A May 6th blog written on the science of COVID-19 transmission went viral almost over night. The blog, titled The Risks - Know Them - Avoid Them, was written by Erin S. Bromage, PhD, a comparative immunologist and professor of biology (specializing in immunology) at the University of Massachusetts Dartmouth. Using examples published in several countries, including China, since the start of the outbreak, Dr Bromage illustrates in plainspoken terms the risks and where they will wait for us as we move toward being together again, in close quarters.
Dr Bromage notes that his post was inspired by an article that appeared on the web site Quilette, titled COVID-19 Superspreader Events in 28 Countries: Critical Patterns and Lessons
1. Based on infectious dose studies with MERS and SARS, approximately how many viral particles are needed for a COVID-19 infection to take hold?
Answer: D. 1000 It is thought that as few as 1000 SARS-CoV-2 viral particles may be sufficient to create infection in a host. It is important to remember that this has yet to be determined experimentally.
A single cough releases about _____ droplets and droplets travel at approximately _____ miles per hour.
Answer: B. 3000 droplets and 50 mph Most droplets released by a cough are large and fall quickly, but many remain airborne and can be propelled across a room in only a few seconds.
A single sneeze releases about _____ droplets and droplets travel at approximately _____ miles per hour.
Answer: B. 30 000 and 200 mph Droplets released and propelled by a sneeze are small and travel rapidly across significant distance, eg, a room, public transportation, etc.
A cough or sneeze by a person infected with SARS-CoV2 may contain approximately how many virus particles?
Answer: B. 200 million virus particles If a person is infected, droplets released in just one cough or sneeze may contain as many as 200 million virus particles that will disperse in the air around them.
A Breath: When respiration is normal, a breath releases between 50 to 5000 droplets; most are low velocity and drop quickly to the ground. Even fewer droplets are released during nose breathing.And, of course, as there is no exhalation force with a breath, viral particles from the lower respiratory tract are not expelled.
Droplets released from breathing contain low levels of virus.Although a number has yet to be identified for SARS-CoV2, researchers use influenza as a guide. A person infected with influenza releases approximately 3 â 20 RNA copies per minute of breathing.
Presymptomatic or asymptomatic persons account for approximately what percentage of all COVID-19 infections and the majority of community-acquired transmissions?
Answer: C. 44% Just under one-half of all infections are transmitted by persons who carry the virus but never experience symptoms (asymptomatic) or who are infected but have yet to experience symptoms (presymptomatic).Viral shedding is possible for up to 5 days before symptoms begin.
Which of the above is NOT considered a superspreading event/environment?
Answer: B. Cruise ships Wide media coverage has painted cruise ship outbreaks as some of the worst. They actually don’t rank in the top 50 COVID-19 outbreaks accounted for to date. Of note, weddings, funerals, and birthdays accounted for 10% of early spreading events.
Choir practice: 60 singers observed early recommended precautions (no contact, 6 ft distancing) and practiced for 2.5 hrs in a church area the size of a volleyball court. One chorister was an asymptomatic carrier. Over the next 4 days, how many singers became sick?
Answer: D. 45 people became symptomaticSinging aerosolizes respiratory droplets very well and the deep breathing during singing draws droplets deep into the lungs. The 2.5-hr exposure during rehearsal with an adequate dose of virus was enough for infection to take hold. Over the 4 days, 45 choristers developed symptoms, 2 died. Average age was 67 yrs.
member Bob hugged at the funeral gets sick. Next: Bob goes to a birthday party attended by 9 people; they hug, share food, celebrate for 3 hrs; 7 become ill. Several days pass: Bob is very ill, hospitalized, and dies.
Bob’s legacy: 3 people infected at the birthday went to church, sang, passed the tithing dish and congregation members got sick. In all, Bob infected 16 people between the ages of 5 and 86 years; 3 of those 16 died.
TAKEAWAY: Successful Infection = Exposure x Time. Dr Bromage's blog, he says, was inspired by a piece written by Jonathan Kay in Quillete, titled COVID-19 Superspreader Events in 28 Countries: Critical Patterns and Lessons.
