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Some level of social distancing may need to remain in place, at least intermittently, well into 2022, Harvard researchers suggest in an analysis published Tuesday.
Even with some type of restrictions implemented regularly over the next few years, new outbreaks of the coronavirus that causes COVID-19, called SARS-CoV-2, could be seen until 2025 or beyond, researchers suggest in the study, published in the journal Science.
"We found that one-time social distancing measures are likely to be insufficient to maintain the incidence of SARS-CoV-2 within the limits of critical care capacity in the United States," study co-author Dr. Stephen Kissler, a research fellow in the Department of Immunology and Infectious Diseases at Harvard T.H. Chan School of Public Health, said in a conference call with reporters on Tuesday.
"So, what seems could be necessary in the absence of other sorts of treatments, are intermittent social distancing periods to maintain the critical care the number of critical cases due to SARS-CoV-2 with the capacity able to be treated by hospital limitations within the United States," he added.
The paper adds to the growing amount of scientific evidence suggesting the virus, currently plaguing much of the globe, will not behave like its "closest cousin, SARS-CoV-1. That virus caused the SARS outbreak in the early 2000s, and was largerly eradicated after causing a brief pandemic. In fact, the new analysis suggests transmission could be more like that of pandemic influenza in that it will circulate seasonally.
That could change if an effective anti-COVID-19 vaccine is developed, allowing large parts of the global population to have immunity against the virus, the authors said.
As of Tuesday afternoon, roughly 2 million people have been infected with COVID-19 worldwide, according to figures from Johns Hopkins University. In the United States, nearly 600,000 have tested positive for the virus, and more than 25,000 have died.
For the new analysis, researchers developed models designed to project possible future waves of cases in order to map out how current approaches to containing the outbreak might impact disease spread. They used historical examples of the spread of infection associated with the family of beta coronaviruses, including the bug that causes the common cold.
The researchers found that, if U.S. states were to lift one-time social distancing measures by early June, the country could expect waves of cases through the fall, and tens of thousands of new cases overall through the first half of 2021. The modeling suggests the only way the country could see a dramatic reduction in new cases -- aside from development of a vaccine -- would be to maintain some level of social distancing through early next year.
Even then, a resurgence in new cases that could occur when or if the restrictions are lifted could be enough to overwhelm hospital capacity across the country. The researchers also say the United States could see a resurgence in cases once social distancing measures are lifted, even in July or August, contradicting suggestions as recently as mid-March that the virus may not survive the warm-weather months.
"The magnitude of such seasonality... is certainly not zero," said study co-author Marc Lipsitch, a director of the Center for Communicable Disease Dynamics at Harvard T.H. Chan School of Public Health. "It exists, but it is certainly not enough of a seasonal fluctuation for it to disappear in the summer in the absence of interventions."
"I don't want that part to get lost," Lipsitch added. "I think it's been a controversial topic with lots of people think lots of things. I think this is some of the most compelling quantitative evidence on the topic."