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Infectious Diseases

16 March 2020

Will warmer weather really help deter the coronavirus?

As we are not yet in our Southern Hemisphere winter, it’s hard to tell how many people will still get ill. But experts are not so sure if warmer temperatures make that big a difference.

As the new coronavirus rapidly spreads around the world, scientists are still trying to figure out how exactly this virus will affect us.

A hot topic is whether climate and weather play a part in the spreading of the disease.

Surely it’s simply too hot in South Africa right now, and surely we can contain an outbreak before winter hits us?

Will the pandemic start flat-lining in the Northern Hemisphere as their spring arrives? Is the panic really necessary – isn’t it just flu after all?

Experts are hoping for the former – that the virus will start tapering off in spring, just like seasonal influenza. Nelson Michael, a leading US military medical researcher, said to CNN World: “This is a respiratory virus and they always give us trouble during cold weather, for obvious reasons. We are all inside, the windows are closed etc., so we typically call that the influenza or the flu season.”

We know that seasonal influenza tends to thrive in colder, drier conditions, hence the reason why people are hoping that the new coronavirus behaves like seasonal influenza. But is this new strain of virus climate sensitive?

What the evidence says

While there is some evidence to suggest that the coronavirus thrives in certain climates, it’s not enough to reach a definite conclusion.

A new study was published last week. In this research, a team from the University of Maryland and the University of Medical Sciences in Tehran used weather modelling to determine which regions were most likely to be at a high risk of transmission of the new coronavirus.

The study suggested that the ideal region would be between five and 11 degrees Celsius, with a humidity of between 50% and 80%.

This, however, doesn’t necessarily mean that warmer regions are less at risk of a severe outbreak.

Marc Lipssitch, an epidemiologist from Harvard, wrote that warmer weather is simply not enough to slow down the transmission of the virus. 

"New viruses have a temporary but important advantage – few or no individuals in the population are immune to them. Old viruses, which have been among the population for longer, operate on a thinner margin – most individuals are immune, and they have to make do with transmitting among the few who aren’t. In simple terms, viruses that have been around for a long time can make a living – spread through the population – only when the conditions are most favourable, in this case in winter," he stated.

This means that new pandemic viruses are not affected by seasonality.

Is warmer weather generally better for health?

Even though we shouldn’t cling to the reassurance of temperature, it seems that spring and summer change the behaviour and thus the rate of transmission of a new virus.

When experts compare this new coronavirus to the virus that caused the SARS outbreak in 2003, there are similarities – this outbreak also started in the winter of the Northern Hemisphere and tapered off in July 2003.

David Cennimo, who studies infectious diseases at Rutgers New Jersey Medical School, was quoted on CNN, saying that many experts "hope – and I think the correct word is hope – that the summer will push down the case numbers". He, however, added that "the data from tropical countries may rain on this hope somewhat".

While we remain unsure about the extent of the situation in South Africa, there is at least the good news that outbreaks in two of the countries that were initially worst hit, China and South Korea, are tapering off.

In the meantime, the best way to protect yourself is to limit travel to current high-risk areas, to wash your hands regularly and to avoid close contact with those who have travelled to high-risk areas. 

Image credit: CDC, Unsplash