As we continue to deal with COVID-19, clustered outbreaks should give us insight into what we can expect as the virus circulates through the population in the United States. When a group of people is subjected to widespread testing because they were in close proximity during an outbreak, what are the outcomes for that population?
One of the most newsworthy was the outbreak on the USS Roosevelt. As of April 24, 777 crew members had tested positive for the virus. It infected 15.5% of the sailors living in very close quarters. But according to reports 50% of these cases were completely asymptomatic. From Popular Mechanics:
Half of those that have tested positive, mostly young, healthy men and women under the age of 30, have proven asymptomatic—that is, they have no symptoms at all. This is a much larger number of asymptomatic carriers than researchers see in the U.S. general population, where roughly 25 percent of those who have tested positive are asymptomatic.
The delta between testing on the ship and testing in the general population is not surprising. The focus of testing on the ground has been on symptomatic individuals and those who may have been exposed to a positive patient.
This finding is buttressed by an even more interesting finding. From Reuters:
As mass coronavirus testing expands in prisons, large numbers of inmates are showing no symptoms. In four state prison systems — Arkansas, North Carolina, Ohio and Virginia — 96% of 3,277 inmates who tested positive for the coronavirus were asymptomatic, according to interviews with officials and records reviewed by Reuters. That’s out of 4,693 tests that included results on symptoms.
While there is no guarantee those tested will remain symptom-free, the symptoms can range anywhere from mild to severe. The key finding is the number of people who are testing positive for the virus with no reported symptoms. Especially given the results from one prison in Ohio:
They started with the Marion Correctional Institution, which houses 2,500 prisoners in north central Ohio, many of them older with pre-existing health conditions. After testing 2,300 inmates for the coronavirus, they were shocked. Of the 2,028 who tested positive, close to 95% had no symptoms.
Now there is an outbreak in Cass County, Indiana related to a Tyson meat processing plant. According to the Regenstrif Institute there have been 1187 tests after workplace and contact tracing. There have been 32 hospitalizations and with 14 of those being to the ICU and no deaths. To date 97% of cases related to this outbreak have not needed specialized care to deal with the virus.
There have also been outbreaks at a meat processing plant in South Dakota and other locations. The reason these outbreaks need to be evaluated is that they will give a much clearer picture of how many cases are asymptomatic or only produce mild symptoms. It will also give us a more precise assessment of the risk to older adults with preexisting conditions. The findings at Marion Correctional are surprising to say the least for the reported demographic.
This brings to mind questions that need to be answered sooner rather than later as we move to reopen the economy. First there needs to be an honest assessment about whether or not the CDC is underestimating asymptomatic spread based on these clusters. Second, are we dealing with a different mutation of the virus now in some areas of the country? It is quite possible for a virus to become less virulent as it mutates, which may account for a higher proportion of asymptomatic cases.
Finally, is it even possible to track the spread if a proportion between 50% and 96% of cases are asymptomatic rather than 25%? If not, it is imperative that our public health professionals begin to make clear the risks posed by the disease to various tranches of the population. Whether by age, preexisting condition or lifestyle choice, people need to be informed so they may approach reopening with an honest evaluation of their personal risk.
Because if these elevated numbers of asymptomatic cases hold, eventually we will all be Sweden.