Explained: Will monsoon impact the spread of Covid-19?

Mosoon impact on Covid-19: The effort is to look for clues in the way other similar viruses behave during the rainy season.

Explained: Will the monsoon impact the spread of COVID-19?

In Thane on June 13, 2010. The southwest monsoon covered Maharashtra this week. (Express Photo: Deepak Joshi)

Some months ago, when the novel coronavirus epidemic was still emerging in India, it was hoped that rising temperature in the summer months would weaken the potency of the virus and slow down its spread. That did not happen. Now that the monsoon season is here, the likely impact of rain on the virus, and its transmission, is the subject of discussion.

Since it is a new virus, scientists are not yet sure how the rain might affect its behaviour. So the effort is to look for clues in the way other similar viruses behave during the rainy season.

Much still unknown

Rain brings with it several vector borne diseases like malaria, dengue and chikungunya. In the case of dengue, some studies have shown that excessive rains could disrupt the mosquito’s reproductive cycle and flush out its breeding sites.

But the comparison that is being made is that with influenza, which, like Covid-19, is a respiratory disease, though there are important differences in the way the two viruses replicate and affect human beings.

The problem, as Dr Marc-Alain Widdowson, an infectious disease epidemiologist who worked with US Centers for Disease Prevention and Control and is now Director of the Institute of Tropical Medicine, Antwerp, Belgium, points out, is that even in the case of influenza, and several other viral respiratory diseases, the drivers for their seasonal behaviour are not fully understood.

“In the United States, for example, it is very difficult to predict the flu season. There is no single factor like temperature or rainfall, or staying indoors that can be said to have decisive impact. Many other factors like sunlight, and Vitamin D levels in people are also responsible in how these diseases spread. In addition, it is not very clear how much transmission happens through surfaces (as against human contact, or through air). Most people are of the opinion that only little contamination happens through surfaces. And, that during the rainy season, it would not affect indoor surfaces at all,” he said in an email.

Dr M S Chadha, former Deputy Director of National Institute of Virology who has worked on the seasonality of the respiratory synctial virus (RSV), said it could take several years to determine how novel coronavirus is affected by different seasons. “Since RSV infection and other respiratory diseases usually do follow seasonal patterns, carrying out year-round Covid-19 surveillance for several years would be the key to determining its seasonality,” he said.

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Seasons & human behaviour

Dr Subhojit Sen, a scientist with Centre for Excellence in Basic Sciences in Mumbai, said the viral disease spread depends on three major factors — seasonal changes in environment (temperature, humidity, sunlight), human behavioural patterns, and intrinsic characteristics of the virus, like its infectiousness, pathogenicity and survival.

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He pointed out some of the things that can be expected during the rainy season that can have an impact on how such diseases spread.

“For example, spitting on the streets is a common problem that increases the risk of virus transmission. The hope is that rains will wash or dilute this off the streets,” he said. Also, during rains, people spend an extended period of time within closed spaces, like homes or offices, and there is likely to be a lower number of people in crowded public spaces.

Anuradha Mascarenhas

Anuradha Mascarenhas is a Senior Editor at The Indian Express, based in Pune. With a career spanning three decades, she is one of the most respected voices in Indian journalism regarding healthcare, science and environment and research developments. She also takes a keen interest in covering women's issues . Professional Background Education: A gold medalist in Communication and Journalism from Savitribai Phule Pune University and a Master’s degree in Literature. Author: She authored the biography At The Wheel Of Research, which chronicles the life and work of Dr. Soumya Swaminathan, the former Chief Scientist at the WHO. Key Focus: She combines scientific accuracy with storytelling, translating complex medical research into compelling public and human-interest narratives. Awards and Recognition Anuradha has won several awards including the Press Council of India's national award for excellence in journalism under the gender based reporting category in 2019 and the Laadli Media award (gender sensitivity -2024). A recipient of the Lokmat journalism award (gender category-2022), she was also shortlisted for the RedInk awards for excellence in journalism-2021. Her debut book At The Wheel Of Research, an exclusive biography of Dr Soumya Swaminathan the inaugural chief scientist of World Health Organisation was also nominated in the Popular Choice Category of JK Paper AUTHER awards. She has also secured competitive fellowships including the Laadli Media Fellowship (2022), the Survivors Against TB – New Research in TB Media Fellowship (2023) and is part of the prestigious 2025 India Cohort of the WomenLift Health Leadership Journey.” Recent Notable Articles (Late 2025) 1. Cancer & Specialized Medical Care "Tata Memorial finds way to kill drug-resistant cancer cells" (Nov 26, 2025): Reporting on a breakthrough for triple-negative breast cancer, one of the most aggressive forms of the disease. Discipline, diet and purpose; How a 97-year-old professor defies ageing'' (Nov 15, 2025) Report about Prof Gururaj Mutalik, the first Head of Department at Pune's B J Government Medical College who at 97 credits his longevity to healthy habits and a strong sense of purpose. 2. Environmental Health (The "Breathless Pune" Series) Long-term exposure even to 'moderate' air leads to chronic heart, lung, kidney issues" (Nov 26, 2025): Part of an investigative series highlighting that even "safe" pollution levels are damaging to vital organs. "For every 10 µg/m3 increase in PM2.5 level, there was 6-8% jump in medicine sales" (Nov 23, 2025): Using commercial data to prove the direct link between air quality and respiratory illnesses in Pune. 3. Lifestyle & Wellness News "They didn't let cancer, diabetes and heart disease stop them from travelling" (Dec 22, 2025): A collaborative piece featuring survivors who share practical tips for traveling with chronic conditions. At 17, his BP shot up to 200/120 mmHG; Lancet study flags why child and teen hypertension doubled between 2000 and 2020'' (Nov 12,2025)--A report that focusses on 17-year-old-boy's hypertensive crisis and reflects the rising global trend of high blood pressure among children and adolescents. 4. Scientific Recognition & Infrastructure For promoting sci-comm, gender diversity: IUCAA woman prof highlighted in Nature" (Nov 25, 2025): Covering the global recognition of Indian women scientists in gender studies and physics. Pune researchers find a spiral galaxy like the Milky Way from early universe'' (December 3, 2025)- A report on how Indian researchers discovered a massive galaxy that existed when the universe was just 1.5 billion years old , one of the earliest to have been observed so far. Signature Beat: Health, Science & Women in Leadership Anuradha is known for her COVID-19 reportage, where she was one of the first journalists to provide detailed insights into the Covishield and Covaxin trials. She has a dedicated interest in gender diversity in health and science, often profiling women researchers who are breaking the "leaky pipeline" in STEM fields. Her writing style is scrupulous, often featuring interviews with top-tier scientists and health experts from various institutions. ... Read More