Powassan virus disease: An emerging tick-borne illness

Cases of a tick-borne disease “Powassan virus disease” are being reported from the United States. Two cases were reported in New Jersey in June and now another case has been reported this month in Maine, following which the Maine Center for Disease Control and Prevention (CDC) issued an advisory to physicians that more cases could be possible and suggested that doctors consider testing for the disease in patients with unexplained encephalitis, meningitis or high fever during the summer and early fall, as reported by CNN. Powassan virus disease is a notifiable disease in the US.

The Powassan virus is named after the town of Powassan, Ontario, where it was identified in 1958 in a young boy who eventually died from the illness.

About Powassan virus disease

  • Powassan virus disease is a rare tick borne disease. Although still rare, the number of reported cases of people sick from Powassan virus has increased in recent years.
  • Human Powassan virus infection is endemic in the US, Canada and Russia.
  • Etiology:Powassan virus disease is caused by the Powassan virus, a flavivirus.
  • Transmission:Powassan virus is spread to people by the bite of an infected tick. Three types of ticks transmit the virus: Ixodes cookei (groundhog tick), Ixodes marxi (squirrel tick) and Ixodes scapularis (blacklegged or deer tick). Of the three, the deer tick is more likely to bite humans; it also transmits Lyme disease. Powassan virus cannot spread from person to person.
  • Incubation period:1-4 weeks
  • Symptoms:Initial symptoms are non-specific and include fever, headache, vomiting and generalized weakness. In severe disease, encephalitis, meningoencephalitis, or aseptic meningitis may occur, presenting as confusion, loss of coordination, seizures, speech problems (aphasia, dysarthria), paresis or paralysis.
  • Differential etiology:Herpes simplex virus, enteroviruses, West Nile, St. Louis encephalitis, La Crosse, Jamestown Canyon, eastern equine encephalitis viruses
  • Clinical diagnosis:Suspect Powassan virus disease in any person with a febrile or acute neurologic illness who has had recent likely exposure to Ixodes species ticks in Powassan virus endemic areas mainly in the late spring, early summer and mid-fall when ticks are most active.
  • Laboratory diagnosis:Powassan virus-specific IgM and neutralizing antibodies in serum and CSF (ELISA); confirmatory test by neutralizing antibody testing (plaque-reduction neutralization test [PRNT]) of serum specimens.
  • Treatment:There is no specific treatment; clinical management is supportive.
  • Prevention:There is no vaccine available; infection is prevented by preventing tick bites by avoiding wooded and bushy areas with high grass in endemic areas, wearing long sleeves and pants, using insect repellents (DEET, picaridin or IR3535) to discourage tick attachment and check for ticks and remove them before they attach to the skin (often found in the groin, axilla and scalp).
  • Prognosis:Approximately 10% of Powassan virus neuroinvasive disease cases are fatal; about 50% of survivors have long-lasting neurologic deficits, such as headaches, muscle weakness, focal paralysis, or cognitive difficulties.

Earlier this week, the Indian Council of Medical Research (ICMR) and the National Centre for Disease Control (NCDC) identified 10 emerging viral infections that could pose a threat to public health in India.

  1. Middle East Respiratory Syndrome coronaviruses (MERS-CoV)
  2. Ebola virus
  3. Avian influenza (H7N9)
  4. Avian influenza (H9N2)
  5. Yellow fever virus
  6. Usutu virus
  7. Tilapia novel orthomyxo-like virus
  8. Cyclovirus
  9. Banna reo Virus encephalitis (China) like JE
  10. Canine parvovirus (causes dog gastroenteritis)

Although cases of Powassan virus disease have not been reported in India, with the blurring of international boundaries and increasing international travel, there is now a threat of global spread of any infectious disease in any part of the world where it was not earlier known.

Prevention and control of epidemics requires commitment on the part of policy makers, administrators and all stakeholders towards public health. It is equally important to educate the general public so that they can take timely precautions.

Will we be ready to tackle future epidemics? The answer lies in anticipation and preparedness.

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