By Craig W. Hedberg, PhD
The COVID-19 pandemic has come to dominate our lives. Seemingly overnight, the global response has disrupted travel, trade, work, and social life. Although Professor Michael Osterholm and others had warned of just such an event for many years, the political will to develop and maintain the public health infrastructure needed to rapidly identify and respond to such an emergence never fully developed. Fledgling efforts to develop capacity and test response systems were not maintained. 

Heroic efforts are now being made across the globe to mitigate the individual and population effects of this novel corona virus.

The responses of scientific communities to this pandemic have been amazing. The virus was rapidly isolated and sequenced. The virus sequence, compared to corona virus sequences from known sources, identified a likely origin among wild animal populations that conformed to reported early transmission events within a live animal market. The high degree of concordance with the [2003] SARS corona virus helped guide initial control recommendations and identify potential drug treatments. Available sequences were rapidly used to develop diagnostic tests that were quickly employed by public health officials to track the spread of the emerging pandemic. 

Clinical trials of treatments and vaccines have been planned and implemented. Public health surveillance of cases was used to model the spread of the virus. Models of epidemic spread in China and elsewhere have formed the basis for the stringent control measures that have been implemented almost everywhere. 

The virus behind COVID-19 is related to other corona viruses that appear to circulate among bats and occasionally spread to terrestrial animals. It uses the same ACE2 [enzyme attached to the outer surface of cells] to enter cells that is used by the SARS corona virus. The rich supply of these ACE2 “receptors” in respiratory tract and lung tissues accounts for much of the clinical impact of COVID-19, as well as its transmission. It is spread by way of respiratory droplets, which settle out of the air within a few feet, and likely by droplet nuclei which may disseminate much further. 

Because this is a novel corona virus, the entire population is susceptible to infection. Most infections appear to involve mild to moderate illness with fever and respiratory symptoms, with 25 to 50 percent of infections being asymptomatic. A high proportion of severe illnesses and deaths have involved elderly persons and persons with underlying health issues such as a history of smoking, cardiovascular disease, diabetes, and obesity. Males appear to be at greater risk than females. 

Continued vigilance will be essential

Epidemiologic studies of cases, transmission models, and the characteristics of the virus have all contributed to the formation of public health control measures. Social distancing was invoked to keep people at least six feet away from each other, to avoid droplet transmission. However, because of spread from asymptomatic infections and spread of droplet nuclei over distances more than six feet, reducing spread in the community required the closure of all public settings that bring people together. 

Early results from modeling of surveillance data suggest it is working. The spread of COVID-19 is slowing in areas where social distancing is being strictly enforced. Continued vigilance to public health recommendations and adherence to good hygiene and handwashing practices are essential. We must be patient to avoid becoming patients. 

When it is clear that community-wide transmission has been suppressed to low levels, and the availability of test results permit rapid, sensitive, case detection and contact tracing, resumption of more normal work and social lives will be possible without undue risk for continued, uncontrolled spread of COVID-19. Short of that, we await the arrival of a safe and effective COVID-19 vaccine in the next couple of years.

For additional information and to follow new developments, check out cidrap.umn.edu, the U of M’s Center for Infectious Disease Research and Policy website.