Covid-19, the disease caused by the SARS-CoV-2 virus, will probably become a seasonal virus in countries with temperate climates, but only when herd immunity is achieved. Until then, according to a study published in Frontiers in Public Health, Covid-19 will continue to circulate throughout the seasons. These findings highlight the absolute importance of the public health measures needed at this time to control the virus.
“Covid-19 is here to stay and will continue to cause outbreaks throughout the year until herd immunity is achieved. Therefore, we have to learn to live with her and follow the best preventive measures, including the use of masks, physical distancing, hand hygiene, and avoiding meetings, “says the study’s lead author, Dr. Hassan. Zaraket, from the American University of Beirut (Lebanon).
According to another of the authors, Hadi yassine, from the University of Qatar (Doha), there could be multiple waves of COVID-19 before herd immunity is achieved.
Many respiratory viruses are known to follow seasonal patterns, especially in temperate regions. For example, flu and several types of coronaviruses that cause the common cold are known to peak in winter in temperate regions, but circulate year-round in tropical regions. The authors reviewed these seasonal viruses, examining the viral and host factors that control their seasonality, as well as the latest insights into the stability and transmission of SARS-CoV-2.
The researchers explain that the survival of the virus in the air and on surfaces, people’s susceptibility to infection, and human behaviors, such as overcrowding indoors, differ seasonally due to changes in temperature and humidity. These factors influence the transmission of respiratory viruses at different times of the year.
However, compared to other respiratory viruses such as influenza, COVID-19 has a higher transmission rate (R0), at least in part due to circulation in a population largely inexperienced in immunity.
This means that, unlike flu and other respiratory viruses, the factors that govern the seasonality of viruses cannot yet stop the spread of COVID-19 in the summer months. But, once herd immunity is achieved through natural infections and vaccines, the R0 should decrease substantially, making the virus more susceptible to seasonal factors.
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.
“This is still a new virus and despite the rapid growth of science about it, there are still things that are unknown. It remains to be seen in the future if our predictions are true or not. But we think it is very likely, given what we know so far that COVID-19 will eventually become seasonal, like other coronaviruses, “adds Zaraket.