What we’ve learned in a year
The first documented case of COVID-19 infection in the United States occurred on Jan. 20, 2020 (there is strong evidence of undetected cases in prior months). That means the country has now had one year of experience with the virus that has caused the worst pandemic since the Spanish flu 100 years ago.
While we still don’t understand many things about COVID-19, in the past year we have acquired valuable knowledge about viral transmission, COVID testing, management of the critically ill, and keeping schools open. We also have vaccines – a pipedream a year ago. Here are some things we know today that we did not know when the first patient presented to a hospital in Washington state last January.
It was originally believed that people caught the virus by touching contaminated surfaces and through particle droplets transmitted through speaking, coughing and singing. Now we realize, that besides those two mechanisms inhalation of smaller particles – aerosols – are an opportunistic form of transmission, a potential problem in overcrowded spaces with poor ventilation. Masks confer a good level of protection but are not an absolute defense; handwashing and social distancing remain important adjuncts to masks. This is especially true with new virus strains that may be more contagious. Every pullback of mitigation effort when case numbers fell has been followed by epidemic resurgence.
The current status of COVID testing is far more sophisticated than a year ago, with different tests for different situations. The best test for diagnosing symptomatic patients is different from one identifying potential asymptomatic carriers who might transmit the virus. To diagnose a patient who has symptoms, a PCR assay on a nasal swab is the most practical and effective test.
To ascertain who may be actively contagious, e.g., for those concerned before family gatherings or travel, the rapid antigen test from saliva or nasal swab can detect high loads of virus in respiratory secretions. This test, although not as