Preventing COVID-19 infection

Although the dose of virus required for an infection undoubtedly varies between individuals, we have good information about how to avoid infection with the SARS-CoV-2 virus.

• Get vaccinated. All approved vaccines prevent a severe COVID-19 illness that would require hospitalization or cause death.
• Wear a mask.  The N95 and KN95 varieties filter out 95% of the virus, but a simple cloth mask will filter out 65% to 85%. In one study, only 19% of those who got infected while wearing a mask had any symptoms.
• Physical distancing.  The CDC says that 3 feet is enough for children; six feet or more is good for adults.
• Ventilation.  Avoid closed spaces. Being out of doors is much safer.
• Time.  The duration of exposure is important but not emphasized in most guidance.

A briefing from the University of California San Francisco (UCSF) pointed out the importance of limiting exposure to the COVID-19 virus both to prevent infection and to increase the odds that any infection will be asymptomatic or mild as an estimated 40% to 45% of infections are.  It is becoming clear that a small dose of virus particles gives the immune system the best chance of getting ahead of viral replication and clearing the virus before it causes symptoms, illness, and even death.  If you are infected with millions of virus particles, then the virus gets a head start.

An example of where everything went wrong was at a 2 ½-hour choir rehearsal in Washington State.  No masks, efficient spread of the virus by singing, a closed space, close proximity, and extended time all added up to a very high infection rate.  No one present was known to be ill, but after the rehearsal, 45 of 60 members in attendance were diagnosed with COVID-19 or had compatible symptoms, including three hospitalizations and two deaths. 

Think VMDVT for vaccination, mask, distance, ventilation, and time.

Back to top