Dr KK Aggarwal
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.
Dr KK Aggarwal
Padma Shri Awardee
President Elect Confederation of
Medical Associations in Asia and Oceania
(CMAAO)
Group Editor-in-Chief IJCP Publications
President Heart Care Foundation of
India
Past National President
IMA
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