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A second wave of COVID-19 could coincide with flu season this fall. Getty Images
  • If we do see a drop in infection rates over the summer, history suggests the pandemic may surge again later on in the year.
  • Early studies have found that people who contract the new coronavirus begin to develop antibodies against it within about 12 days.
  • However, questions remain about the strength and durability of that immune response.

As temperatures and humidity levels rise, there are hopes that infection rates of the new coronavirus may drop in the spring and summer — following a similar seasonal pattern as the flu and common cold.

However, experts are warning that the virus will continue to pose a public health threat throughout the spring and summer.

Even if we do see a drop in infection rates, history suggests the pandemic may surge again later on.

Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital in New York City, told Healthline that he expects a second wave of infections to hit in the fall.

If that second wave arrives as he expects, it will coincide with flu season. That means there may be a lot of people who become sick in the fall and winter, compounding the pressure on the healthcare system.

“It will likely be worse than the initial wave we experienced this spring,” Glatter predicted. “Combined with influenza, the intensity of both viruses combined could make our initial COVID-19 look benign.”

Scientists are just beginning to understand SARS-CoV-2, the new strain of coronavirus that’s responsible for COVID-19.

A lot of questions remain about the virus’s transmission dynamics, which make it difficult to predict how the virus will behave.

“Any projection is really more of a guess, going from pandemic experience in the past,” Dr. Eric Cioe-Pena, an emergency physician and director of global health at Northwell Health in New Hyde Park, New York, told Healthline.

“The big reason why I think a lot of people talk about two peaks — one being in the fall, one being in the spring — is that traditionally, that’s what happened with influenza,” he continued.

When the 1918 flu pandemic hit the United States, the first wave of infections occurred in March. A second and more lethal wave followed in October, when most of the deaths from the disease occurred.

Many respiratory viruses follow similar patterns, with infection rates peaking in the fall and winter. Those seasonal viruses include some but not all strains of coronavirus.

SARS-CoV-2 is related to other strains of coronavirus, including several viruses that cause the common cold and viruses that caused outbreaks of severe acute respiratory syndrome (SARS) in 2002 and Middle Eastern respiratory syndrome (MERS) in 2012.

The coronavirus strains that cause the common cold are transmitted more readily at colder temperatures and lower humidity levels than in warm, dry conditions. As a result, they cause more illness in the fall and winter than the spring or summer.

On the other hand, the coronavirus strains that caused outbreaks of SARS in 2002 and MERS in 2012 don’t appear to follow the same seasonal patterns.

This variability makes it hard to know how SARS-CoV-2 will behave.

“We’ve seen coronaviruses act in very different ways,” Cioe-Pena said.

“Some of them are very seasonal, some of them are not,” he continued, “so we don’t know what the pattern is going to be with this one.”

Although it’s possible that SARS-CoV-2 infections may ebb in the spring and summer, evidence from the Southern Hemisphere suggests the virus is readily transmissible in warm weather.

“There’s a lot of discussion right now about how the virus will do with heat and humidity — but we’ve seen some evidence in the Southern Hemisphere that it’s replicating just fine at the equator and below the equator,” Cioe-Pena said.

Experts north of the equator are watching southern countries closely to learn how seasonal shifts may affect the spread of the virus here.

The unfolding dynamics of the pandemic in southern countries may also shed light on how COVID-19 and influenza will interact in the fall.

“We can learn many valuable lessons from the behavior of influenza with COVID-19 from our colleagues in the Southern Hemisphere, as they experience both of these entities with their winter approaching,” Glatter said.

The body’s immune response to SARS-CoV-2 will also influence how the pandemic affects Americans in coming months.

Early studies have found that people who contract the new coronavirus begin to develop antibodies against it within about 12 days. However, questions remain about the strength and durability of that immune response.

“There’s two questions,” Cioe-Pena said. “Number one, are those antibodies effective in preventing another infection?”

“And the second question,” he continued, “is how long do those antibodies last?”

If the body’s immune response to the virus is strong and durable enough, a person may only be able to contract it once. As a result, infection rates may fall as more people become immune to the disease after contracting the virus.

If the body’s immune response isn’t strong or durable enough, a person who’s already had an infection will be able to get it again. This may contribute to high rates of infection in the fall and winter.

To prepare for a potential second wave of infections in the fall, Glatter emphasizes the importance of increasing healthcare capacity.

“We need to continue to prepare our hospitals for this reality, ramping up efforts to secure [personal protective equipment], and making sure we have adequate staffing and [intensive care unit] capability,” he said.

“A vaccine cannot arrive soon enough,” Glatter added.

In the meantime, Cioe-Pena encourages people to strike a safe balance between enjoying the warm weather while continuing to practice physical distancing.

He doesn’t think it’s a good idea to gather in large groups to play games of soccer, for example. But he does think we should take advantage of the nice weather to build up our mental health reserves for a tough fall.

“We have to maintain our social distancing to keep the virus at bay,” he said, “but I also think that we need to take a little bit of a mental health break, go outside, enjoy the weather, and enjoy being outdoors.”