito samples and 11 human cases, including two fatalities.

State health officials are encouraging those at high risk for WNV (people over 50) to consider avoiding outdoor activity at dusk and dawn. Further, they advise local boards of health to work directly with their mosquito control district to determine appropriate control measures …

See this week’s Canton Citizen for more information, including tips for preventing infection. Click here to order your subscription today (also available in digital form).

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Posted by Jay Turner on Sep 1 2018. Filed under News. Both comments and pings are currently closed.