News from here and there.
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Date
2016-01
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Abstract
1 December 2015, the Pan American Health Organization
(PAHO) issued an epidemiological alert warning of a suspected
link between Zika and Guillain–Barré syndrome or microcephaly,
but with the caveat that final proof was lacking. However, the
health ministries of Brazil and Mexico, where Zika cases have
been seen, have stated that the link is Zika virus.
Zika virus disease is a mosquito-borne viral disease caused by
the Zika virus, a member of the Flavivirus genus, family
Flaviviridae. The virus is named after the Zika forest in Uganda
where it was first isolated in 1947 in rhesus monkeys in the course
of mosquito and primate surveillance. It then spread to Southeast
Asia where it caused small sporadic infections. In 2007, the first
major outbreak occurred in the Yap Islands of Micronesia. In
2013, a bigger outbreak occurred in French Polynesia, where the
estimated infection rates were 70% on some islands. There were
also reports of Guillain–Barré syndrome among adults.
The virus first appeared in the western hemisphere in February
2014, on Chile’s Easter Island. Since then, it has spread over the
length and breadth of Latin America. The first confirmed Zika
virus infection in Brazil was in March 2015. Over the past 5 years,
Brazil (population: 204 million), had 130 to 170 cases of
microcephaly each year. From January to September 2015, this
figure roughly doubled, and between October and December
2015, over 2400 new cases have been reported.
Zika virus is a 40 nanometre enveloped virus with an icosahedral
shape. It has a non-segmented single-strand, positive sense RNA
genome. The genome encodes for a polyprotein with three structural
proteins and seven non-structural proteins. The virus is primarily
transmitted to people through the bite of an infected Aedes species
mosquito (A. aegypti/A. albopictus).
The Zika virus can be transmitted from an infected pregnant
woman to her foetus during pregnancy or around the time of birth.
Currently, there are no reports of Zika virus transmission through
breastfeeding.
Sexual transmission of the virus is possible. The virus is
present longer in semen than in blood. Zika virus has been
detected in blood and other body fluids including urine, semen,
saliva, amniotic fluids as well as cerebrospinal fluid. During the
outbreak in French Polynesia, 2.8% of blood donors tested
positive for Zika virus. The virus has also been found in blood
donors in previous outbreaks. There have been multiple reports of
transmission of the virus through blood transfusion in Brazil.
Most Zika virus infections are asymptomatic. Severe infection
leading to hospitalization is uncommon and case fatality is low.
However, as mentioned above, there is a likely link between Zika
virus infection and Guillain–Barré syndrome or microcephaly.
Infection is likely to give lifelong immunity.
No specific antiviral treatment is available for Zika virus
infection. Infected people should get plenty of rest, sufficient
fluids, and analgesics and antipyretics.
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Pai Sanjay A. News from here and there. National Medical Journal of India. 2016 Jan-Feb; 29(1): 57.