Coronavirus likely to continue spreading until 70% of US population is infected, warn experts

According to the researchers, states and health authorities should plan for the worst-case scenario, which involves a large second peak of cases in the fall of 2020


                            Coronavirus likely to continue spreading until 70% of US population is infected, warn experts
(Getty Images)
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The new coronavirus is likely to keep spreading for at least another 18 months to two years until 60% to 70% of the population has been infected, a team of pandemic experts from the US has predicted.

The researchers painted a picture of the COVID-19 pandemic and detail how it is behaving more like past influenza pandemics than any coronavirus has to date. And, because of that, certain inferences can be drawn — such as the fact that it may well last 18 to 24 months, especially given that only 5% to 15% of the US population is likely infected at this point, they explain.

The analysis is part of an initiative by the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota, US, titled, ‘COVID-19: The CIDRAP Viewpoint.’ 

“The virus caught the global community off guard, and its future course is still highly unpredictable; there is no crystal ball to tell us what the future holds and what the “end game” for controlling this pandemic will be,” says the report. It adds, “The epidemiology of other serious coronaviruses — SARS-CoV-1, the virus that causes severe acute respiratory syndrome or SARS and Middle East respiratory syndrome coronavirus (MERS-CoV) — is substantially different from that of SARS-CoV-2 (the virus that causes COVID-19). Therefore, these pathogens do not provide useful models for predicting what to expect with this pandemic. Alternatively, our best comparative model is pandemic influenza.”

The analysis has been done by Dr Kristine A. Moore, CIDRAP medical director; Dr Marc Lipsitch, director of the Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard TH Chan School of Public Health; John M. Barry, professor at Tulane University School of Public Health and Tropical Medicine and Dr Osterholm, director of CIDRAP.

The scientists say that key points emerge from observing the epidemiology of past influenza pandemics that may provide insight into the COVID-19 pandemic. Based on their analysis, the experts say that the length of the pandemic will likely be 18 to 24 months as herd immunity gradually develops in the human population.

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“This will take time since limited serosurveillance (provides estimates of antibody levels against vaccine-preventable diseases) data available to date suggest that a relatively small fraction of the population has been infected and infection rates likely vary substantially by geographic area. Given the transmissibility of SARS-CoV-2, 60% to 70% of the population may need to be immune to reach a critical threshold of herd immunity to halt the pandemic,” says the research team. According to the researchers, this may be complicated by the fact that experts do not yet know the duration of immunity to natural SARS-CoV-2 infection, which they say could be as short as a few months or as long as several years. “Based on seasonal coronaviruses, we can anticipate that even if immunity declines after exposure, there may still be some protection against disease severity and reduced contagiousness, but this remains to be assessed for SARS-CoV-2,” they say.

The course of the coronavirus pandemic also could be influenced by a vaccine, but a vaccine may not be available until at least some time in 2021. “And we don’t know what kinds of challenges could arise during vaccine development that could delay the timeline,” says the team.

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Given the transmissibility of SARS-CoV-2 (the virus that causes COVID-19), 60% to 70% of the population may need to be immune to reach a critical threshold of herd immunity to halt the coronavirus pandemic, say scientists. (Getty Images)

Three scenarios

The researchers also laid out three scenarios for how cases might ebb and flow in the coming months. In the first scenario, the team hypothesizes that the first wave of COVID-19 in spring 2020 is followed by a series of repetitive smaller waves that occur through the summer and then consistently over a 1- to 2-year period, gradually diminishing sometime in 2021. The occurrence of these waves may vary geographically and may depend on what mitigation measures are in place and how they are eased. “Depending on the height of the wave peaks, this scenario could require periodic reinstitution and subsequent relaxation of mitigation measures over the next 1 to 2 years,” says the report.

The experts say the second scenario may see the first wave of COVID-19 in spring 2020 being followed by a larger wave in the fall or winter of 2020 and one or more smaller subsequent waves in 2021. This pattern will require the reinstitution of mitigation measures in the fall in an attempt to drive down the spread of infection and prevent healthcare systems from being overwhelmed, they anticipate. 

A third scenario is where the first wave of COVID-19 in spring 2020 is followed by a “slow burn” of ongoing transmission and case occurrence but without a clear wave pattern. According to the experts, this pattern may vary somewhat geographically and may be influenced by the degree of mitigation measures in place in various areas. “While this third pattern was not seen with past influenza pandemics, it remains a possibility for COVID-19. This third scenario likely would not require the reinstitution of mitigation measures, although cases and deaths will continue to occur,” they recommend. 

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Recently, scientists from China said that the new coronavirus may not be eliminated and could instead return as a seasonal virus like the flu. The experts reason that the coronavirus will likely not disappear like SARS did because SARS-CoV-2 can infect people who do not show any symptoms of the disease. A White House testing blueprint also said that COVID-19 could co-circulate with influenza and other respiratory viruses in the fall. 

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Preparing for the worst-case scenario

According to the research team, states, territories, and tribal health authorities should plan for the worst-case scenario -- which involves a large second peak of cases in the fall of 2020, including no vaccine availability or herd immunity. 

Experts say states, territories, and tribal health authorities should plan for the worst-case scenario, which involves a large second peak of cases in the fall of 2020. (Getty Images)

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“Whichever scenario the pandemic follows (assuming at least some level of ongoing mitigation measures), we must be prepared for at least another 18 to 24 months of significant COVID-19 activity, with hotspots popping up periodically in diverse geographic areas,” say experts. 

They add, “As the pandemic wanes, it is likely that SARS-CoV-2 will continue to circulate in the human population and will synchronize to a seasonal pattern with diminished severity over time, as with other less pathogenic coronaviruses, such as the beta coronaviruses OC43 and HKU1, and past pandemic influenza viruses have done.” 

The experts suggest that government agencies and healthcare delivery organizations should develop strategies to ensure adequate protection for healthcare workers when disease incidence surges. Government officials should develop concrete plans, including triggers for reinstituting mitigation measures, for dealing with disease peaks when they occur, they add. “Risk communication messaging from government officials should incorporate the concept that this pandemic will not be over soon and that people need to be prepared for possible periodic resurgences of disease over the next years,” the team emphasizes. 

As of May 1, at least 3,257,66 cases of coronavirus have been reported globally, and more than 233,410 have died in the COVID-19 pandemic, according to the Johns Hopkins tracker. 

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