There is so much information, misinformation and, at times, confusing information about COVID-19. For instance, the name of the disease is COVID-19, but it is caused by the newly circulating Coronavirus known as SARS-CoV-2. The virus has the first part of its name as “SARS” but is different from the virus that causes the disease SARS! Many people, including experts, use the names interchangeably, but they are not. It seems as if we can’t agree on something so simple, so how about things more complex? Well, enough about that; you get the point that it is understandable why people get confused.
The focus of this posting will be to share with you what I believe are highly reliable sites to get your information from, as well as to try to explain three things you are hearing a lot about that seem to be confusing, but are important:
1.the death rate (known as the crude case-fatality rate) of COVID-19
2.the expression” flattening the curve” (what it is and why it’s so important)
3.why there will not be a vaccine available in a matter of months
You likely have heard a wide array of figures being given as to what the death rate appears to be from COVID-19. When one hears different numbers being given, the tendency is to think that no one seems to know what they are talking about. The reality is that there is not any one mortality rate for the disease. The value being given by U.S. health authorities is ~1%, but, based on current information, seems more like 2%, and the number that the World Health Organization has given has been closer to 3.4% and China has published a rate of 2.3%. Why the discrepancy? Well, they are talking about different populations and some are blended numbers. Confused? Let me explain.
In epidemiology the mortality rate (often referred to as the crude case-fatality rate [CFR]) is actually a simple calculation: the number of fatal cases divided by the total number of cases (total number of fatal cases ÷ total number of cases). The result can be very misleading, however. If we look at the Chinese data and stratify it (arrange it by different groups) we see why there is such a great concern about this disease. In China, people older than age 80 had a CFR of 14.8%; those aged 70-79 years old had a CFR of 8%; those who had a critical case (~5% of the people infected) had a CFR of 49%! All of these numbers are true, but specific to the population group being looked at. Yet, when you hear experts speak, they don’t always clarify what group they are talking about.
There are currently 22.6 million American age 70-79 and 12.6 million aged 80 or older. We also know that people older than age 60 and especially with co-existing diseases are at a higher risk of having severe to critical disease when infected. That is one reason why we are concerned about a disease in which “80% have a mild case”. If you’re young and healthy that applies to you, but not the 33 million Americans who are in the higher risk group. If you haven’t thought about it already, you can see that calculation of an accurate case fatality rate is completely dependent on knowing how many cases there are within the population- be they diagnosed and undiagnosed. With the current lack of surveillance (identifying how many cases there are in the population versus how many are sick enough to meet the present criterion for testing), we really don’t know how many people are or have been infected. Without this knowledge, we can’t take the needed steps to limit the spread, because we don’t know how widespread it really is. A good analogy is that we are asking a color-blind person to tell us how many redheads there are in the room!
This leads into the next concept to explain- “flattening the curve”. In epidemiology we look at disease curves to guide our interventions and understandings of a disease. It is a simple graph; the number of cases over time (days, weeks, dates, etc.). It has been predicted that as the number of cases rise (especially if it is a sudden and dramatic one), the capacity of the healthcare system to deal with them (hospital admissions, ICU beds, respirators, etc.) could easily be overwhelmed; leading to a situation as is now seen in Italy, where difficult decisions as to whom to treat and not treat are being made. If we can take measures to slow down the spread such as social distancing (cancelling large gatherings, working from home, avoiding crowded areas, and, in some instances, closing schools) as well as common sense measures such as staying home when sick, hand washing and frequent cleaning of surfaces in public areas, we can decrease the number of cases over a given time and “flatten the curve out”.
So, any changes that delay the rapidity of the spread, and the number of cases in a given period of time, can help to prevent the healthcare system from being overwhelmed as susceptible and high-risk people become infected. This whole concept was graphically illustrated in a March 11 article by Helen Branswell in Statnews.com . The illustration shows that as we slow down the spread and hence, the number of cases in a given time period, the healthcare system would not be as overwhelmed as it could be.
Finally, let’s look at why there will not be a vaccine in a few months or even within the next six or nine months. This is because there is a very important sequence of events that must take place once a suitable vaccine candidate is found. It must first be demonstrated to be safe and effective in preventing the disease from developing; typically, in an animal model (animal testing in a mammal whose immune system is similar to ours). There are then 3 phases of studies: a small group of people who get the vaccine and are observed for side effects or major adverse reactions and followed over a period of time to identify late effects; a larger group to see if any of the concerns arise; then a larger group who may more closely mimic the population to be vaccinated (if the vaccine is still found to be safe). Finally, if all 3 human phases show no major issues, then adequate doses of the vaccine are produced. So, you can see that getting a safe vaccine out to the public is not an easy nor quick process.
Finally, in closing, I have listed some websites where you can get up-to-date and accurate, information about COVID-19:
MA Department of Public Health
Johns Hopkins Center for Health Security
CDC Coronavirus info page
CDC Travelers Coronavirus info page
NIH Coronavirus info page
American Academy of Family Physicians Coronavirus webpage
For those interested in real-time mapping and seeing where the cases are:
Johns Hopkins COVID-19 Real-time Mapping
University of Virgina COVID-19 real-time mapping