Stubble burning is intentionally setting fire to the straw stubble that remains after grains, like paddy, wheat, etc, have been harvested.

India’s achievement of reducing its daily Covid-19 case count to the lowest in two months could be negated, especially in the north and the National Capital Region of Delhi, as thick winter fog becomes heavier due to rising air pollution from the burning of post-harvest stubble, increasing the likelihood of transmission.

Delhi has been among the world’s most polluted cities over the past five years due to emissions from industry, automobiles and power plants. While some of those emissions have been reduced, stubble burning continues on the same scale, affecting air quality across the entire northern region.

The northern states of Punjab, Haryana and Uttar Pradesh produce the bulk of India’s rice and wheat crops, according to the New Delhi-based Centre for Science and Environment, and the burning of paddy stubble in October and November can affect the air quality hundreds of kilometres away.

Delhi on Tuesday recorded an Air Quality Index (AQI) of 300, with particulate matter or PM2.5 and PM10 as the most prominent pollutants. An AQI of 301 to 400 is categorized as “very poor.” It can cause respiratory illness after prolonged exposure. Delhi residents, who are complaining of burning eyes, are concerned about how the pollution will affect them over the next four months.

State leaders are squabbling with both each other and the central government about how to address the enduring problem.

“Pollution plus coronavirus has become lethal for people,’’ said Manish Sisodia, the deputy chief minister of Delhi, on Tuesday, accusing the central government of failing to play an active role in solving the problem.

With cropping cycles getting shorter, mechanization increasing, and the market for crop residue shrinking, farmers find it cheaper and easier to burn the stubble post-harvest. Smoke from these burning stalks usually hangs in the winter air for a long time, often holding up rail and road traffic, especially around dawn and dusk.

“A positive correlation has been observed between the spread of the virus and air pollution, one of the greatest challenges of our millennium,’’ according to the US-based National Center for Biotechnology Information (NCBI).

“Covid-19 atmospheric particulate matter (PM) could create a suitable environment for transporting the virus at greater distances,’’ said the NCBI study. “PM induces inflammation in lung cells and exposure to PM could increase the susceptibility and severity of the Covid-19 patient symptoms.”

India’s health minister has also been warning about the increased flu and influenza risk during the winter. Dr Harsh Vardhan on Tuesday appealed to the public to be extra careful during the upcoming festival season and the winter months, when there is expected to be an increase in cases of co-infection with Covid-19.

The main Hindu festivals begin on October 18 with Navaratri, or nine-nights, and Durga Pooja, when people get together for prayers, and in some states there are community dances, too. The season culminates with Diwali on November 14. A typical family makes its annual purchases of clothes and household items at this time.

States relaxing lockdown restrictions are in a bind, caught between the objective of saving lives and yet not being seen as obstructing religious activities. Maharashtra and its capital Mumbai have not permitted visits to places of worship, even while opening restaurants and cinemas. Delhi has relaxed its restrictions more, including opening up temples and other places of worship.

Most experts and doctors in India have warned about about the possibility of an upsurge in the number of cases. Some predict India will surpass the United States to have the most number of Covid cases before the end of the year. With 7.2 million cases, India is second to the US’s eight million. In third place is Brazil with 5.1 million. The three countries account for more than half the 38 million cases globally.

To the credit of India’s corona-warriors, the country has recorded 6.2 million recoveries, the highest number globally, ahead of 5.2 million in the US. The number of cases described as active or undergoing treatment has remained below 900,000 for the fifth consecutive day, the Health Ministry said Tuesday.

India has the highest recovery rate – 86.78% – and among the lowest fatality rates – 1.53%, it said. The number of days it takes for the number of cases to double has increased to 74.9 days.

India is witnessing a steady decline in its average daily positivity rate, Rajesh Bhushan, India’s health secretary, said. Over the last several months India has ramped up its testing program and is now conducting 1.5 million tests a day. In all, it has conducted 89 million tests, behind the US’s 119 million and China’s 160 million.

India has recorded a consistent decline in the average number of daily new cases over the past five weeks, from 92,800 cases in the week ending September 15 to less than 70,000 daily cases in the week ending October 15, the ministry said. Of 109,923 deaths, 70% were men. More than 53% of fatalities were people aged 60 or over. About 35% of fatalities were in the 35-60 age group.