Since Zika has been detected in parts of Asia and Africa for decades, scientists have been flummoxed as to why the virus has not yet affected Africa or India
New Delhi: A year ago, Zika fever was unheard of. The few who knew about the disease saw it as an innocuous one associated with mild fever and rashes. However, in the last one year, it has proved fatal with newborns suffering from neurological disorders and the disease spreading to more than 40 countries.
Between 2007 and 2014, only 13 nations reported evidence of Zika virus transmission. But since 2015, 44 countries have reported Zika virus outbreak with the latest being Peru and Saint Barthélemy.
In February, the World Health Organization (WHO) declared that the recent association of Zika infection with clusters of microcephaly and other neurological disorders constitutes a Public Health Emergency of International Concern.
It all started in early February 2015 when doctors in northeastern part of Brazil observed a sudden rise in the number of people complaining about mild illness, with or without fever, characterised by rash, fatigue, joint pains, and red eyes; results for dengue and chikungunya tests came negative.
By March end, Brazil informed the WHO that nearly 7,000 cases of an illness characterized by skin rash had been reported in six northeastern states, but no one knew the cause.
On 7 May last year, tests conducted at Brazil’s national reference laboratory conclusively identified Zika in several samples. But the threat of the disease fully emerged in mid-July 2015 when Brazil informed WHO of a surge in the detection of neurological disorders, including Guillain-Barré syndrome. This was also observed later in other countries with large outbreaks, including Colombia, Dominican Republic, El Salvador, Honduras, Suriname, and Venezuela.
In most of these countries, the symptoms was detected about three months after virus circulation was confirmed, raising suspicions that Zika was the cause. In October 2015, Brazil informed the WHO about 54 cases of microcephaly or abnormally small brains among newborns were detected since August.
The suspicions were proven correct after evidence to establish causation emerged in March this year when the WHO concluded that there is scientific consensus that Zika virus is a cause of microcephaly and Guillain-Barré syndrome.
In April, a paper by scientists from the US Centers for Disease Control and Prevention, published in the New England Journal of Medicine, established the causal relationship between Zika infection during pregnancy and microcephaly in newborns. At that time, cases of microcephaly had been reported in Brazil, Cabo Verde, Colombia, Martinique, and Panama as well as French Polynesia.
Zika and India
A study led by University of Oxford last month said that global tropical and subtropical regions inhabited by over 2.7 billion people—including 2 million sq. km in India—are at high risk of Zika.
But no Zika cases have been detected in India till now. Union health ministry’s Indian Council of Medical Research (ICMR) is monitoring Zika virus in India. Its institute National Institute of Virology (NIV), Pune is the nodal agency for the same.
India has 10 NIV-monitored National Virology laboratories which are responsible for testing viral infections like dengue. “Cases which are found negative for dengue and chikungunya are being tested for Zika. NIV has Zika testing kits," said ICMR director general Soumya Swaminathan. She said so far no case has tested positive for Zika in India.
The authors of the Oxford study found it surprising that no large outbreaks have been reported in Asia and Africa despite many of these areas being highly suitable for transmission.
“This could be due to under-reporting, misdiagnosis, or a high level of immunity in the human population, where the virus has been present for a long time. It was first discovered in Uganda in 1947," noted the authors.
Since the virus has been detected in parts of Asia and Africa for several decades, scientists have been flummoxed as to why the virus has not yet affected Africa or India.
“Endemicity is assumed, though no one knows whether presence of the virus over time has resulted in widespread or low-level immune protection or possibly no protection at all," said the WHO report.
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