June 25 covid-19 update

Both the South Africa and the United States reported their highest number of cases to date today (June 25): 6,579 in South Africa and 40,184 in the U.S. Italy, meanwhile, had only 296 new cases, down from over 6,000 new cases a day at the height of the Italian epidemic.

Here's the global view (visualization from worldometers.info). The world is on track to hit 10 million cases tomorrow (June 26), and half a million deaths in the next day or two.

We've discussed in these posts that there is a lag of several weeks between an increase in infections and an increase in deaths. We're in that lag right now in the U.S. Cases are increasing rapidly, but deaths remain under 1,000 a day. But it's not hard to do the math for how many of the 4,000 people newly diagnosed today are likely to die of covid-19. The U.S.'s case fatality rate (CFR) to date is 6%. It's possible that covid-19 patients will be treated more successfully over time, or that the people getting tested and diagnosed are increasingly younger and healthier people, which would decrease the CFR. Yet at a CFR of 6%, we will be seeing more than 2,000 deaths per day within a few weeks.

There was some important news today about the ratio of infected individuals to diagnosed cases in the U.S. You may recall that there are two factors that will determine the final death toll from this pandemic - the number of people who get infected, and the percentage of infected people who die (the infection fatality rate [IFR], which is different than the CFR). We've known since the beginning of the pandemic that in the absence of a vaccine, approximately 70% of a population would have to be infected to reach herd immunity. The big unknown has been what the IFR was, or put another way, the ratio of infections to diagnosed cases. Robert Redfield, the CDC Director, said today that this ratio is likely about 10:1, based on antibody test data from across the U.S. This means that there are 10 times as many SARS-Cov-2 infections in the U.S. as there are diagnosed cases.

This is in the range of what many epidemiologists have been saying all along. In fact, I told someone earlier today (before seeing the comments from Redfield) that my working assumption was that the ratio between infections and cases was about 10:1. My assumption on that was based on reading research and comments from people with far more expertise than I possess, so I'm not claiming any particular genius here, but I was still struck by how close the latest estimate (based on real-world data) was to what many experts have been assuming was the case. There are 2.4 million confirmed cases to date in the U.S., which means that there have been approximately 24 million infections, and that ~7% of Americans have been infected with SARS-CoV-2. So we are about 1/10 of the way to herd immunity, and can expect to see the death toll increase by about 10 times, barring any game changers such as significant advances in treating the disease. The U.S. has had over 124,000 deaths, so these latest data once again tell us that we are likely looking at over 1 million deaths to covid-19 in the U.S., unless we can slow transmission down enough to avoid reaching herd immunity before we have a vaccine. This is actually the best-case scenario, assuming that people have long-lasting immunity and can't be re-infected (which we don't yet know). If people can be re-infected, death rates could be higher. Also, if the ratio of infections to cases is about 10:1, a CFR of 6% is going to translate into an IFR of 0.6%.

In South Africa, the CFR to date is ~4% (about 2/3 of that in the U.S.). We don't know what the ratio of infections to cases is in S.A., and I don't want to speculate or assume it's similar to that in the U.S., as the two countries are seeing different rates of both new cases and testing. To date, the U.S. has tested about 3 times as much per capita as S.A. (1.57 compared to 0.51 tests per thousand people; you can see lots of data on this at ourworldindata.org/coronavirus-testing). I can say that unless S.A. is targeting its testing in incredibly sophisticated ways (to find those who are most likely to be infected), the data suggest that testing in S.A. is not staying ahead of the epidemic. This is based on the fact that the proportion of tests that are positive is increasing. (If the rate of testing was increasing faster than the spread of the virus, we would see this proportion fall.) For that matter, recent data from the U.S. show that testing is not staying ahead of the epidemic here either - see the line curving upwards? (Visualizations from ourworldindata.org/coronavirus-testing.)

And my visualizations for the week:

One final thought (although not a new one): WEAR YOUR MASK. I continue to be dumbfounded by all the Americans loudly protesting that laws about mask wearing are violating their Constitutional rights, as if there is an Amendment addressing their right to not wear a piece of cloth over their face when in a public place. No one is asking us to go fight a war, donate an organ, or even be jabbed in the arm with a life-saving vaccine. (I've also been horrified by all the Americans protesting they will not be vaccinated even if an effective vaccine for this virus is developed.) This particular piece of public health advice should be easy to follow. I had to go inside a giant American big box store today, something I haven't done since the pandemic started. I was appalled to see that although there was a sign on the entrance stating that everyone needed to have a mask to enter, more than half of the people in the store were not wearing masks, and the store didn't seem to be doing a thing about it. I'm sure this is happening all across the country... and our cases soar.

To address what seem to be common questions or misconceptions: 1) Masks do not have to stop viruses to be effective. They have to stop droplets, specifically droplets containing the virus that are breathed out by infected people. 2) Masks are more effective at preventing people from spreading the virus than breathing in the virus from infected people. So wear one for the sake of your fellow human beings, and realize that you may not know if you are infected. 3) Cloth masks will not eliminate the risk of transmission, but they will reduce it, and the point here is to reduce transmission in the population (i.e. a population-level benefit, more than an individual-level benefit).

My brother, a public school teacher, shared a meme today to the effect of, "If you want to homeschool your kids for the foreseeable future, by all means don't wear a mask." (I don't know anyone more desperate see this pandemic resolved than teachers who are having to simultaneously teach online and supervise remote learning for their own children!) And because a picture is worth a thousand worlds, please take a look at this picture showing what comes out of your mouth when you do and don't wear a mask, once it's allowed to grow in a petri dish. Yes, the gross stuff is bacteria - but the point is that a mask will stop droplets which can carry bacteria and viruses. We have few enough weapons in this fight, and we need to use every weapon we have. WEAR YOUR MASK.