Thursday, July 23, 2020

Coronavirus - how deadly?

A Wall Street Journal article tries to answer how deadly COVID-19 is. The article is behind a paywall. The following is my summary.

Dozens of research studies have been done to calculate an infection-fatality rate for Covid-19. Such research -- examining deaths out of the total number of infections, which includes unreported cases that can only be estimated -- suggests that Covid-19 kills from around 0.3% to 1.5% of people infected. Most studies put the rate between 0.5% and 1.0%, meaning that for every 1,000 people who get infected, from five to 10 would die on average. The average is about 0.68%. The U.S. CDC estimate is 0.65%.

The estimates suggest the new coronavirus is deadlier than the seasonal flu, which has an infection-fatality rate of about 0.1%. Among confirmed global cases for Covid-19, roughly 4.2% of those people died (3.6% in the USA thru July 22). The percent of deaths among people with confirmed infections is higher than the percent of deaths among all infections, since many milder and asymptomatic Covid-19 cases are not in the denominator for confirmed but are for all. The U.S. CDC has estimated that for every known case of Covid-19, roughly 10 more went unrecorded through the beginning of May. From March to early May, the total number of infections was likely 6 to 24 times greater than the number of reported cases depending on the state, the agency said in a paper published in the journal JAMA Internal Medicine.

Covid-19 is not as lethal as SARS, MERS, or Ebola. Their case fatality rates range from about 10% to over 50%. (The article doesn't give infection-fatality rates for them. Ebola was mainly in Africa, where I suspect data collection and reporting are very deficient.) The coronavirus is killing more people than the deadlier diseases because it has infected many more people.

The Covid-19 fatality rate varies a lot depending on age, sex and pre-existing medical conditions. Researchers in the U.S. and Switzerland examined data from the Swiss city of Geneva to calculate fatality rates for different age groups. They found those over 65 had an infection-fatality rate of 5.6% — 40 times the risk of someone in their 50s.

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