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The Maine Centers for Disease Control has announced the death of an unnamed person from Powassan disease, caused by a virus spread by ticks.
Powassan virus is a flavivirus, part of the same family as dengue and yellow fever. It causes encephalitis (inflammation of the brain) as well as a variety of less serious symptoms. Most cases come from the places where the carrier ticks are common – wooded areas around the Great Lakes region of North America and the US North East.
Powassan disease was first reported in Canada 1958 in the town of the same name, and remained very rare for decades thereafter, although those cases that have been reported have spanned much of the northern hemisphere. The US now suffers 25 cases a year, the Maine Department of Health and Human Services (DHHS) notes in an announcement reporting the unnamed man's death. However, this is up from around 10 pre-2015, and there are signs the rise may be accelerating.
With six tick species, mostly members of the Ixodes genus, able to spread the disease the potential for rapid growth is there. Fortunately, some of these seldom bite humans, preferring groundhogs and squirrels, so most cases of Powassan are from I. scapularis, also known as the blacklegged or deer tick.
“Ticks are active and looking for a host to bite right now,” said Nirav D. Shah of the Maine CDC. “I urge Maine people and visitors to take steps that prevent tick bites.”
As with other tickborne diseases, people may not even notice they have been bitten at the time, and symptoms take time to appear, in Powassan's case usually between a week and month later. Not everyone infected gets sick, and as we know from other viruses, the numbers of asymptomatic infections are probably dramatically undercounted.
The Maine DHHS lists symptoms as: “Fever, headache, vomiting, weakness, confusion, seizures, or memory loss.” More rarely, but more seriously, there are cases of brain or spinal cord inflammation, which can lead to death such as in this case.
In this case no details have been released other than that the victim lived in Waldo County, and the CDC believes infection probably occurred within state.
Most tick-borne diseases, including Lyme disease, are bacterial, and can be treated with antibiotics if diagnosed early enough. Being a virus, Powassan is far less susceptible to treatment once bitten so health authorities recommend avoiding tall grass where ticks are common, wearing approved repellants on the skin and Permethrin on clothing and checking for ticks daily, particularly after leaving tick habitat.
Among the earlier victims of Powassan was former US Senator Kay Hagan, who became sick with the disease after a tickbite in 2016. She never really recovered and died three years later.
It's uncertain why numbers are rising, although climate change is always a possibility.
In the face of disturbing evidence of the collapse of global insect populations it's the invertebrates we don't want that seem to be among the rare exceptions.
