Two Powassan Encephalitis Cases Reported in Maine

In late April 2017, 2 adults in the MidCoast area in Maine were hospitalized due to infection with Powassan encephalitis.

According to the Centers for Disease Control and Prevention (CDC), patients infected with Powassan virus do not usually exhibit symptoms. However, when they do, the symptoms are usually fever, headache, vomiting, weakness, confusion, loss of coordination, difficulty speaking, and sometimes seizures. The CDC notes that infection with Powassan virus can cause meningitis as well as encephalitis (inflammation of the brain). Encephalitis resulting from a Powassan virus infection is fatal in about 10% of cases.

In November 2016, an infant in Connecticut was the first human in the state to be diagnosed with Powassan virus. The patient developed severe complications, including seizures “that included rightward eye deviation and right arm stiffening,” for which he was hospitalized. According to the infant's physicians, MRIs showed signs consistent with encephalitis. After the infant was treated for the seizures, he was released from the hospital, only to develop other complications 1 month later. Researchers reporting on this case strongly recommended that, in areas endemic for ticks, patients presenting with encephalitis be tested for Powassan virus.

The 2 most recent cases were reported to the Maine Centers for Disease Control and Prevention in late May 2017, one month after patients were hospitalized. The patients were diagnosed based on testing conduced at the CDC in Fort Collins, Colorado; they have since been release from the hospital and are now recovering. There have only been 7 cases of Powassan virus reported in Maine since 2000 (not including these 2 most-recent cases).

Powassan virus is transmitted by infected Ixodes scapularis ticks, as well as several other Ixodes ticks that are not known to bite humans. Maine State Epidemiologist, Siiri Bennett, MD, said in a press release, “Powassan, although rare, can be serious, so it is important to be aware of your surroundings and take steps to avoid being bitten by ticks. Ticks are found in wooded and bushy areas, so use caution if you go into these areas.” She then went on to note that using the “No Ticks 4 Me approach,” can lower the risk of tick exposure as well as the risk for tick-borne diseases.

The No Ticks 4 Me approach includes wearing light-colored clothing that leaves ticks visible if they are on clothes, and wearing long-sleeve shirts and long pants so as to reduce the amount of exposed skin. The approach also includes using United States Environmental Protection Agency (EPA)-registered tick-repellent or Permethrin-treated clothing. Ticks can also hide on pets. Although Permethrin-based products are safe to use in dogs, it is recommended to avoid their use in cats, as it can be poisonous to them.

As part of the approach, individuals are also urged to avoid “wooded and bushy areas with high grass.” It is recommended that those who do go into nature “stay in the middle of trails whenever possible,” and check their bodies for attached ticks, daily, especially once out of tick-endemic areas. In addition, showering immediately after returning from such areas is also highly recommended so as to remove ticks from the body, and protect from disease.