(NBC)- Parts of Massachusetts are at “critical risk” for a rare but potentially deadly mosquito-borne disease after lab tests confirmed the first human case of Eastern equine encephalitis in the state since 2013.
The male patient is over 60 and lives in Plymouth County, the Massachusetts Department of Public Health announced Saturday.
The virus — which is more virulent than West Nile — can cause inflammation of the brain that leads to death in about one-third of cases. People who do survive are often left with brain damage.
“We are asking residents to take this risk very seriously,” said Dr. Monica Bharel, the state’s public health commissioner, in a statement. The virus has been found in 227 mosquito samples this year, the Massachusetts Department of Public Health noted.
The highest chance of infection in humans is typically August, officials said. Aerial sprays have been targeting Bristol and Plymouth counties in Massachusetts to reduce the mosquito population. Nine communities in the region are now at critical risk for the EEE virus, with an additional 15 communities in southeastern Massachusetts deemed to be at high risk and 18 at moderate risk.
“It’s concerning from a public health point of view, no question about it,” Joe Conlon, a retired U.S. Navy entomologist and spokesman for the American Mosquito Control Association, told TODAY.
“(But) it’s not a very wide-spread disease, thank goodness… it’s not common like West Nile virus.”
Only a few cases of EEE are reported in the U.S. each year, with most infections happening in the Atlantic and Gulf Coast states, and some in the Great Lakes region, according to the Centers for Disease Control and Prevention. Just six cases were reported in all of 2018.
The virus grows in birds that live in swamps. When a mosquito that feeds on both birds and mammals bites an infected bird, it can then transmit the virus to horses and other animals and, in rare cases, people.
Symptoms start four to 10 days after a person is bitten and include headache, high fever, chills and vomiting. As the disease progresses, the patient can suffer from disorientation, seizures and coma. There is no specific treatment.
“They give you palliative care and you either get better or you die,” Conlon said.
As humans move closer to and deeper into hardwood forests, they’re increasing their risk, he noted. Climate change plus human travel and migration may also play a role in mosquito-borne diseases, potentially exposing half of world’s population to disease-spreading mosquitoes by 2050, an analysis published in Nature Microbiology in March found.
But other studies have found the ban on the insecticide DDT, rather than a warming climate, may be responsible for mosquitoes thriving in the U.S. It appears many factors are at play.
“If the climate change that’s occurring is producing higher temperatures and more rainfall, that’s going to abet this type of disease transmission,” Conlon noted.
“In addition, the world is getting smaller. Tourism and travel is getting a lot cheaper, a lot more widespread. We’re putting travelers in contact with these exotic diseases that are a seven-hour plane flight away. They’re bringing these diseases in some cases back to the U.S.”
His main concern now is keeping mosquito-borne disease like Rift Valley fever, found in Africa, and yellow fever, found in South America and Africa, out of the U.S.