SARS-CoV-2 may become a 'seasonal virus', but not yet
Last Updated 18 September, 2020. Cellspect Co., Ltd.
A new review article published in Frontiers in Public Health suggests that COVID-19, the illness caused by the SARS-CoV-2 virus, may eventually become a seasonal illness like the flu, but only when the population achieves herd immunity, meaning a sufficient number of people are immune to prevent constant spread. This finding implied that COVID-19 will continue to cause outbreaks year-round and highlights the importance of following public health measures to control the virus. [1, 2]
Many respiratory viruses follow seasonal patterns, especially in temperate regions. For example, influenza regularly peak in winter and dwindle during the summer months. The same is true for certain types of coronaviruses that cause the common cold. Scientists don't know for sure why these viruses follow a seasonal pattern, but a number of factors are thought to play a role. For example, studies suggest that many respiratory viruses are more stable and linger in the air longer in environments with cold temperatures and low humidity. Human behaviors, such as gathering indoors in wintertime, could also boost transmission. 
These factors influence the transmission of respiratory viruses at different times of the year. Such seasonality has been reported for other coronaviruses, including those that emerged more recently such as NL63 and HKU1, which follow the same circulation pattern as influenza. However, in comparison to other respiratory viruses such as the flu, COVID-19 has a higher rate of transmission (R0). COVID-19's high R0 may be due, in part, to the absence of pre-existing immunity to the disease in most of the population. Thus, with a higher R0, the authors predict it will be harder for seasonal factors to push R0 below 1. This means that unlike the flu and other respiratory viruses, the factors governing seasonality of viruses cannot yet halt the spread of COVID-19 in the summer months. But, once herd immunity is attained through natural infections and vaccinations, the R0 should drop substantially, making the virus more susceptible to seasonal factors. 
“If a COVID-19 vaccine becomes available, it may reduce the spread, but it will likely not totally eliminate the virus”, the authors said. “That's because the vaccine will likely not be 100% effective, so some infections will still occur. In addition, the protection offered by the vaccine may wane with time, or the virus may mutate and evade immune protection.” Therefore, the author once again affirms the need for rigorous control measures to limit virus spread, until herd immunity is achieved. [1, 2]
From 1918 to 1940, it took more than 20 years for people to understand the influenza virus and make vaccines against it. For SARS-CoV-2, researchers have disclosed its genome, structure, transmission method, immune responses in a very short time, and had developed candidate vaccines as well as antiviral drugs. It is believed that this new virus can be controlled in a shorter time and better way. But still, people need to learn to live with this virus.
Amani Audi et al. Sep 15, 2020. “Seasonality of Respiratory Viral Infections: Will COVID-19 Follow Suit?” Front. Public Health
Rachael Rettner, Sep 15, 2020 “COVID-19 may become a seasonal virus” Live Science news.
Jacques Demongeot et al. May 3, 2020 “Temperature Decreases Spread Parameters of the New Covid-19 Case Dynamics” Biology (Basel). 9(5): 94.
Kristina Fiore et al. Sep 8, 2020 “When COVID-19 Really Is 'Just Another Flu'” Medical News and Free CME Online
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