Top news, reports and insights for today:
- COVID-19 deaths surge on Tuesday to a new record high
After 2 consecutive days of falling deaths, Tuesday saw a return to double-digit increases as 2,378 new deaths were reported, a 10% rise. Fourteen states tied or exceeded their highest one-day death toll including New Jersey (362), Maryland (40), Massachussetts (113), Washington DC (15), Texas (31), North Carolina, Mississippi (13), Louisiana (129), Florida (72), Alabama (11), Ohio (56), Missouri (19), Idaho (6), and California (71).
What this means? This unwelcome news may be a signal that reporting of deaths was delayed over the holiday weekend. Another possibility is that states (New York among them) are starting to report “probable” COVID-19 deaths. It is also possible that daily ping-ponging of deaths will to continue in the short run. Hope that we were near peak was probably pre-mature.
- Coming clean on immunity to SARS-CoV-2
Yesterday, a well respected epidemiologist, Marc Lipsitch, wrote an opinion piece in the New York Times on the tricky question of immunity to the SARS-CoV-2 virus. People tend to think that once someone has been infected with a disease, they are immune to the disease forever. Like so many things in epidemiology, that is a cartoon of how things really work. Some diseases, like measles, do work that way. History buffs may be interested in how a Danish physician and early disease detective named Peter Panum figured this out in the 19th century by careful observation of an outbreak that occurred in the Faroe Islands in 1846. So far, what we don’t know about immunity to coronavirus is much greater than what we do know. Based on a few studies done of earlier coronavirus strains (SARS and MERS), it appears that immunity lasts for at least 2-3 years after initial infection. That’s tentative though because since both SARS and MERS are so lethal, we can’t do studies in which we intentionally expose patients to the virus, we can only observe those who get it naturally. Those studies have shown that over time, the effectiveness of antibodies declines, meaning that it seems unlikely that once infected, a person will have lifetime immunity. Dr. Lipsitch stresses we still don’t have enough hard evidence to know, but that we can make an “educated guess”. Based on his conceptual framework and statistical models, he suggests the following:
1) Most people will make antibodies that can neutralize the virus and protect against future infection, but the extent of protection will vary between people;
2) Antibodies will offer some protection over the medium term (“at least a year”)
3) the effectiveness of that immunity will decline over time.
The author cautions that there is still a lot we don’t know. For example, it’s still very unclear if some people can get re-infected with this virus after they recover. There is some data from South Korea and elsewhere showing that people who test negative after recovering later test positive again. We don’t yet know whether these are actual re-infections or that the negative test was a false result.
Why is this important? The lack of good data and careful studies is a source of frustration for everyone. When we get a particularly useful new study, we take notice and toss in on the pile of gradually accumulating evidence. We don’t fully trust any one study, but instead look at the big picture pattern, cross-referencing and comparing each individual piece of the puzzle. That’s what good disease detectives do. This study is an important one because it gives us pretty good reason to think that asymptomatic transmission is a big part of the COVID-19 story. PS: In the article, Dr. Lipsitch also suggests that because of inadequate testing, we may be under-estimating the number of people infected by as much as a factor of 10 in some places.
- New study demonstrates what we suspected: asymptomatic transmission is real
An important study was just published as a brief communication in Nature Medicine. The study was based on a careful look at 94 lab-confirmed COVID-19 infections in Guangzhou China. The study is important because they looked at viral load (the amount of virus present in a sample) from over 400 throat swabs in order to see when and for how long patients were contagious. Through painstaking contact tracing, they were able to give us a clearer picture of how this virus spreads. In the study, they documented 77 transmission events (defined as a new secondary infection resulting from contact with an index case). The main conclusions of this study were:
A) viral load peaked around the time that symptoms appeared or slightly earlier;
B) COVID-19 patients became infectious 2.3 days before the appearance of symptoms;
C) 44% of secondary infections occurred during the index cases’s pre-symptomatic period; and
D) peak infectiousness occurred about 1 day before symptoms started. The study does not tell us anything about whether patients who never have symptoms can pass the illness to others.
Why this matters? We have suspected that the SARS-CoV-2 virus must be spreading before symptoms are noticed, but before now we lacked confirmation. This kind of study is hard to do and very welcome because it gives us some of the most solid evidence yet that pre-symptomatic transmission is occurring: people can pass the disease before they know they are sick. This study reinforces the recent guidance that people should be wearing cloth face coverings in public.