Air pollution may increase transmissibility of the novel coronavirus making people more vulnerable to the disease and aggravating the COVID-19 situation, experts have said, while warning that those who have had the infection in the past may also have to face new challenges.

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With winters approaching and easing of the coronavirus-induced lockdown, Delhi-NCR is bracing for months of poor air quality. The national capital's air quality was in the 'poor' category on October 18 morning. According to doctors, respiratory illnesses like viral influenza increase with a spike in pollution levels as poor air quality leads to inflammation in the lungs making it more vulnerable for the virus to penetrate. "This year, we have COVID-19. Like the common cold, the transmission of this virus is expected to increase with a rise in pollution levels. We may see a further surge in cases. "It would be a taxing time for testing centres as they have to cater to people with coronavirus and also non-COVID patients with similar symptoms," Dr Neeraj Nischal, an associate professor in the Department of Medicine at AIIMS, told PTI.

Experts feel the worst-affected would be people in the lower socioeconomic class with no access to masks and also vulnerable to additional risk factors such as chulla smoke. "Transmission apart, the presentation of COVID-19 like other viral respiratory illnesses will be more severe in high-pollution areas. This will burden hospitals as more patients become symptomatic, requiring admission," Dr Nischal said. According to Dr Neeraj Gupta, a professor in the Department of Pulmonary, Critical care and Sleep medicine at Safdarjung Hospital, mortality has been linked with population density, the proximity of people and heavily industrialized or urbanised areas which have higher pollution levels.

These factors are likely to become more effective during the festive season and winters, particularly in north India where stubble burning is common and this affects air quality severely, he said. "Italy showed a possible link between PM 2.5 concentration and excess mortality to the extent that one unit increase is associated with a 9 percent increase in COVID-19 mortality," Dr Gupta said, adding pollution can also assist in the transmission of the novel coronavirus. During smog, particulate matters remain suspended in the air near the earth's surface for a longer period making it conducive for the transmission of the virus, he elaborated.

Dr Suranjit Chatterjee, senior consultant of Internal Medicine at Apollo Hospitals, said, "We really don't know how this virus is going to behave. But, we need to prepare ourselves for the worst, as pollution level increases and with winter setting in. It will be a dangerous combination." He cautioned that people with respiratory illness, like asthma and bronchitis, were at much higher risk of contracting coronavirus infection. "For people who have tested positive for COVID-19, it is going to be a double whammy, with pollution making things worse," he told PTI.

Doctors warn that even those who have had COVID-19 in the past are not out of the woods. "Post-COVID fibrosis and immunoparalysis make their lungs more susceptible to super-added bacterial pneumonia and other viral respiratory illnesses. We urge everyone to get inoculated with the influenza vaccine and pneumococcal vaccine to prevent additional infections in these times," Dr Nischal stressed. According to Dr Gupta, with the cohort of survivors of COVID-19 increasing, a significant number is noted to be symptomatic -- 43 percent with respiratory complaints-- even after two months.

These individuals are particularly vulnerable to air pollution, which is known to cause chronic airway irritation and inflammation, affects mucus clearing, impairs immunity and acutely precipitates airway disorders like asthma, COPD, lung fibrosis or even cancer-related conditions. "Indeed, a tough time for post-COVID patients is in store," Gupta added.

Dr Vivek Nangia, principal director and head of pulmonology, Max Super Speciality Hospital in Delhi's Saket said that for individuals belonging to the high-risk groups who are at extremes of ages and suffering from chronic disease are advised to stay indoors or at least restrict their movement to bare essential activities outdoors. "While outdoors, wear a mask at all times and stay away from firecrackers during Diwali. Keep inhaler handy and consult a doctor at the earliest. Even for the others, it is strongly recommended that they minimize their outdoor activities and wear a mask at all time," he said. "The number of cases will go up. There is a study which has been published by Harvard Medical School, USA, where they have shown that with every 1 micron per metre rise in PM 2.5 particles, there's an 8 percent increase in the mortality," he said.

India's COVID-19 caseload mounted to 74,94,551 with 61,871 new infections being reported in a day, while the number of recoveries surged to 65,97,209 pushing the recovery rate to 88.03 percent, according to the Health Ministry data updated on October 18 morning. The death toll climbed to 1,14,031 with the virus claiming 1,033 lives during the same period.