Pune has local transmission of Zika virus, say experts

Even though Pune has reported Zika cases from select parts of the city, the virus may have spread to most areas and it’s possible that more people may have contracted it, said experts from ICMR-National Institute of Epidemiology (ICMR-NIE), adding fewer test not showing the actual number of cases.

According to experts, the cases have been reported in patients with no travel history to Zika-affected areas or cohabitation and there is local transmission of Zika virus in Pune.

Till Sunday, the city has reported 11 cases, mostly from Mundhwa, Erandwane, Kothrud, and Ambedgaon areas.

Dr Manoj Murhekar, director and scientist, ICMR-NIE, said, “The Zika infection cases in Pune are sporadic in different parts of the city, so we can say there are mosquitoes in several locations which are infected.”

“It means people have acquired the infection locally. Evidence of infection in mosquitoes is important to be found. In Zika virus the control measures remain the same in every vector-borne disease. Mosquito measures are difficult without the people’s participation,” he said.

As per the experts, although the percentage of virus-infected mosquitoes is less, there is a need to strengthen entomological surveys and test a large number of mosquitoes regularly.

India reported the first Zika case from Gujarat in 2016. Since then, many other states namely Tamil Nadu, Madhya Pradesh, Rajasthan, Kerala, Maharashtra, Uttar Pradesh, Delhi, and Karnataka have reported cases subsequently.

Another expert from ICMR-NIE, said, that in Kerala, there was a Zika virus outbreak in one locality and the focus was only on one area and the virus transmission was not spread across and similar was the case in Jaipur.

“The majority of the Zika virus infection cases are subclinical and asymptomatic and only symptomatic people are tested. The cases reported in Pune city could be just the tip of the iceberg and there is a possibility the virus transmission is everywhere,” said the official.

Dr Murhekar, said, that in India fortunately no adverse effects like microcephaly were detected in the Zika outbreak in Rajasthan amongst pregnant women.

“The ongoing monsoon season and controlling mosquito breeding of the vector will be a challenging task for health officials. People should also ensure to take precautions as Zika cases have been reported,” he said.

Mosquito surveillance is important to find out how many mosquitoes are infected, said Dr Murhekar.

“If it is a low-level infection in the vector, you need to sample a lot. When the infection in the mosquitoes is common you can detect it early. But when a smaller percentage of mosquitoes are infected, you need to sample a lot. After continuous efforts, the infection might be found in some of the mosquitoes. However, if the mosquitoes test negative it doesn’t mean there is no Zika virus, as already the infection is reported in humans,” said Dr Murhekar.

The ICMR-NIE, experts explained in case the virus positivity is around one per cent in the mosquitoes, it can be detected in one mosquito if 100 mosquitoes are tested. If the positivity is 0.1 percent over 1000 mosquitoes should be caught and tested. Similarly, if the positivity is 0.01 large mosquitoes need to be tested from the Zika-affected area. This mosquito surveillance should be continuous and done periodically.

Dr Murhekar said the public health department has started systematic surveillance in Pune city and it needs to be strengthened to find out the virus transmission in which areas.

“Strengthening surveillance for Zika, mosquito control measures for adult mosquitoes and larvae. Monitoring pregnant women who tested positive for the virus infection should be done. People should not panic even if they get infected with the virus infection,” he said.