Like American President Donald Trump, President Rodrigo Duterte believes hot weather may reduce the transmission of the novel coronavirus behind the COVID-19 pandemic. The theory needs context.
The World Health Organization has said SARS-CoV-2 can be transmitted in areas with hot and humid climates.
Several studies have found the virus still rapidly spreading in countries with "summer" climates, the National Academies of Sciences, Engineering and Medicine said in an April report submitted to the White House.
But the report also said a number of experimental studies point to a possible relationship between higher temperatures and humidity levels and reduced survival of the virus “in the laboratory.”
It said, however, data that support a potential waning of cases in warmer and more humid seasons are limited, have limitations and must thus be interpreted with caution as many other factors influence transmission rates "in the real world” such as geography, people’s immunity to the virus and public health interventions.
In his prerecorded video message to the nation on May 4, Duterte reported the 9,485 confirmed COVID-19 cases in the Philippines as of that day and described the 1,315 recoveries as a “good number” compared to the 623 deaths.
Duterte then advanced his theory about the virus SARS-CoV-2:
Now, come to think of it really, mababa ang ano natin. They said that itong coronang putris na ‘to has a hard time surviving in a hot --- high temperature. So pagka ganun, maybe that explains the reason why na hindi naman masyado marami.
(Now come of think of it really, [the figures] are low. They said that this darn corona has a hard time surviving in a hot – high temperature. If that is so, maybe that explains the reason why there aren’t that many cases).
On March 17, when the Luzon-wide enhanced community quarantine took effect, the temperature in Metro Manila ranged from 26 to 30 degrees Celsius and humidity from 59 to 70 percent, according to weather data from the computational knowledge engine Wolfram Alpha.
On May 4, the day Duterte delivered his message, the metropolis recorded a temperature range of 28 to 37 degrees Celsius and humidity range of 53 to 79 percent.
The World Health Organization has said in its collection of mythbusters:
COVID-19 virus can be transmitted in areas with hot and humid climates.
You can catch COVID-19, no matter how sunny or hot the weather is. Countries with hot weather have reported cases of COVID-19.
Exposing yourself to the sun or to temperatures higher than 25C degrees DOES NOT prevent the coronavirus disease (COVID-19).
In the United States, Trump has suggested on at least three occasions that the new coronavirus would “go away” when temperatures warm.
Referring to Chinese president Xi Jinping and China’s response to the pandemic, Trump said in a Feb. 7 tweet: “…he will be successful, especially as the weather starts to warm & the virus hopefully becomes weaker, and then gone.”
In a meeting with governors on Feb. 10, he said, “(Y)ou know, a lot of people think that (the virus) goes away in April with the heat — as the heat comes in. Typically, that will go away in April.”
At a rally in New Hampshire that evening, the U.S. president said: "It looks like by April, you know in theory, when it gets a little warmer, it miraculously goes away — I hope that’s true.”
Responding to the White House’s request for information on the survival of SARS-CoV-2, the National Academies of Sciences, Engineering and Medicine said in their report that data on the transmission of the virus in different temperatures and humidity levels are mixed.
While some experimental studies indicate that the virus may transmit "less efficiently" in hotter and more humid places, the report said this may not significantly reduce the spread of COVID-19 because few people across the world are immune to the virus.
It also said reduced survival of SARS-CoV-2 at higher temperatures in experimental studies may be a function of the type of surface on which the virus is placed.
Changes in weather alone will not necessarily lead to declines in cases without extensive public health interventions, the report stressed.
The report also pointed out that "in the real world," the virus is still transmitting in countries with warm weather.
It said a study of the outbreak in China, the source of SARS-CoV-2, showed the virus spreading exponentially even at higher temperatures and humidity.
The report also cited the rapid virus spread in Australia and Iran during “summer” climates.
Frequent cleaning of hands with soap and water or alcohol-based hand rub and physical distancing are still the most effective protection against SARS-CoV-2, according to WHO and health experts.
The Philippines, which has imposed strict community quarantine in many areas since mid-March, has begun to “flatten the curve,” presidential spokesperson Harry Roque said in his May 5 virtual presser.
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