I have opened my presentation slides on pandemics (nearly 400 slides) to find this small subset. This is a graphic representation of how quickly the Spanish Flu spread across the US in 1918 in just a few weeks. Remember, we didn’t have air travel at the time, so long distance travel was by train and recall that the Model T Ford had only come on the market in 1908, so travel by automobile was still relatively new. This is a good illustration of how quickly things can move through the US, but when you think about how much easier and quicker transportation is today, it’s likely things will spread much more rapidly.
I will try to explain why my views of the impact of COVID-19 dramatically changed due to the cluster of cases in Italy. Of course, I’ll use a graph to try to make the concepts clearer.
One of the terms we use in epidemiology is called the incubation period. That is the time from which a person is first exposed to a communicable disease until they start showing symptoms of the disease. They also can start spreading the disease later during this time period. I’ve represented that with three horizontal bars with gradients somewhat indicating that they get more likely to spread infection as they get closer to the time they are identified as a patient. The incubation period for this disease is thought to be 14 days, which is the lengths of the bars I used.
The first two cases (purple) were a husband and wife who were tourists from China. It is thought that he caused her illness as well as well as 12 others. There is only one other case (orange) that shows up on 2/7. No more are identified until 2/21, when over the course of five days we have seen an additional 319 cases so far. That is one of the things that is so alarming to me. There are three possibilities that I can think of:
1. There were other cases that haven’t been identified that spread the disease. This could be good or bad, depending on how much of a proportion of the population are asymptomatic spreaders.
2. These three individuals combined are somehow responsible for the next 319 cases (so far), or worse, maybe just 1 or 2 of them are. If this is the case, that means at a minimum that one person was responsible for over 100 cases, and if it’s only 1 or 2 of them causing most of the spread, a number much higher.
3. In some individuals, the incubation period may be longer than 14 days.
People like this are called super spreaders. For comparison, during SARS it is thought that the majority of the disease in Singapore was spread by five of these types of individuals, the highest causing 76 cases.
This is a concept I covered earlier called the reproductive number, or R0 of a disease. It’s the average people infected by an individual that is infected. The WHO estimate had been 1.4-2.5, but a recent analysis (link below) of various literature indicates that the value is 1.4 to 6.49 and with an average of 3.28. For comparison, the Spanish Flu of 1918 was 1.2-3.0
Combining this with what I had described earlier of the differences between how I expected this to travel in the West versus the East is very alarming. We are looking at a disease that could easily rival 1918 in scope. The mortality numbers I have calculated assuming a 30% attack rate (the percentage of the world population that get infected), which is the estimated rate from 1918, are simply shocking. However, we do not know exactly how many people will be infected, so this could be far worse or far better.
I’m sorry this one was probably a little more technical and harder to grasp but some concepts but it’s late and I don’t have the energy to wordsmith. I will try to answer any questions though as I have time.
Disclaimer: This commentary is my own interpretation and does not represent the analysis by the government or my employer. The data is from the Johns Hopkins University’s Center for Systems Science and Engineering.
I had been hopeful that COVID-19 could be contained because of some of the differences between eastern and western philosophies and social practices.. My update on Feb 24 had a change in tone. Now that we have almost 5 days of outbreak data in Italy, I am very concerned about the ramifications of this globally.
This mirrors what was stated by Nancy Messonnier, the director of the CDC’s National Center for Immunization and Respiratory Diseases, “It’s not a question of if but rather a question of when and how many people will have severe illness.”
In short, start preparing. What transpires in Italy will be a good indicator of what will happen in other Western countries.
Please note that while the graphs of the diseases globally and in Italy use the same methodology, they have very different scales to represent the data. Don’t try to compare them to each other for that reason.
Disclaimer: This commentary is my own interpretation and does not represent the analysis by the government or my employer. The data is from the Johns Hopkins University’s Center for Systems Science and Engineering.
While the global picture continues to improve, I do have some concerns about COVID-19 at national levels. My biggest concern is the 215 cases in Italy.
One advantage of a strong central government in an outbreak situation is the ability to quickly enact policies to mitigate the spread of the virus. The rate at which hospitals were built in China was truly amazing as well.
Another reason I was a little less concerned about the disease in Asia is that respiratory hygiene measures such as mask use are now a part of the culture. This had started in Japan in 1918 during the Spanish Flu for obvious reasons, was reinforced by the Great Kanto Earthquake which led to a massive inferno in the city which resulted in smoke and ash that remained in the air for weeks. The influenza pandemic of 1934 further made mask use a common practice.
This was also spread by eastern medicine and philosophy, where “qi” is considered an essential element of health, which is tied to concepts of air, atmosphere, odor, etc. The use of masks quickly spread across eastern Asia for these reasons.
While eastern countries embrace the common good, in the west individualism and libertarian ideas make dealing with disease spread much more difficult. For example, think about how the antivax movement is causing a resurgence of measles in the US, which has been completely eliminated in 2000 as a result of vaccination efforts. Last year, there were 1282 cases in the US, which is a direct result of the antivax movement.
What people don’t seem to understand is that globally, measles has a case fatality rate of 15%, and about 0.2% in the US. In addition, about 25% of those infected with measles develop neurological damage. https://www.cdc.gov/vaccin…/pubs/pinkbook/downloads/meas.pdf
The other point I will add on this topic is that herd immunity is crucial in preventing disease spread. Among those vaccinated for measles, about 10% do not develop adequate antibody protection, and thus are susceptible. Herd immunity protects both that group of the population as well as those who have true medical contraindications to the vaccine.
Hence, the West is likely less prepared to deal with a large cluster of cases in some countries because of these philosophical differences and resistance to some basic public health interventions.
Disclaimer: This commentary is my own interpretation and does not represent the analysis by the government or my employer. The data is from the Johns Hopkins University’s Center for Systems Science and Engineering.
New cases are back at a level yesterday that is more what I expected. It’s hard to say why there was the three days of considerably lower cased.
It’s also troubling that the case fatality rate has been slowly climbing.
This is a good example of why it’s never a good idea to rely on a very short series of data in a long stretch to identify trends.
Disclaimer: This commentary is my own interpretation and does not represent the analysis by the government or my employer. The data is from the Johns Hopkins University’s Center for Systems Science and Engineering.
There appears to be a large jump in cases overnight. This is strictly due to the way that cases are being identified in Hubei province in China. Most testing has been through RNA tests, but results can take days. Hubei province decided to use CT scan to look for lung infections in order to start treatment earlier. This accounts for the large jump in cases. A similar thing occurred in the US in 1993 when the definition used for surveillance for AIDS changed, resulting in what looked like a massive jump that year.
A change in the testing methodology impacts two important variables: sensitivity and specificity. There are technical definitions for these but I’ll try to describe them in a way that makes them easier to understand.
In this case, switching to CT scan increased sensitivity. This essentially means that the test is more likely to capture cases. That’s why there is a large rise in the number of cases.
The other things that happens in this case is a decrease in specificity. A CT scan will identify any type of lung infection, not just from COVID-19. This is what is also known as a false positive test.
The takeaway is that this not something to get more concerned about. It makes sense to try to treat those at highest risk.
Disclaimer: This commentary is my own interpretation and does not represent the analysis by the government or my employer. The data is from the Johns Hopkins University’s Center for Systems Science and Engineering.
