New Delhi: Delhi’s peak summer has come accompanied with a surge in the number of coronavirus cases, but experts and trends both suggest it is coincidental and not causal.
Delhi recorded an average daily case total of 65 in the first week of April, the first summer month, according to government health bulletins. However, the number has surpassed 1,000 fresh cases daily almost every day since May-end. On Friday, the national capital reported over 2,000 fresh cases in a day.
However, the temperature trends appear to suggest the link is a coincidence.
Even though the first six days of June 2020 were the coldest in nine years, with temperatures staying below 40 degrees Celsius, Delhi’s coronavirus cases continued to surge. On 3 June, the total number of coronavirus cases in Delhi stood at 22,132, which reached 25,004 on 5 June.
Since 8 June, Delhi has recorded temperatures of above 40 degrees Celsius — 44 degrees on 10 June, 42 degrees on 11 June and 41 degrees on 15 June. While the number of coronavirus cases in the capital was recorded at 31,309 on 10 June, it was 38,958 on 13 June and 41,182 on 15 June.
Experts offer a similar assessment.
‘Anecdotal and speculative’
There has been no study so far that has conclusively proved that temperature has a direct impact on the transmission of SARS-CoV-2, the virus that causes Covid-19, even though the prospect has been a subject of much speculation.
“Since the global spread of Covid-19, several theories continued to float around relating climatic predictors to the virus’ behaviours, a majority of which were anecdotal and speculative,” said Dr Tanmay Mahapatra, a public health expert and an epidemiologist working with CARE India, a non-profit that is supporting Bihar in its Covid-19 efforts.
According to Mahapatra, the increase “in the number of cases during high temperatures is more coincidental than causal”.
Giridhar R. Babu, professor and head, lifecourse epidemiology, at the Public Health Foundation of India, a government-private collaboration, agreed. “There no association proved between the temperature and the disease spread. We can’t make inferences with rising temperatures. This is a random variable as of now.”
He added, “This sudden increase in coronavirus cases in Delhi is natural progression of the pandemic. In any city, the increasing number is only because of increasing mobility and increased testing.”
Mahapatra said seasonality will be a coincidence, adding that there are other “speculated sources of variations such as sensitivity and specificity of tests, strict or relaxed implementation of lockdown, health infrastructure, changes in response of health systems etc”.
“We have to keep these additional variations in mind before directly correlating any such factors with the epidemic growth curve as we are seeing the reported cases and predicting through statistical models,” he added.