COVID-19 will be a seasonal virus after herd immunity is reached

COVID-19 is set to become a seasonal illness in countries with temperate climates, but will remain a year-round threat until herd immunity is achieved, according to a new study published by Frontiers.

Respiratory viruses like the flu are not unusual during the colder months of the year, but COVID-19 will continue to circulate across the seasons for an indefinite time period. 

The findings highlight the urgent need for public health measures to control the virus. Study senior author Dr. Hassan Zaraket is an assistant professor of Virology at the American University of Beirut.

“COVID-19 is here to stay and it will continue to cause outbreaks year-round until herd immunity is achieved. Therefore, the public will need to learn to live with it and continue practicing the best prevention measures, including wearing masks, physical distancing, hand hygiene and avoidance of gatherings,” said Dr. Zaraket.

Study co-author Dr. Hadi Yassine explained that there could be multiple waves of COVID-19 before herd immunity is reached.

Several types of viruses, including those that cause common colds, are known to follow seasonal patterns. While these viruses peak in the winter months across temperate regions, they circulate year-round in tropical regions. 

The experts analyzed various seasonal viruses, investigating the factors that control their duration. They also reviewed the latest research on the stability and transmission of SARS-CoV-2.

As a result of changes in temperature and humidity, the duration of viruses and the susceptibility of human transmission differ across the seasons. For example, people are more likely to be crowded indoors during cold weather, increasing the potential spread of respiratory viruses.

However, in comparison to similar viruses such as the flu, COVID-19 has a higher rate of transmission. This is due, in part, to the fact that it is a new virus that people have not yet built up immunity against.

The factors that control the seasonality of common viruses cannot yet slow the spread of COVID-19 during the summer months. However, once a sufficient percentage of the population has become immune to SARS-COV-2 infection – whether through vaccination or previous infection – herd immunity will make COVID-19 susceptible to seasonal factors.

“The highest global COVID-19 infection rate per capita was recorded in the Gulf states, regardless of the hot summer season,” said Dr. Yassine. “Although this is majorly attributed to the rapid virus spread in closed communities, it affirms the need for rigorous control measures to limit virus spread, until herd immunity is achieved.”

There are other coronaviruses that have become seasonal over time, including NL63 and HKU1, which now follow the same circulation patterns as the flu.

“This remains a novel virus and despite the fast-growing body of science about it there are still things that are unknown,” said Dr. Zaraket. “Whether our predictions hold true or not remains to be seen in the future. But we think it’s highly likely, given what we know so far, COVID-19 will eventually become seasonal, like other coronaviruses.”

The study is published in the journal Frontiers in Public Health .

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By Chrissy Sexton, Earth.com Staff Writer