More deadly mosquito trouble may be ahead, federal officials warn

A mosquito being examined by a biologist. Rick Bowmer/File/Associated Press

Federal public health officials are sounding the alarm about Eastern equine encephalitis, saying this year’s outbreaks in multiple states, including one that killed three people in Massachusetts, may be a warning sign of future trouble from the deadly disease and other insect-borne viruses.

“This year’s EEE outbreaks may ... be a harbinger of a new era of arboviral emergencies,” officials from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, said in a commentary last week in The New England Journal of Medicine.

“Given the near certainty of future emergences, arboviruses constitute a real and present danger,” the officials said.

The officials, who included NIAID director Anthony S. Fauci, said that in the summer and fall of this year, nine US states had reported 36 human cases of EEE, 14 of which were fatal.

The officials also noted that in recent years, the Americas have witnessed a “steady stream” of other arboviruses (arthropod-borne viruses), such as dengue, West Nile, chikungunya, Zika, and Powassan, as well as increasing numbers of travel-related cases of other arbovirus infections.

A colorized electron microscope image of mosquito salivary gland tissue. EEE virus particles are in red.CDC/Fred Murphy/Sylvia Whitfield

Ninety-six percent of people infected with EEE don’t get symptoms. But one in three people who come down with symptoms die. Most of the remainder suffer permanent, often severe, brain damage. No antiviral drug has been demonstrated to be effective against EEE. The mainstay of the treatment is supportive care, often including admission to an ICU and being placed on a ventilator, officials said.

Several vaccines are in development, the officials said. However, they warned, “there may not be strong incentives to proceed to advanced development and licensure because of the nature of the disease: outbreaks are rare, brief, and focal, and they occur sporadically in unpredictable locations, making it difficult to identify an appropriate target population for vaccination.”

The officials said state and local health departments can provide early warning of EEE by surveilling horses, birds, and mosquitoes, but “even these blunt prevention tools are continuously threatened by underfunding of public health efforts.”

In a February article in The American Journal of Tropical Medicine and Hygiene, a different group of federal researchers said reports of mosquito- and tick-borne illlnesses had more than tripled from 27,388 in 2004 to 96,075 in 2016, with tick-borne diseases increasing steadily and “interspersed, sporadic outbreaks” of mosquito-borne illnesses. The article called for a “national strategy” to defend against the diseases.

The officials said in the New England Journal of Medicine commentary that they agreed with the calls for such a strategy. “Arbovirus threats are not easily thwarted by piecemeal efforts,” they said.

They also noted that changes in climate and weather were “cause for additional concern, since they may affect the life cycles and geographic distribution of arthropod vectors and viral transmission patterns.”

“Although EEE is not yet a disease of major national importance, this year’s spike in cases exposed our inadequate preparation for emergent disease threats. Though the best way to respond to these threats is not entirely clear, to ignore them completely and do nothing would be irresponsible,” the officials said.