The Indian Council of Medical Research told the Ministry of Health and Family Welfare and the Gujarat government about the three cases of Zika virus infections in Ahmedabad as soon as they were confirmed positive, said Dr Soumya Swaminathan, director-general of the apex body for medical research in the country. The first case was confirmed on January 4.

However, the government appears not to have passed this information to the local authorities in charge of disease prevention and control measures. Said Dr Vijay Kohli, entomologist, Ahmedabad Municipal Corporation: “We got to know about Zika cases in Ahmedabad after reading about it on the WHO website.”

Local health authorities under city corporations conduct disease control activities such as controlling the spread of the mosquitoes, informing the public and treating the infected people.

Within the Indian Council of Medical Research, the information remained within a “core group” that deals with virology, said Swaminathan. More than 50 laboratories have been trained to test for the Zika virus in India. Asked whether they were alerted that the disease had entered India, Swaminathan said they were not.

A new disease enters India

In March 2015, Brazil began to report a spurt in cases of microcephaly, where babies are born with abnormally small heads. The scientific consensus is that the microcephaly cases were caused by the Zika virus. The virus is mainly transmitted by the bite of the Aedes aegypti mosquito. People with the disease can have symptoms including mild fever, skin rash, conjunctivitis, muscle and joint pain, malaise or headache.

India began surveillance for the Zika virus in July 2016. So far, 34,233 human samples and 12,647 mosquito samples have been tested for the presence of Zika virus. No mosquito samples tested so far have shown the presence of the virus.

In March 2017, the Minister of State for Health and Family Welfare Anupriya Patel, in answer to a question in the Lok Sabha, said: “So far only one case of laboratory positive zika virus disease has been detected in Ahmedabad, India as part of routine laboratory surveillance in January, 2017.”

But the information did not become widely known until the World Health Organisation published an update on May 26, saying it had received information from India about three cases of Zika infections.

All three cases – a 64-year-old man, a 34-year-old new mother and a 22-year-old pregnant woman – have been reported from the Bapunagar locality of Ahmedabad. The cases were first detected in BJ Medical College in Ahmedabad. The three cases were re-confirmed as positive by National Institute of Virology.

The 34-year old woman was detected with Zika in January, when she was still pregnant. The other two cases were confirmed by end of March, said Swaminathan. However, Indian government sent the information to the WHO only on May 15.

Union health ministry officials have been unavailable for comment and have not issued an official statement at the time that this story was published.

Timeline of Zika in India: What we know so far