Will the COVID-19 outbreak burn out in the summer as happened with the SARS epidemic in 2003?
That is what many hope, including U.S. President Donald Trump. Some scientists are also speculating that the coronavirus will not survive long in warmer environments. But whether this is true is still up in the air.
The number of new confirmed cases has shown signs of slowing over the past several days, and more patients are being released from hospitals every day. But the point when the number of infected people declines is still not in sight.
Zhong Nanshan, a leading Chinese respiratory expert who became famous for his role in the 2003 SARS epidemic, said on Monday that he expects the number of new cases to peak in late February. But whether that would mark the turning point depends on what effect resumption of work across China would have on the spread of the disease.
Wang Chen, a respiratory expert at the Chinese Academy of Engineering, told state broadcaster CCTV that appropriate quarantine measures combined with warm weather will help curb the spread.
Theoretically, the COVID-19 virus -- part of the coronavirus family that also includes SARS and MERS -- is sensitive to temperature. All viruses are made up of a nucleic acid molecule inside a protein shell called a capsid. Some viruses, such as coronavirus, have an external membrane outside the shell. The membrane is relatively sensitive to heat.
COVID-19 remains stable at 4 degrees Celsius and can survive for several years at 60 degrees below zero, according to the Chinese Center for Disease Control and Prevention. In higher temperatures, its resistance declines, but the temperature affects only the virus' survival time, not its ability to infect, the center says.
Similar results were found with the SARS coronavirus. SARS remains stable at 4 degrees Celsius, but will lose its activeness in three days at 37 degrees and can survive for only 15 minutes at 70 degrees Celsius below zero, according to research by Bao Zuoyi and Liu Yongjian at China's Academy of Military Medical Sciences.
During the 2003 SARS outbreak, for every rise of 1 degree Celsius in Hong Kong, where the virus killed almost 300 people, the number of confirmed cases declined by 3.6. The SARS outbreak lasted about eight months.
Similar to COVID-19, the first SARS case was recorded late in the year. The number of confirmed cases peaked in April 2003, and no more patients were found in July. Scientists have never discovered a cure for SARS, and it is widely believed the virus dies off during warm weather.
According to the 2007 book "SARS: How a Global Epidemic Was Stopped" by Shigeru Omi, regional director of the World Health Organization, the United Nations health agency attributed the defeat of the epidemic to transparent reporting of cases, efforts to control the flow of infected people, and warm weather.
But differences between SARS and COVID-19 make it difficult to predict the resilience of the new virus. Unlike SARS, which can only infect others by patients with a fever, people with COVID-19 can spread the disease without exhibiting any symptoms, making it much harder to control the outbreak.
A recent study showed that COVID-19 is far more contagious than SARS. Published on Feb. 15 by the medical research archive bioRxiv, the study was conducted by a team led by University of Texas researcher Jason McLellan, who for years has been researching different types of coronaviruses such as SARS and MERS.
As temperatures rise, coronavirus floats in the air or attaches to surfaces -- both places where it can survive for only a short time. But once in the body, its ability to infect does not decrease, said Ma Ke, a doctor at Wuhan Tongji Hospital.
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