Will warm weather really kill off Covid-19?
Could the severity of the new coronavirus (COVID-19), or its ability to spread, be less severe as temperatures warm-up? This question has been spread from places to places, from countries to countries. However, "pandemics often don’t behave in the same way as seasonal outbreaks", according to the BBC (2020).
Many infectious diseases wax and wane with the seasons. It is said that flu typically arrives with the colder winter months, as does the norovirus vomiting bug. Many people are now asking whether we can expect similar seasonality with Covid-19. Since it first emerged in China around mid-December, the virus has spread quickly, with the number of cases now rising most sharply in Europe and the US.
There are some clues from other coronaviruses that infect humans as to whether Covid-19 might eventually become seasonal.
A study conducted by Kate Templeton, from the Centre for Infectious Diseases at the University of Edinburgh, UK, found that three coronaviruses – all obtained from patients with respiratory tract infections at hospitals and GP surgeries in Edinburgh – showed “marked winter seasonality”.
These viruses seemed to cause infections mainly between December and April – a similar pattern to that seen with influenza. There are some early hints that Covid-19 may also vary with the seasons. The spread of the Covid-19 outbreak around the world seems to suggest it has a preference for cool and dry conditions.
An unpublished study has also shown higher temperatures are linked to lower incidence of Covid-19 but notes that temperature alone cannot account for the global variation in incidence. Further as-yet-unpublished research predicts that temperate warm and cold climates are the most vulnerable to the current Covid-19 outbreak, followed by arid regions. Tropical parts of the world are likely to be least affected, the researchers say.
The weather can also mess with our immune systems to make us more vulnerable to infections, too. There is some evidence to suggest vitamin D levels in our bodies can have an effect on how vulnerable we are to infectious diseases. In the winter our bodies make less vitamin D from sunlight exposure, mainly because we spend more time indoors and wrap ourselves in clothing against the cold air.
However, more controversial is whether cold weather weakens our immune systems – some studies suggest it does, but others find the cold can boost the number of cells that defend our bodies from infection.
Sayings vary. "There’s no evidence yet for a seasonal behavior of Covid-19,” says Vittoria Colizza, Director of research at the French Institute of Health and Medical Research. “The behavioral component may play a role, too.” But she warns it is too early to know if the measures put in place will be enough to stall the spread of the virus. “By itself, it may partially reduce effective contagiousness due to the reduction of contacts along which the disease could be transmitted.”
Even if Covid-19 does show some seasonal variability, it is unlikely to disappear entirely over the summer months, as some have suggested. But a dip in cases might bring some benefits.
“The steps we are taking to flatten out the curve are expensive in economic terms, but they could help us push this pandemic into the summer”. “If there is some seasonality, it might buy health systems the time they need to prepare.”, says an expert.
And in a world scrambling to cope with the rapidly rising number of cases, it might just be time we desperately need.
Source: Richard Gray, BBC