After flood, Gujarat prepares for bigger peak of vector, water-borne diseases

Heavy and incessant rainfall, especially in central Gujarat districts of Vadodara, Anand and Kheda, as well as Dwarka, Jamnagar, Morbi and Porbandar in Saurashtra, have led to severe flooding this week. While flooding itself has taken a toll – both in terms of lives, livelihoods and homes – its aftermath, the stagnation of water, is expected to cause a surge in vector-borne diseases.

While rainfall has now slowed down to a trickle, the mayhem caused this week has left districts with stagnant pools of water, which are set to become breeding sites for Aedes Aegypti mosquitoes that are carriers of dengue, chikungunya and zika viruses.

A health department official said, “The rain washed out all mosquito breeding sites. So, the peak in terms of vector disease cases that was to come by the end of August, will not come. However, there is bad news. Due to incessant rainfall and flooding, waterlogging is rampant.”

“The stagnant water needs to be cleared otherwise, mosquitoes that will likely develop in such new breeding sites, will mature in 8 to 10 days, get infected and spread the infection to humans… We will start getting cases by the end of two weeks. This peak will be much worse,” the official added.

“This is an unexpected situation and vector breeding will take place at areas where it had not happened before,” said Dr Rajendra Kumar Baharia, Scientist B and officer in charge of Gujarat unit of National Institute of Malaria Research.

He added, “By mid-September, we should see another rise in vector-borne diseases. Hospitals need to be ready for this. Meanwhile, waterlogging needs to be cleared immediately. All potential breeding sites need to be destroyed…”

Experts warned of a situation similar to the one witnessed in the aftermath of the 2006 flood. Dr Bhavesh Modi, Professor of Community Medicine at AIIMS Rajkot, said, “After heavy rainfall in 2006, several districts in Gujarat, including Surat, were flooded. This led to a major outbreak of chikungunya cases across the area, which also reached Ahmedabad.”

According to a report from World Health Organization (WHO), from February 2006 to October 10, 2006, WHO SEARO (Regional Office for South-East Asia) had reported that 151 districts in eight states or provinces of India were affected by chikungunya. These were Andhra Pradesh, Andaman & Nicobar Islands, Tamil Nadu, Karnataka, Maharashtra, Gujarat, Madhya Pradesh, Kerala and Delhi. More than 1.25 million suspected cases were reported across the country during this period, with some areas reporting “attack rates” of 45 per cent, the report had said.

As per a 2008 study conducted by Dr Dileep Mavalankar – former director of Indian Institute of Public Health – and published in the Journal of Emerging Infectious Diseases, “India reported 1.39 million cases of chikungunya in 2006 with no attributable deaths… Ahmedabad reported 60,777 suspected cases…”

“A total of 2,944 excess deaths occurred during the chikungunya epidemic (Aug-Nov 2006) when compared with the average number of deaths in the same months in the previous four years. These excess deaths may be attributable to this epidemic. However, a hidden or unexplained cause of death is also possible. Public health authorities should thoroughly investigate this increase in deaths…,” it had said.

The Gujarat government, hoping to avoid a disaster in terms of high caseload in the aftermath of the recent flood, has deployed 40,000 personnel to check for stagnant water sites. Hospitals have also been asked to be prepared to accommodate an increase in patient load.
State Additional Director (Public Health) Dr Nilam Patel said, “We have set up 20,000 teams comprising two people each that are going house-to-house checking for water sites.”

“Water chlorination levels are being checked, chlorine tablets distributed and pipeline repairs are being recommended where required… Our teams have also started putting Temefos solution in stagnant water and de-watering teams are working to dry out waterlogged areas. A health survey is also being carried out simultaneously,” she added.

Temefos or temephos is an organophosphate larvicide used to treat water infested with disease-carrying insects like
mosquitoes.

Research conducted on dengue virus in circulation in Gujarat earlier this year has found that it was Serotype DENV-I and not the severe strain that was seen in 2021. Patel said that in Vadodara, the city most affected by the recent flooding, the municipal corporation had tested samples from 1,500 mosquitoes, but no trace of dengue haemorrhagic fever was found.

Asked about the possibility of sandflies – the vector causing Chandipura Vesiculovirus mostly among children in Gujarat – also breeding again, Patel said their breeding sites would have been wiped out by the recent rain.

A health worker said they have found mosquito breeding spots in the cleanest of homes, even in two-inch ornamental decorations. “A coconut shell filled with water can also become a breeding spot for 1,000 mosquito larvae,” said Patel.

Officials warned of potential breeding sites in plain sight, such as bird feeders filled with water, outdoor decorations, plant pots, terrace gardens and basement parking lots. Also, civic workers said they face the most problems in urban areas. “People don’t easily allow our workers to enter their homes, especially the affluent, even as their houses have the most breeding spots,” an official said.