newsinfomain coronavirus commentary

Dr Jyoti Somani and Professor Paul Tambyah, Infectious Diseases specialists from NUS Medicine, say that novel coronavirus cases may fall sharply by May when temperatures in the Northern Hemisphere - particularly China - warm up. They explain why in a commentary for CNA today.

The COVID-19 (Coronavirus Disease 2019) has now spread across the globe, reaching nearly every continent. In fact, it has infected more people in China than the Severe Acute Respiratory Syndrome (SARS) outbreak in 2003.

While the community learns more about the virus daily, questions are being raised about its rapid spread. One possibility is that this development could be related to climatic conditions.

Climate and the seasonal flu

In countries with temperate climates such as China and the United States, the flu season usually starts in December with a peak in January or February, after which cases tend to taper off. Thus there is reason to believe that the seasonal pattern of the novel coronavirus pneumonia may be similar to that of influenza infection and SARS, and thus cases may sharply fall by May, when temperatures in China warm up.

SARS disappeared in the northern summer of 2003 and has not reappeared significantly since. This seasonality of influenza and other respiratory viruses in temperate countries is thought to be related to factors that affect infectiousness (person to person spread) such as the dryness of the air, ambient air temperature and possibly ultraviolet solar radiation. Human factors may also contribute to the spread of influenza during the colder winters since more time may be spent indoors, presumably in closer contact with other persons.

The 2019-nCoV appears to be similar to other respiratory viruses such as influenza or the common cold (rhinovirus), which are spread by large droplets of saliva or phlegm from one person to another (either directly by cough or sneeze) or by contact. That happens when a person touches a contaminated surface and then touches his or her nose, mouth or eyes, inadvertently transmitting the virus. In fact, studies have shown that these respiratory droplets spread farther when the air is cold and dry.

Studies done many years ago showed that the “regular” coronavirus (one of the causes of the common cold) can survive on surfaces 30 times longer in places with a temperature of 6 degrees Celsius compared to those where the temperature is 20 degrees Celsius and humidity levels are high. More recently, scientists from Hong Kong University (HKU) including Professor Malik Peiris and Professor Seto Wing Hong showed that low temperatures and low relative humidity allowed the SARS virus to survive much longer than they would in high temperatures and humidity.

The HKU team argued that this may be the reason warm and humid Southeast Asian countries did not have SARS outbreaks, unlike Hong Kong and Singapore where in their words, there is “intensive use of air-conditioning”. Thus, just as with influenza, the 2019-nCoV may slow down when the sun starts to shine more and the weather warms up in temperate and subtropical countries.

Read more about this on Channel NewsAsia.

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