For months people have been hoping that coronavirus will go away in the summer and key public figures have voiced their hopes for it to go away too, while many news organisations have called it a ‘myth’. Pakistani Prime Minister Imran Khan has said that Pakistan’s “hot and dry weather” will mitigate COVID-19 for which he received plenty of flak from the media and some experts, but is his claim true or just a ploy to reduce panic and induce calm?
Research
As of now, there are not enough studies to determine a clear and concise answer to the possibility of SARS-CoV-2’s seasonality, but the limited researched performed has shown promising results that COVID-19 could slow down in warmer surroundings. At room temperature (20°C to 25°C) with an average humidity of 50%, COVID-19 can survive for around four days on common solid surfaces and for 3 to 9 hours in air; a study performed by Healthcare Infection Society found that SARS-CoV-2 can survive for up to 28 days on common surfaces if the temperature of surroundings is 4°C. Moreover, research performed by University of Maryland showed that most areas where COVID-19 has spread rapidly have experienced average temperatures of 5°C to 11°C and low humidity (less than 30%). Furthermore, research published by medRxiv which analysed the spread of COVID-19 around the globe suggested that areas with higher temperatures, humidity and wind speeds tend to have lower incidence of COVID-19.
On the contrary, a study published by Harvard Medical School which analysed the spread of SARS-CoV-2 in Asia found that higher temperatures and humidity seem to have a negligible impact on the spread of the virus, and that the contagion of the disease is rather highly dependent on public health programs and efforts – especially social distancing.
The geographic results as of now
Proponents of the argument that COVID-19 is non-seasonal often cite that places experiencing summer or hotter weather such as South East Asia and the Southern Hemisphere have observed rapid spread of SARS-CoV-2 and many of them are hotspots.
South East Asian countries are known to have tropical weather (hot and humid) throughout the year and many of them including Singapore, Malaysia and Indonesia have suffered severely from the pandemic. However, experts cite that frequent travel of natives from these countries to China especially during Chinese New Year and irresponsible large gatherings such as the 16000-person Islamic Conference in Malaysia have caused massive clusters in South East Asian countries. As for countries in the Southern Hemisphere, they were transitioning away from summer weather and were not experiencing extreme/peak hot weather that could have massively limited the spread of the disease.
Previous pandemics
Normal outbreaks of novel diseases and viruses tend to be seasonal, but pandemics appear to not show the same seasonality. The Spanish Flu which killed between 50 to 100 million surprised experts in 1918 when it peaked during the summer season, although the consensus back then (and still is) was that flu outbreaks peak during the winters. History of pandemics tells us that diseases that become pandemics are not certain to be seasonal.
Other coronaviruses
Till now, only seven human-infecting coronaviruses have been discovered out of which four appear to be highly seasonal and spread like influenza. They migrate to the Southern Hemisphere in the summers and come back during the winters.
The SARS outbreak began in the winter of 2002, slowed down in the summers of 2003 and 2004 and returned during the winters of both years – even though SARS is not considered to be seasonal since there have been no reported cases since 2004. On the other hand, MERS’ initial outbreak peaked in the summer weather and it continues to exist all year round in the Middle East on a small scale. Since, the genetic material of COVID-19 is most similar to SARS (80% to 90% similarity), scientists estimate that COVID-19’s spread could very well be lessened in the summers but a second wave in the winters would be highly likely.
Expert predictions
Coronaviruses are known to be ‘enveloped’ viruses meaning they are coated with an oily layer filled with proteins that stick out like corona (crown). Enveloped viruses are less resistant to heat and in colder surroundings form a rubber-like oily layer which allows them to survive for extended periods of time. Based on this information, scientists believe that the R0 (the number of expected cases directly caused by one infected person) of SARS-CoV-2 would significantly fall during the summers.
Additionally, people tend to stay indoors during the winters (offices or homes) causing people to be in close proximity of each other. During summers, people are more spread out and a greater distance is maintained between one person to the next, so the spread of the disease is lessened. Plus, if someone sneezes or cough in the open during the summers, the high temperatures kill pathogens in air within seconds which makes it difficult for others to get infected. To add on, during the winters, approximately 30% of the public faces vitamin D deficiency due to a lack of sunlight exposure thus weakening the immune system – a key reason for why flu is prevalent during the winter season. On top of that, when the air is less humid during the winters, mucus in the human lungs and respiratory system decreases. Mucus is an important substance that naturally defends the immune system against infections by stopping pathogens from going deeper into the respiratory system. A loss or decreased amount of mucus in the lungs has been linked to higher incidences of infection.
For these reasons, many experts believe that the summer weather will significantly decrease the number of COVID-19 related cases and deaths, and possibly bring the outbreak to an end for a little while.
Outlook
Scientific research and rationale do imply that SARS-CoV-2 could be seasonal and that the spread of the disease could be limited or reduced in hot and humid climates – but it is unlikely to go away altogether in the summer. However, scientists have warned of a deadlier second wave in the winters as populations in most regions and countries do not have widespread immunity yet – for a society to be considered immune, more than 80% of the population must have already been infected by the disease. Since a vaccine is still more than 12 months away, health experts are urging governments to develop better public health and pandemic responses/systems in the summer season so that a winter outbreak of SARS-CoV-2 can be prevented.
Imran Khan’s claims of the Pakistani weather diminishing the impact of COVID-19 are valid but that does not let his administration and government off the hook. The Pakistani government needs to be prepared for future health crises and use the valuable time in the summers to stock up on key medical supplies such as ventilators, PPE and ICU units, and find ways to deal with shortages of skilled medical staff.
