Why COVID-19 is MUCH worse than the seasonal flu

This is the second in a series of posts about the COVID-19 pandemic. This installment is discussing why COVID-19 is much, much worse than the seasonal flu.

Here it is, in a nutshell: COVID-19 is more contagious, more deadly, already has more known long-term impacts, has no vaccine or truly effective treatments, and has no apparent seasonality.

Contagion

SARS-COV-2 is much more contagious. The median R0 (average number of people infected by each person when nobody is immune) is 5.7, or more optimistically 2.5. For the pandemic to go away, R0 would need to effectively be less than 1.  The estimate of the 1918 novel flu was between 1.2 and 2.4. (An R0 of 5.7 means we need over 80% of the population to be immune to reach effective herd immunity.)

Beyond that, the incubation period is long, and the number of transmissions before symptoms begin hovers near half those infected. And the duration of being contagious is longer, up to 10 days after the first symptoms. That means people are spreading it without knowing it, making contagion more likely. 

Mortality and long-term impact

Current best guess at mortality per infection is around 0.65%, though that number depends on several variables. If we have to reach herd immunity naturally in the US, 328.2 million x 0.82 = ~270 million Americans will have to be infected, resulting in ~1.75 million deaths. Because at some point people would hide in their homes and demand better contact tracing and quarantining, it is likely we wouldn't hit that.  But that is what the math says would be necessary if we just opened back up and tried to quickly reach herd immunity.

The estimate of the seasonal flu this past flu season is between 24,000 and 62,000 dead in the US. We are currently at ~156,000 from COVID-19, so already 2.5 to 6.5 times as many, and we are nowhere close to being done.

Perhaps even more ominous are the number of serious long-term impacts to those who survive COVID-19.  Permanent damage to the lungs, brain, and kidneys occurs frequently. It appears that sometimes it causes both Type-1 and Type-2 diabetes.  These will continue to be large problems for decades to come.

Treatments and Vaccines

There were no known treatments at the outset. The longer we deal with this, the more treatments are tried, and because some of these have some positive results, the mortality rate drops. But not as much as the flu, which we have been actively fighting for over a century. 

Similarly, there were no vaccines. Once we get vaccines, we hope they will be effective enough to reach at least temporary herd immunity.  But we aren't there yet.

Why? 

Historically, the main cause is ... it’s novel. The human immune system has never had to deal with it before, and so the response is slow and erratic. And because it is new, the health industry doesn't already have great treatments, much less vaccines or cures.

Is it worse for everyone?

No, many of the direct impacts are greater the older you are, especially with other conditions like COPD, diabetes, and heart conditions. Under some relatively high age (say 40 or 50 years old), the flu is worse for you, mortality-wise. But above that, it is worse, increasing dramatically the older you get.

But ... the comorbidities can strike even the lightly symptomatic or asymptomatic. And even if kids don't die, they can be a carrier to their parents, grandparents, teachers, daycare workers, party-goers, and others.  Children may become infected less frequently than adults, but that infection rate is still more than the flu.

And the secondary impacts are powerful. Mental health problems and emotional development issues caused by isolation are real issues for everyone, including children. Caregivers may avoid normal health activities, from getting good food to going to checkups to getting vaccines.  Fewer people going to hospitals means that the hospitals are laying people off precisely when they should be flexing their services up.