After dengue and chikungunya, the Aedes mosquito is delivering a new emergency— Zika. Down To Earth looks into the reasons behind the spread and the threat the virus holds
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. Governments of Brazil, Colombia, Jamaica, El Salvador and Venezuela have advised women not to plan pregnancies till the virus is controlled. The US Centers for Disease Control and Prevention too has advised pregnant women not to travel to Brazil and other countries with Zika virus outbreaks. Expert say that in order to understand the full impact of the virus, pregnant women and babies will have to be monitored for a long period.
In light of the correlation of the virus with microcephaly and Guillain-Barré Syndrome, WHO got experts together to study the link. The first meeting of the Emergency Committee was convened on February 1 and though no direct link between the Zika virus and microcephaly was established, the observed correlation was strong enough for the committee to call the outbreak a Public Health Emergency of International Concern. David Heymann, chair of the emergency meeting, explained that while the Zika virus per se was not the health emergency, its suspected link to microcephaly and neurological disorders makes it one.
“A coordinated international response is needed to improve surveillance, the detection of infections, congenital malformations and neurological complications, to intensify the control of mosquito populations, and to expedite the development of diagnostic tests and vaccines to protect people at risk, especially during pregnancy,” said WHO Director General Margaret Chan in the meeting. But despite this, the committee did not see the need to recommend restrictions on travel or trade to prevent the spread of Zika, probably because of the financial implications.
And the financial impact is estimated to be huge.
Geraint Johnes, professor of economics, Lancaster University, in his article in The Conversation, an independent news and commentary website, says that with Brazil’s annual carnival and the Rio Summer Olympics (beginning August 5), Brazil is likely to suffer huge losses in tourism. During these events, the earnings in the tourism sector are as big as 10 per cent of the country’s gross domestic product. Using data collected during the 2003 SARS outbreak in Malaysia, Singapore, Hong Kong and China, where losses in tourism sector were as much as 20 per cent, he said Brazil could lose US $47 billion in the year.
Apart from the financial loss, the virus has engendered a debate that has religious undertones. Most of the affected countries are Roman Catholic where contraception and abortions are looked down upon. Though governments of affected countries, such as Brazil, are mulling proposals to allow abortions, the choices women are faced with are tough.
How ready is India?
The declaration of the emergency by WHO has made India take notice of the threat. On February 2, the Union Ministry of Health and Family Welfare issued guidelines on managing the Zika virus and appointed the National Centre for Disease Control in Delhi as the nodal agency for investigating outbreaks in the country.
The ministry has also issued travel advisories and suggested that people avoid non-essential travel to affected countries. According to the guidelines, pregnant women or women who are planning pregnancy should defer travelling to the affected areas. It suggests that travellers diagnosed with fever within two weeks of return from an affected country should report to the nearest health facility.
The guidelines also call for pregnant women who have travelled to Zika-affected areas to mention their travel during antenatal visits in order to be assessed and monitored appropriately. For enhancing surveillance, the ministry has said that the Integrated Disease Surveillance Programme (IDSP), through its community and hospital-based data gathering mechanism, would keep track of areas where a large number of cases of acute fever are reported. IDSP would also advise its state- and district-level units to look for clustering of cases of microcephaly among newborns and reporting of Guillain-Barré Syndrome. The Maternal and Child Health Division (under National Health Mission) would also advise its field units to look for clustering of cases of microcephaly among newborns.
Though, no case of Zika has been reported in India so far, the virus has a history in the country. In reply to Down To Earth, D T Mourya, director of National Institute of Virology (NIV), Pune, said that prevalence studies on the Zika virus had been carried out as early as in 1952-53 by the institute and showed presence of antibodies in humans in several parts of central and western India. He also claimed that India is prepared to deal with any challenge and NIV has the basic diagnostic tools to detect the virus.
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