Covid-19 could eventually be seasonal, scientists say
The United States has been through waves, spikes and surges of Covid-19 throughout the pandemic, and now there is concern that the nation may be entering a new winter surge.
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Key takeaways:
"" Scientists have observed "waves" of coronavirus infections during the pandemic that ebb and flow across regions of the United States -- but the factors driving these patterns of infections are complex.
While no one can predict the future, "we're living through an intra-Covid world, and in a post-pandemic Covid world, I think what we would see is an endemic infection, not unlike the seasonal flu," Fayanju said.
Endemic means that a disease has a constant presence in a population -- but it's not overwhelming health systems or affecting an alarmingly large number of people as typically seen in a pandemic.
Some scientists point to human behaviors, such as travel, as fueling the waves.
Some think the waves are more evidence that Covid-19 is on its way to eventually becoming a seasonal endemic disease, with more cases occurring in the cold winter months at times when outdoor temperatures drop and people gather indoors.
Others argue that seasonal waves of Covid-19 could be more complex, since during the pandemic there have been both expected winter surges and less-expected summer surges, too.
"We need more research to disentangle all the factors that may link seasonality to Covid-19 cases," Dr. Hawre Jalal, assistant professor at the University of Pittsburgh, told CNN.
But there is one thing many scientists agree on -- coronavirus infections in the future could follow seasonal cycles.
'There will always be this underlying seasonal rhythm'
"Seasonality is real," said Dr. Donald Burke, professor and former dean of the University of Pittsburgh Graduate School of Public Health."We think that it will be seasonal for the foreseeable future," Burke said.
One study by researchers in Spain, published in October in the journal Nature Computational Science, classifies Covid-19 as a "seasonal low-temperature infection."
Separately, Burke and his colleague Jalal co-authored two preprint papers that describe the seasonal patterns of the pandemic's waves so far and suggest that these patterns may repeat in subsequent years. [...]
"Since it has been doing it twice so predictably, it's highly likely that a winter wave will happen again," Jalal told CNN.
"That doesn't mean that we should give up and say, 'It's seasonal, we just have to go with that.' I think a very important distinction to make is that we have some predictable pattern to it, so we can prepare for it," Jalal said. "You can make the public health services available before the wave starts."
Even though Covid-19 could become seasonal in the future, it is important to remember that the world is still grappling with a pandemic right now. We have not yet entered an endemic phase, said Sen Pei, assistant professor of environmental health sciences at Columbia University's Mailman School of Public Health.
So, while seasonality certainly could play a role in an upcoming winter surge this year, so could low vaccination rates and the spread of the highly transmissible Delta variant -- which dominates in the United States and around the world -- and the newly identified Omicron variant.
"People should take precautions during the winter," Pei told CNN.
He says this surge may be caused by several factors. "The first one will be the emergence of the new Omicron virus. I think that's the most important factor right now. And the second one will be seasonality of the virus and impacts of climate factors like temperature, humidity and also human behaviors -- people will gather more indoors during the wintertime."
Pei added that vaccination and booster shots "will also play an important role in reducing severe disease outcomes."
Yet once the coronavirus becomes endemic -- and case rates, hospitalizations and deaths fall to very low numbers -- the United States could see more pronounced seasonal patterns in infection rates than what are occurring now.
"I think still we are still far away from that," Pei told CNN.
"We will not enter into an endemic phase until the large majority of the population has immunity to the virus either from infection or from vaccination," he said. "The case fatality rate is still very high, much higher than flu, and a large proportion of the population still do not have immunity."
When will the coronavirus become endemic?
State and local health departments plan to meet with the CDC in the new year to discuss what type of data or metric will be needed to determine that the coronavirus pandemic has ended and shifted into an endemic phase, Lori Tremmel Freeman, chief executive officer of the National Association of City and County Health Officials, told CNN on Wednesday."We plan to begin having listening sessions in early January to talk with jurisdictions and their health officials about what we need to be thinking about to transition from pandemic to endemic. The idea is to envision what this looks like long-term and what metrics and considerations would be utilized to make the determination," Freeman said.
As Covid-19 transitions into an endemic disease, any seasonal patterns the virus might follow warrant discussion, Freeman added.
"We would all like to view that as a possibility -- where we're just tackling the season and trying to manage one season over the next in terms of severity and other aspects of disease transmission," Freeman said, calling it "crucial" to discuss long-term vaccination and mitigation plans.
"There are still many unknowns that it sometimes feels premature and overwhelming to predict what might happen to even make plans, but it is necessary." ""
