Does the weather play a role in containing a viral outbreak? This correlation has been broached and debated upon for many years, even during the outbreak of 2003 Severe Acute Respiratory Syndrome (SARS) and 2012 Middle East Respiratory Syndrome (MERS), both caused by coronaviruses (CoV).
The debate has now come to the fore, once again, as the number of deaths and suspected cases of novel coronavirus or COVID-19 has globally touched 3,198 and 93,453 respectively. In fact, US President Donald Trump’s statement or “theory” about the outbreak — "In April, when it gets warm... historically, that has been able to kill the virus" — has many wondering if summer or meteorological factors can impact or contain the viral outbreak.
Global health experts are still studying the characteristics of the new respiratory virus as it is caused by a previously unindentified strain of coronavirus, which is now being termed SARS-CoV-2. Hence, while there is no definitive answer on whether warm and humid weather conditions in a country like India can control its spread, here’s what some health experts note.
COVID-19 spreads through the suspension of virus-containing sneeze, cough and other droplets in the air, especially if the healthy person is standing within six feet or one meter of an infected person.
Elizabeth McGraw, director of the Center for Infectious Disease Dynamics (CIDD) at Pennsylvania State University, told Time that the virus in droplets do not stay suspended in the humid air for a long time, and that the warmer temperatures can cause rapid degradation of the virus.
This also brings focus to the geography or seasonal patterns of the virus outbreak. For example, according to US-based The Weather Channel, in China’s Wuhan city, which is the epicentre of the COVID-19 outbreak, the maximum number of cases were reported between late December 2019 and February 2020. During these months, the city experienced sub-zero minimum (below freezing point) temperature — that is, below zero degree Celsius or 32 degrees Fahrenheit.
Similarly, South Korea’s Seoul also saw a spike in confirmed cases when the minimum temperature was below zero degree Celsius — an average lower temperature of minus 7 degree Celsius (or 19 degrees F). According to the report, Rome, Italy and Tehran, too, recorded sub-zero temperatures in February.
Incidentally, a study on ‘the impact of weather on primary cases of MERS’ suggested that the lowest temperature and humidity were associated with a rise in cases and were similar to the seasonal patterns of other respiratory diseases.
Will this climatic factor help a country like India — where most cities have high temperature and humid weather conditions — contain the spread of coronavirus, especially considering that the summer has already begun?
Dr KK Aggarwal, president of Heart Care Foundation in India, told the Times of India that since viruses thrive in lower temperatures, COVID-19 has been rapidly spreading to “southeast Asian countries that are cooler and less humid than India”.
However, it must also be noted that the spread could also be engendered by the extensive travelling of infected persons, who, in turn, spread it to others, as seen in many of the recent cases reported in India.
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While the health experts TNM spoke to agreed that viruses, in general, cannot thrive in extreme temperatures, they could not say with certainty its significance in the current coronavirus outbreak.
“Viruses cannot survive in temperatures above 60 degree Celsius. However, as far as India is concerned, some places in north India record a maximum temperature of 26 degrees Celsius, while in south, it is now above 33 degree Celsius. Yet, this temperature is not sufficient to make the virus less potent,” said Dr Jayakrishnan AV, a neurosurgeon in Kerala and former president of Indian Medical Association (IMA), told TNM. Even Singapore, which recorded a temperature of around 23 to 33 degree Celsius in February, saw 110 coronavirus cases.
“Besides, the weather conditions will not be effective or applicable if the people are in closed spaces or large gatherings with air conditioners,” he added.
Dr Nancy Messionnier, director of the US-based Centers for Disease Control and Prevention, had said that it is “premature” to make such assumptions. Dr Navin Dang, a microbiologist in India, agrees.
“Unlike other coronaviruses, we are dealing with this strain of the same virus for the first time,” he said.
According to him, the current surveillance system, however good it is, has not been able to detect a case at airports. “A person may be in the incubation period (the time between contracting the virus and showing symptoms) when entering the country and the screening at airports may show negative. But after a few days, he may start showing symptoms and spread the infection,” he explained.
However, Dr Navin added that unlike 2009 flu pandemic or swine flu in parts of India, “we have more trained doctors, biomedical staff and state-of-the-art infrastructure to handle any situation, so there is no need to panic.”
As many health experts globally stress, irrespective of the seasonal patterns, it is too early to determine or even predict how this newly-identified coronavirus mutates or can be contagious in future. As insisted by health officials worldwide, wash hands thoroughly, use hand sanitisers, wear N95 masks, seek medical help if you develop symptoms, avoid organising or attending large gatherings and above all, do not believe or spread false messages.