I’ve received a lot of questions about the numbers coming out for the Coronavirus tests. A lot of people continue to ask “what does it mean?”
And that is a good question! Because there are 325 million people in this country (give or take) and ‘what does it mean?’ when 50,000 people are sick? Well, I can’t speak for the entire country, because that would take a very long time. But I can’t give some insight, regionally, into what the numbers may mean.
Before I get started, let’s get the latest numbers:
| Total Cases | Total Tested | Percent-positive | |
| Mississippi | 377 | 1943 | 19.40% |
| Louisiana | 1388 | 6751 | 20.56% |
| Alamaba | 242 | 2321 | 10.43% |
| Tennessee | 667 | 11144 | 5.99% |
| Arkansas | 236 | 1286 | 18.35% |
| Total | 2910 | 23445 | 12.41% |
This shows that, regionally, about 12-percent of the people who get tested actually have the virus. That is little lower than the numbers pulled from the cruise ships that were quarantined. You can almost think of those cruises as giant Petri dishes, in this case. Both the Diamond Princess and Grand Princess ships showed infection rates between 15- and 20-percent among the entire population (because everyone got a test, symptoms or not).
The interesting thing about those who tested positive is that, on the Diamond Princess, nearly half of those people were asymptomatic. That means they didn’t even know they had it yet!
There may have been many reasons for that. Perhaps the incubation period had not run its course yet, or some people may have a stronger immune response and fought it off without experiencing symptoms. We don’t know.
However, smart scientists and researchers have put together a paper, titled, “Estimating the asymptomatic proportion of coronavirus disease 2019 (COVID-19) cases on board the Diamond Princess cruise ship, Yokohama, Japan, 2020” to try and find out.
The wrote:
In this study, we conducted statistical modelling analyses on publicly available data to elucidate the asymptomatic proportion, along with the time of infection among the COVID-19 cases on board the Diamond Princess cruise ship. Our estimated asymptomatic proportion is at 17.9% (95%CrI: 15.5–20.2%), which overlaps with a recently derived estimate of 33.3% (95% confidence interval: 8.3–58.3%) from data of Japanese citizens evacuated from Wuhan [13]. Considering the reported similarity in viral loads between asymptomatic and symptomatic patients [14] and that transmission of SARS-CoV-2 by asymptomatic or paucisymptomatic cases may be possible, even though there is no clear evidence as yet of asymptomatic transmission, the relatively high proportion of asymptomatic infections could have public health implications. For instance, the United States Centers for Disease Control and Prevention recommends that contacts of asymptomatic cases self isolate for 14 days [15].
Making another extrapolation… if possible
Yeah, another one (You know, by the time this all over, you guys will all be experts on extrapolations and, hopefully, have a new-found appreciation for computer weather models). Okay, so if we assume a few things, the research may come in handy. But first let us do some mathematical reorganization and clarification. Remember solving for x?
Let’s go back to the Cruise ships.
3711 people were on the ship. 712 were infected. Of those 712, there were 381 who felt sick and had symptoms. there were 331 who did not feel sick (at the time of the testing) and were asymptomatic. That means that for every one person who had it and felt sick, one other person had it (well, the real ratio is around 1:0.86, but we will talk about that later), and didn’t feel sick. In the paper I reference above, they found that 17.9-percent (we’ll say 18-percent for easier math) of those infected would never actually come down with symptoms. Ever. The other 82.1-percent would eventually feel some kind of symptom.
That’s a lot of numbers, I know. But hang in there. Don’t get into Charlie’s level yet.
That means that of the entire infected population on the boat, all 712 people, about 18-percent (128 people) would be infected and never know it. But they tested everyone! So they were able to make that determination. And quarantine those people before they went about their lives and accidentally infected others.
That is not the case in the United States currently. So, we have to make some assumptions. If we assume that regionally, we are a “population” or a “community” then the “20-percent testing positive” for tests given seems reasonable given other research above. However, there is a problem. Because only certain people – those with a 100F fever, cough, and shortness of breath – are getting tested. What about all of the asymptomatic people?
Extrapolation and Math to the rescue!
Remember that for every one person getting tested that had symptomes, there was a person who had it with no symptoms. So from the regional numbers above, with 2,910 people testing positive, there are 2,502 people who have it with no symptoms. As of right now.
That means an estimated total of 5,412 total cases across the region within our “population” as of right now.
The bigger issue
Let’s circle back to our 18-percent of people with it that never have symptoms. If we assume the estimation of 5,412 people is correct. That means 18-percent of those 5,412 will never have symptoms and will be able to accidentally infect others.
What is 18-percent of 5412? About 974 people.
You may say, “974 people?! That’s it?!” And yeah, based on this estimation, that is it. But that isn’t the only story.
And with an R0 value of between 2 and 3 (we can pick 2.5 for easy math) how many people can they accidentally infect during the next two weeks? An additional 2,435 people. Of those 2,435 people, about 438 won’t know they’re infected. And those 438 will pass it to about 1,095 people. On top of the other 1,997 people who will give it to about 4,992 people.
That means the original 974 asymptomatic people, after just two more steps, are responsible for infecting 8,522 people. And of those 8,522 people now infected, 1,522 won’t know they have it, either.
Depending on the speed of incubation (which is different for each person) and how many people each next person comes into contact with, this can spread quickly or slower.
This is why it is important to practice social distancing.
Why these assumptions may not work
The good news is that the real world is not a cruise ship. People on cruise ships come into contact with each other – both directly and indirectly – far more often than in the walking around in the United States. So the transmission rate on a cruise ship is likely much higher than elsewhere. Because of that, more people were likely infected than normal.
And that may allow for errors to creep up in the data.
On top of that, this is a relatively small sample size. And the term “relative” is in reference to the population of the states above. 3711 people compared to 22.25 million can also allow for errors to creep into the data. Especially when extrapolating like I’ve done here.
That said… And this is really important! …Some people have symptoms and are not accounted for in this extrapolation because they are not getting tested. I know of three people who are – probably – fighting this thing off (based on symptoms) but can not afford to get a test.
So the numbers aren’t fully accurate, and may be much higher.
Another important note is that despite the ease of transmission on a cruise ship, and the extrapolation, the reaction to the virus – symptomatic vs. non-symptomatic – may not be affected. Just because more people had access to the virus, does not change their reaction to the virus once infected. And a cruise ship is a generally well-mixed population, albeit on average, skewed to an older generation.
For the whole country
Because I know people are going to ask… If we wanted to do this for the entire country, we could, but I don’t think the numbers would be as accurate. The bigger and bigger the extrapolation becomes, the more slop ends up in the data.
But if we take the numbers from the CDC, 54,453 and assume the same 86-percent have it but are asymptomatic, then an additional estimated 46,829 have the virus and are asymptomatic. That means, of the total estimated infected population – at this moment – of 101,282, about 18,321 will never know they got it. And may pass it along to others.
But again, slop in the data may be a problem. I don’t know how much I’d trust those numbers. That’s a big jump to make from 3711 people to 325 million.
Things you should be doing now
I know this can all seem overwhelming at times. The sheer amount of information being kicked out by every media outlets is like an avalanche.
So, here are some things: Stay home if you can! Gotta work? That’s understandable. Need food? Sure, head to the store. But try to skip any “for fun” activities in public where you would be interacting with others or in a place with multiple other people.
Some CDC’s guidance:
— Know where to get your local / state-level information
For Mississippi: https://msdh.ms.gov/msdhsite/_static/14,0,420.html
For Louisiana: http://ldh.la.gov/Coronavirus/
For Alabama: http://www.alabamapublichealth.gov/infectiousdiseases/2019-coronavirus.html
If you live in a state outside of the region, head to google and type in, “dept of health” followed by whatever state you live. Google should take you to that state’s department of health and on the main page, most states have a link to an update on the Coronavirus.
— Know the Symptoms
Look for things like a fever, dry cough, and shortness of breath. But also know when it may become an emergency. It becomes an emergency when you have difficulty breathing, a persistent pain or pressure in the chest, you develop general confusion, and if you develop bluish lips or face. Also recognize that body aches, weak stomach, nasal congestion, a sore throat, and other symptoms of the regular flu are not the same as the symptoms with Coronavirus.
— Stay home when you are sick
Any kind of sick. If you feel like you may have Coronavirus, call your health care provider’s office in advance of a visit. If you have any sickness, the CDC recommends to limit movement in the community, limit visitors, and practice good social distancing.
— Know if you are at a higher risk
Know what additional measures those at higher risk and who are vulnerable should take. Those at higher risk include older adults (over 60), people who have serious chronic medical conditions (like heart disease, diabetes, lung disease). Some research has indicated that people with asthma may also be included in the higher risk category.
— Take steps to mitigate your infection
The CDC recommends to “Implement steps to prevent illness” by washing high-traffic areas more often, washing hands with soap and water and if someone is sick, to isolate the sick person into a low-traffic area of the home.
— Create a Household Plan
Create a household plan of action in case of illness in the household or disruption of daily activities due to COVID-19 in the community.
