Does COVID-19 Weaken Over Time?

Earlier this week, the prominent and influential Italian physician Dr. Matteo Bassetti was criticized by the World Health Organization (WHO) for suggesting that COVID-19 was weakening. This was based upon his observation that his recently hospitalized patients with coronavirus were not as sick compared to just a month earlier. While the WHO argues that there is no scientific data to support this conclusion, the epidemiology appears to suggest otherwise. That is, when we review the COVID-19 experience in the U.S. a clear pattern emerges. As shown in the 2 graphs below (i.e., relative decline in the steepness of the curves; data from COVID Worldmeter), despite the high daily case rate over the past 4-6 weeks (~20,000-25,000 new cases in the U.S. per day), the rate of death is lower over this same time period (~2000 to ~1000 in the U.S. per day) with a continued downward trend.

So what factors may be accounting for the improvement in U.S. mortality rates in recent weeks?

Below are several possibilities:

1. Adherence to social distancing measures: Wearing masks, especially when indoors and in public places as well as maintaining social distance (~6 feet apart) will help to limit significant viral infectivity so should you encounter an asymptomatic person who is infected with the virus, the likelihood of being infected with a large viral load (resulting in pneumonia and/or disease requiring hospitalization) is reduced. While we do expect a surge in infection rates in upcoming weeks resulting from laxity of social distancing during the recent large gathering protests, it remains to be seen to what extent hospitalization rates will also rise. If the virus is inherently weakening (see #3 below), we may not see such an increase.

2. Better treatments in place: Compared to the initial phase of infectivity, therapies are emerging which may help hospitalized patients reduce viral complication rates, shorten duration of illness and potentially improve survival. Promising therapies to date include Remdesivir , convalescent plasma, and intravenous immunoglobulin therapy.

3. COVID-19 is weakening: While there is no scientific proof at this time that COVID-19 has weakened, clear evidence exists that life-threatening infection rates, have been largely reduced (or virtually eliminated) in China, Japan, Europe and the U.S. Unfortunately, in other areas of the world where COVID-19 transmission has only more recently become widespread, such as in Brazil and Mexico, virulent viral activity is quite robust.

While things are looking a little brighter in some parts of the world with respect to COVID-19, there is still no room for complacency until vaccination become available. Therefore, effective social practice measures must remain a top priority to maintain our safety and keep this virus at bay.

This post is dedicated to Dr. Glenn Barquet, an outstanding physician and colleague whose life was cut way too short due to COVID-19.

Michael Miller, MD is Professor of Medicine, Epidemiology & Public Health and a cardiologist at the University of Maryland School of Medicine in Baltimore, Maryland.  His recent book,  “Heal Your Heart: The Positive Emotions Prescription to Prevent & Reverse Heart Disease” is published by Penguin Random House, USA.