Zika has reached India. On Friday, the World Health Organisation announced that the first three cases of the Zika virus in the country had been detected in Ahmedabad, Gujarat. The three cases, including one of a pregnant woman, have been reported from the Bapunagar and Gopalnagar localities of the city. The organisation said the document is important as it is the first evidence about the presence of the virus in India.

A Zika virus outbreak hit South America in 2015 and 2016. Brazil, the worst-affected country, announced the end of its national Zika emergency only on May 12 this year after a sharp drop in the number of cases.

A study from the University of Oxford in April 2016 found that Asia has the most people – 1.42 billion – living in areas that are suitable for Zika virus. A large part of the susceptible population is in India with more than two million square kilometers having tropical environment suitable for the transmission of the virus.

What to watch out for

Zika is mainly transmitted by the bite of an Aedes mosquito, including Aedes aegypti that carries dengue. The virus can also be sexually transmitted.

Most people infected with Zika will show no symptoms or will have only mild symptoms of fever, rash, joint pain, conjunctivitis and, possibly, muscle pain and headaches that may last for several days to a week.

Zika infections are linked to incidences of Guillain-Barré syndrome, a nervous system disorder caused by a person’s own immune system attacking nerve cells, causing muscle weakness, and sometimes, paralysis.

The biggest danger from Zika, however, is when pregnant women get infected. The Zika virus can pass on from a woman to the foetus, which is most vulnerable to its effects. Zika can cause many developmental disorders in a foetus, the most commonly reported disorder now being microcephaly. Microcephaly, as the name suggests, is a condition of an abnormally small head caused by a much smaller number of neurons and brain material being produced during a foetus’ development.

Keep mosquitos away

The WHO recommends prevention and control measures by reducing mosquitoes populations by removing breeding sites, which are largely bodies of stagnant water, and reducing contact between mosquitoes and people. Health authorities may resort to spraying insecticides in case of outbreaks.

The WHO also recommends basic precautions to be taken by people traveling to high risk areas, especially pregnant women. These include use of repellents, wearing light colored, long sleeved shirts and pants and ensuring rooms are fitted with screens to prevent mosquitoes from entering. The WHO has not suggested any travel or trade restriction to India.

India’s response

Even though the information about these three Zika cases in India only became public on May 26, when the World Health Organisation released the news, the National Institute of Virology confirmed the first as far back as January 4 this year. According to the WHO note, the Indian government sent the information to the WHO on May 15. Until May 26, no official circular or advisory had been issued by the health department to local authorities or general public and private doctors in Ahmedabad.

The WHO note also outlines the what the government says its response has been tot he detection of Zika in the country. The government is supposed to have shared national guidelines and an action plan on Zika virus disease with the states to prevent an outbreak of Zika virus disease as well as instructions on how to contain the spread in case of any outbreak. A task force with members from the health ministry and the departments of biotechnology and health research has been set. A technical joint monitoring group is supposed to regularly review the global situation on Zika virus diseases.

Meanwhile, all international airports and ports have been asked to display on Zika information. Airport health officers along with the officials from the National Centre for Disease Control and the National Vector Borne Disease Control Programme are monitoring appropriate vector control measures at airports.

The Integrated Disease Surveillance Programme is keeping an eye out for clustered cases of acute febrile illness – fevers with uncertain causes – in communities, which are possible indications of a Zika outbreak. The Rashtriya Bal Swasthya Karyakram is monitoring microcephaly from 55 sites in the country and has reported no increase in number of cases of microcephaly as of now.

Going viral

The discovery of Zika dates back to 1947 when scientists studying yellow fever in Uganda’s Zika forest found the virus in a rhesus monkey. Human cases of Zika infection were recorded in Uganda, Tanzania and Nigeria a few years later. Between the 1960s and 1980s Zika was detected in mosquitoes and monkeys across equatorial Africa and also in Asia, including India, Indonesia, Malaysia and Pakistan.

In 2012, scientists figured out that there were two strains of the Zika virus, one of African and one of Asian lineage. The 2015-2016 Zika outbreak seems to have been caused by the Asian Zika virus that originated in south east Asia but made its way to South America having possible undergone mutations and turned virulent on the way.

The Zika scare began in March 2015 in Brazil with reports of illness characterised by skin rashes coming in from the country’s northeastern states. By July, Brazil’s health authorities reported neurological disorders in newborns associated with infection. By October, Brazil started reporting a sudden increase in microcephaly.

Zika infections were reported across central and South America – from Mexico to Paraguay and Belize to Bolivia – between November 2015 and January 2016. By this time Brazil had already announced a public health emergency. In February, the World Health Organization declared a public health emergency of international concern. Since then the Zika virus has made its way into the United States, to several Pacific Islands and now to Asia with Singapore and Malaysia reporting infections.

The Zika virus had held Brazil hostage from 2015 to 2016. The World Health Organisation lifted its international emergency over the virus on November 18 last year. Brazil lifted the national emergency on May 12 this year. The number of Zika virus cases in Brazil between January and April this year was 7,911, as opposed to 1,70,535 during the same period last year. While eight people died last year, no casualties have been reported in 2017 so far, BBC reported.