Growing evidence for COVID-19 being seasonal, thrives better in wintertime conditions: WMO

Link emerging between long-term exposure to air pollution and severe COVID-19 infection can be bad for India, WMO study

By Taran Deol
Published: Friday 24 June 2022
Growing evidence for COVID-19 being seasonal, thrives better in wintertime conditions: WMO Photo: iStock

There is growing evidence to suggest COVID-19 pandemic is seasonal and the virus thrives better in winter conditions in temperate regions, according to the World Meteorological Organization.

This trait has been recorded in other respiratory illnesses as well, including influenza and other human coronaviruses, according to the latest update from the WMO COVID-19 task team.

A contributing factor to this trend is a greater concentration of people in poorly ventilated indoor areas, it said.

The update released on June 22, 2022 underscored that “one cannot assume reduction in risk during warm seasons, as other factors can dominate the seasonal influence on overall risk profiles”.

This prediction is right despite India experiencing a deadly second wave of the pandemic during the summer months of April, May and June in 2021, according to experts. 

Gagandeep Kang, virologist with the Christian Medical College-Vellore, told Down To Earth:

When a virus is newly introduced, it will not be immediately seasonal. There will be large oscillations before it settles into a pattern. So yes, the prediction that this will behave like other respiratory viruses is not surprising.

While temperature and relative humidity play a role, they are only contributing factors, argued Rajeev Jayadevan, co-chairman of the Indian Medical Association’s COVID-19 National Task Force. 

COVID-19 has a cyclic pattern and not a seasonal one, he added. “It is driven by continuously adapting to escaping immunity and faster transmission, which leads to emergence of fitter variants. These do not occur according to season, but by opportunity.” 

Air pollution link

Long-term exposure to air pollutants, including particulate matter, ozone and nitrogen dioxide, is associated with more severe COVID-19 symptoms and higher likelihood of death, WMO noted citing epidemiological studies. 

“Evidence regarding the influence of short-term air pollution exposure to COVID-19 risk is still emerging,” the United Nations agency added. 

This could be especially bad news for India, whose capital is the most polluted city in the world, it added. Some 63 Indian cities feature in the top 100 most polluted cities in the world, according to a report prepared by the Swiss firm IQAir. 

Indians are already losing five years of their life expectancy due to air pollution and the figure is double for the residents of Delhi, according to a new analysis by the University of Chicago.

These figures are from the India factsheet released by the university’s Energy Policy Institute’s Air Quality Life Index this month. It noted that these figures were “relative to what (the life expectancy) would be if the World Health Organization guideline regarding fine particulate pollution (PM2.5) of 5 microgram per cubic metre was met.”

The WMO update also detailed the link between COVID-19 and compound hazards. These “are events where more than one hazard interacts and cause multiplicatively destructive consequences,” Yale School of the Environment noted. 

Such events are on the rise due to climate change, said the latest Intergovernmental Panel on Climate Change report. 

“The COVID-19 pandemic combined with weather and climate risks to create multiple major compound hazard events that challenged local authorities to adhere to disease prevention protocols, while managing extreme weather events,” the WMO report said.

The global body recommended documenting datasets in a timely manner and piecing together a framework for risk assessment. “The scramble for data and information exchange at the outset of the pandemic emphasises the need to establish long-term collaboration between the weather, climate and environmental services and public health communities, including academics, practitioners, policymakers and funders.”

There should be clear corresponding roles and ownership to support critical public health research and response, it added. 

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