Flu season stretches on as excess rain delays the onset of summer
NEW DELHI: India received 117% excess rain in the first 14 days of March, with 71% of the subdivisional area — India has 36 meteorological subdivisions — experiencing “large excess” (60% above normal) precipitation. In the northwestern region, all nine states have recorded large excess rains, 150% above normal.
The unusually wet weather, and the colder temperatures it has brought, have proved to be a dampener for hopes that the onset of warmer days would stem the tide of the novel coronavirus and reduce its incidence although virologists say there’s no evidence yet of that being the case.
Because of several episodes of rains and thundershowers this month, most parts of north India also recorded maximum temperatures that were 3 to 4 degrees Celsius below normal.
The last time March received such unusually high rainfall was in 2015, when rainfall was 99% excess for the entire month. Before that, in 1990, total rainfall in March for the entire country was 79% in excess. In February this year, rains were 48% deficient. The rain in March received by Delhi is an all-time record. Untill March 14, Safdarjung recorded 101.9 mm of rainfall, beating the 97.4mm recorded in the same month in 2015.
“There have been back-toback western disturbances which brought rain to the northern plains. Usually western disturbances move to the northern latitudes in March but this year they have continued to impact the plains,” said Mahesh Palawat, vice president, climate change and meteorology at Skymet Weather, a weather forecaster.
“There is also moisture feed from the Arabian Sea, leading to most of northwest India recording 3 to 4 degree C below normal maximum temperatures. In Delhi, maximum temperature has been 1 to 7 degrees C below normal between March 6 to 13. Parts of Bihar, Uttar Pradesh, east Madhya Pradesh and Chhattisgarh are also recording below normal temperatures,” Palawat said. “Temperatures have been lower than normal in most of north India because of the three western disturbances on March 1, from March 4 to 7 and the one that has hit north India since March 10,” said Kuldeep Shrivastava, head of the Regional Weather Forecasting Centre.
“Another western disturbance is expected around March 14-15 but it will be a milder one affecting mostly the hills,” said Shrivastava, adding that the ongoing western disturbance had caused widespread hailstorms in parts of Delhi, Rajasthan, Haryana and Uttar Pradesh on Friday and Saturday.
Below-normal temperatures have meant more conducive conditions for influenza illnesses but towards the end of the month, maximum temperatures are likely to hit 30 to 32 degree C, bringing some relief, said Palawat. He quoted a study by the Institute of Virology, University of Maryland School of Medicine which found that the new coronavirus, or Covid-19, had established significant community spread in cities and regions only along a narrow east -west distribution roughly along the 30-50 N corridor at consistently similar weather patterns (5-11 degree C and 47-79% humidity).
What it means is that community transmission was seen in countries located around the same latitude coordinates and with similar temperature and humidity patterns.
The study, published in the Social Science Research Network journal on March 9 , concludes that using weather modelling; it may be possible to predict which regions are most likely to be at a higher risk of significant community spread of Covid-19 in the coming weeks, allowing for concentration of public health efforts on surveillance and containment. New areas with significant community transmission include the northwestern United States and France. During the same time, Covid-19 failed to spread significantly to countries immediately south of China, the study noted. The number of patients and reported deaths in Southeast Asia is much less compared to temperate regions but the study cautioned long-term prediction cannot be made immediately.
“There i s a definite l i nk between temperatures, humidity and Covid-19 but we can tell only once it gets warmer here,” added Palawat. “The region affected they are referring to in the study is also called the subtropical high. Westerlies are common in that area and there is a lot of subsidence (descending motion of air). The region is mainly dry and has cold nights,” said DS Pai, senior scientist at the India Meteorological Department (IMD).
“We are expecting below normal temperatures till March 20 in many parts of India because of western disturbances but after that temperature will gradually increase,” he added.
But virologists say there is no evidence yet that Covid-19 infections will come down in the summer. “Apart from the fact that the virus causing Sars {Severe Acute Respiratory Syndrome} and Covid-19 belong to the same family of beta coronavirus and use the same receptor to infect humans, there is not much in common. Covid-19 does not have as high a mortality rate as Sars but is highly infectious – almost as much as the most infectious measles and chicken pox. So, we cannot infer anything about Covid-19 from how Sars spread,” said Dr Shobha Broor, former head of the department of microbiology at the All India Institute of Medical Sciences in New Delhi.
“The rise in ambient temperature might not have any effect in stopping the virus. It may reduce the transmitability – when the temperature of various surfaces go up, the virus might survive for less time on it, thus infecting fewer people. It is an enveloped virus that gets killed at higher temperatures. Since it is not transmitted by aerosols in the environment, rising ambient temperatures do not help,” said Dr Broor.