After dengue and chikungunya, the Aedesaegypti mosquito delivers a new shock, Zika fever
DOWN TO EARTH
The world is in the throes of yet another infectious disease outbreak. A report released by the World Health Organization ( who) on February 5 says that the Zika virus has spread to 33 countries. Brazil, the worst affected , has between 0.5 million to 1.5 million suspected cases.
Zika was first isolated from the rhesus monkey in Uganda’s Zika forest in 1947 and in humans in 1952. But in the next five decades only 15 cases were reported from Africa and Southeast Asia. In 2007, there was a massive spread of this zoonotic disease (infections that emerge in animals and jump to humans) in Yap, an island group in the Western Pacific, and things have been getting worse since then. The virus went to other Pacific Islands before reaching Brazil, from where it spread rapidly to other parts of South America, Central America, Mexico, and the Caribbean. Things came to a head on February 1 when the huge number of cases forced who to declare it a Public Health Emergency of International Concern. This is only the fourth time who has declared a state of emergency.
The Zika virus, spread by Aedes aegypti and Aedes albopictus mosquitoes, usually causes mild fever, aches, rashes and conjunctivitis. But this time, the incidence of microcephaly (a condition of underdeveloped heads and brain defects) in children born to women who suffered from the infection during pregnancy is much higher. Till January 22, the virus had caused 3,893 suspected cases of microcephaly only in Brazil. This is over 30 times the number of suspected cases reported by the country in any given year since 2010. Seven of the 33 Zika-affected countries have reported a rise in cases of microcephaly. The virus also seems to have a link with Guillain-Barré Syndrome, a progressive neurological disease that causes paralysis.
The possible links have turned the Zika virus from a mild threat to an alarming one. In the Americas, the virus has spread rapidly mainly because the population has never been exposed to this pathogen and has, therefore, not developed immunity. Only two countries in the Americas—Canada and Chile—are completely free of the virus.
A baby is diagnosed with microcephaly in Recife, Brazil. The neurological disorder is associated with Zika