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COVID19 Suppression versus Mitigation

Asian countries attempted to reduce the infectivity of the COVID19 pandemic to R0 (R naught) by enforcing suppression. An R0 less than 1 indicates that each infected person transmits SARS-CoV-2 to less than one other person. Successful suppression requires early widespread testing of many people, even those without symptoms. People testing positive are isolated, so they cannot infect others.

The failure of the United States to implement early testing, caused it to rely on mitigation, rather than suppression, to slow the spread of disease.Mitigation efforts include handwashing, school and business closings, travel limitations and social distancing. The latter keeps people further apart, which decreases the likelihood of person to person transmission. The most vulnerable populations should be completely separated.

Mitigation focuses on protecting the most vulnerable from the effects of a disease that is already widespread throughout the community. By reducing the number of active cases at any given time, health care providers are better able to respond, without becoming overwhelmed. Reducing the intensity of the pandemic has been called “flattening the curve”.

Models published by the Imperial College COVID19 Response Team on March 26, 2020, estimate that a completely unmitigated COVID19 epidemic would peak in mid-June and result in 326 million infections and 2.9 million deaths in North America. Depending on how early widespread intensive social distancing is implemented, infections could be reduced to 17 to 90 million and deaths to 92,000 to 520,000. This mortality rate is nine-fold higher than a typical flu season. The United States’ decentralized authority, expensive health care, marginal public health network and low medical system capacity will make it more difficult to contain this pandemic.

In addition to a large number of deaths from COVID-19, the epidemic in the US will place a load well beyond the current capacity of hospitals to manage, especially for ICU care. The forecast predicts that 41 states will need more ICU beds than they currently have available and that 11 states may need to increase their ICU beds by 50% or more to meet patient needs before the current wave of the pandemic ends.

It is not known if SARS-COV-2 virus will continue spreading into the spring and summer, or if it will fade as other winter respiratory viruses do. If it ebbs, chances are it may return in the fall, perhaps even more voraciously.  If that happens, 40 to 70% of the world population could become infected, tens of millions could be hospitalized and millions could die.


IHME COVID-19 health service utilization forecasting team. Forecasting COVID-19 impact on hospital bed-days, ICU-days, ventilator days and deaths by US state in the next 4 months. MedRxiv. 26 March 2020. doi:

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