A reader alerted me to the blog search function being screwed up, that is being fixed.
One of the first posts I wrote and a circumstance that caught my eye was the Diamond Princess cruise ship. The CDC published a paper on that recently. (CDC Paper) Without running through all the numbers again, the experience showed that asymptomatic cases were high, that even with regular close contact a very large number of people simply did not get infected and that serious illness was rare, even among a population that skewed old. People in cabins with four persons had the highest rate of infection, confirming the role of close contact, so let’s make everyone stay home, that would make a lot of sense. As the authors note, this study shows a very high asymptomatic rate, but everyone was tested, so it is likely an accurate reflection. This was an older population, so properly adjusted, it suggests a very low case and population fatality rate.
This study finds an astounding rate of antibody prevalence in Tokyo, largely reflecting asymptomatic cases. (Medrxiv Paper) Japan doesn’t do a lot of PCR testing, still sticking to a rational policy of only testing people who have symptoms. While the country has had some cases, there haven’t been many serious illnesses. This study was done among workers at one company, so not a random sample by any means. 11 locations across the city were used and 615 people volunteered to be tested. No person over age 70 was tested and symptomatic persons were excluded from participation. Seroprevalence rose from 6% to 47% over the time period of the study. These were almost all asymptomatic cases. Of 350 participants who took both tests, 21% who were negative on the first test became positive by the second, and 12% who were positive on the first test became negative. That latter finding is almost certainly a reflection of an inadequate assay to pick up the low levels of antibodies typically occurring after a mild infection and a switch from the antibodies common during acute infection to those more common in adaptive immunity. Let me make another observation: Japan has and had one of the highest rates of mask-wearing in the world! And Japan did not do a mandatory lockdown, people kept working and kept going out. And look at the huge spread of the disease. If this is at all reflective of general rates in the population of Tokyo, they must be at or close to slowing of transmission due to population immunity. Maybe we would all have been better off letting the pathogen basically run.
Here is another paper from the CDC, this one on contact tracing. (CDC Paper) Contact tracing is supposed to be the miracle cure for the epidemic, along with widespread testing and masks. The experience of two counties in North Carolina was recounted. In one county 48% of people and in another 35% failed to provide any contacts. Either they refused to do so or couldn’t remember. And of the contacts provided, 25% in one county and 48% in another could not be reached by phone. In one county, the median time from specimen collection to test result was 2 days, the median time from specimen collection to talking to the persons with positive results was 4 days and the median time between specimen collection and reaching contacts was 6 days. The other county had similar results. So much for the value of contact tracing.
And another CDC study, this one from my home state, looking at testing in nursing homes. (CDC Paper) Our state basically has had an epidemic only in the long-term care settings, it accounts for over 70% of all deaths. Two facilities were intensely studied and tested in this paper. 64% of residents and 33% of staff had positive test results. Infection control procedures were deemed lax at these facilities and getting test results took as long as 12 days. The high rate of cases among staff suggests they likely played a significant role in infection spread. Our state put out a “battle plan” to fight LTC cases, it obviously hasn’t work as in recent weeks we continue to see cases and a majority of deaths coming from that setting.
And here is a very helpful dashboard from the person who was tracking day care cases, a good site to look at periodically. She is now organizing to track school cases. Danger is that a lot of these cases are not infectious or even real cases. (School Dashboard)