The following is a summary of questions I was asked by patients about COVID-19 this week. Please bear in mind that I am a neurologist. My main concern in writing and posting this articles is to protect public health. I hope this is helpful. If you are not finding what you need here, try the Maine CDC COVID-19 FAQ page, or the CDC in Atlanta FAQ page.
Isn’t COVID-19 like the flu?
No, but it is easy to see why people might make the comparison. COVID-19 and influenza are both respiratory illnesses that can be spread by droplets (coughs, sneezes, talking, dirty hands, dirty doorknobs, etc.). However, COVID-19 is about twice as infectious as the current seasonal flu in the U.S.
How do we know COVID-19 is more infectious than the flu?
One way to figure this out is the reproduction number, or R0 – pronounced “R-naught.” This basically tells us the number of people to whom an infected person will likely spread the disease. It is a way to describe how contagious a disease is. When R0 = 1 then and infected person will infect 1 other person. When the R0 = 10, then an infected person will infect 10 other people, and so on. Therefore, a lower number is better than a higher number. As we will see, it is possible to lower the number. When the R0 is less than 1, the epidemic is likely to stop, because an infected person is unlikely to spread disease to anyone.
The basic reproduction number of seasonal influenza is R0= 1.3. Thus, each infected person spreads the flu to about one other person (1.3 people, but let’s round down to keep it simple). That person spreads it to another person, and so on. The spread of seasonal influenza is usually person to person. So far, the data with COVID-19 is that the R0 = 2.2, close to twice as high: every person infected spreads it to two people, rounding down again, but it becomes person to people. That is a real problem, because it means that if nothing stands in the way, the number of cases doubles when it spreads. Based on data from the Wuhan, China outbreak, that occurred about every week during the early stage of the epidemic. (1) The spread might first go from 1 person, who spreads to 2 people, who spread to 2 each (4 more people), who spread to 8, and those 8 to another 16, to 32, to 64, to 128, to 256, to 512, to 1024, (keep doubling, and in ten more steps you have reached 1,048,576 new cases, and the aggregate is about 1.5 million). However, there are even more factors that influence an “exponential growth curve.”
Wuhan, China is a city of 11 million people. The city contains a large outdoor seafood market where the virus that causes COVID-19 is thought to have originated. There were several issues that fostered the growth of COVID-19. It was the season of the Chinese Lunar New Year (the largest annual mass travel event worldwide). There were huge crowds, people had come in from all over China, and all over the world. In the City of Wuhan community spread first occurred in mid-December. By mid-February, China reported over 77,000 cases. However, people who traveled to Wuhan returned home, and flights left through the end of 2019 until at least the first week of March, many of them to the U.S., and bringing the virus with them. Remember that many people may not have had any symptoms during travel. As of this am, Johns Hopkins reports there are 607,965 cases of COVID-19 affecting 177 countries. There are 104,837 cases in the U.S. This is far worse, and far more rapid than influenza. For a little more detail on R0, see footnote 1.
But doesn’t the flu kill more people?
This flu season from October 1, 2019 until March 14, 2020, the CDC in Atlanta estimated 38 – 54 million flu infections in the U.S., with 400,000 – 730,000 hospitalizations, and 23,000 – 62,000 deaths. (footnote 2) By comparison, in the U.S. there have so far been 1,711 deaths from COVID-19. (footnote 3) But, consider the fact that influenza had a six week lead on COVID-19. We don’t yet know how bad this will be. And, the case fatality rate (the number of people who will die from an illness as percentage of all those who are infected) is only about 0.1% for seasonal influenza. In Wuhan, China the case fatality rate was 2.5% (25 times higher than seasonal influenza in the U.S.), and in most parts of the U.S. the case fatality rate appears closer to 1% (10 times higher). In some outbreaks the case fatality has been as high as 5% (50 times higher). The bottom line is that COVID-19 is much more lethal than seasonal flu. This is why we are trying so hard to avoid it.
Even if COVID-19 is more deadly than the flu, please make no mistake, you should get a flu vaccine every year unless there is a clear medical reason not to get one. The numbers I have given for the flu should shock you. We lose an average of 30,000 Americans to the flu annually (some years much worse). You can do your part to stop the spread of the flu by getting your vaccine every year. As I mentioned in the last post, older people should also get a pneumonia vaccine. Stop the spread of infectious disease.
Will this be over before Easter?
I don’t think so. But there is reason to be hopeful that we will get this under control before summer. All viral illnesses seem to have a “wave” during which they pass through a community or population. Cases go up, peak, then come down. China claims to have leveled off the rate of new cases not long after mid-February, with a current 81,996 cases. I hope that is true. China also claims 75,099 recovered cases. Remember also that about 80% of cases are mild. In the U.S., which is several weeks behind China, we are still reporting growth in the number of cases and have seen nearly 900 recoveries (among those tested). If the wave of illness lasts about 8-9 weeks, we might see a decline in the rate of cases soon on the west coast. However, like everything else about this, it is complicated. It also requires social distancing to flatten the curve. As above, this disease is very contagious. Stay home, and avoid sick people.
Are there parts of the country, or maybe parts of our state that will be able to go back to business soon?
It is possible. A reasonable strategy might be to identify and isolate all cases in a community if the number is low (such as Montana). This would mean finding all contacts of sick people and isolating them, and not allowing new cases in. The problem is that we don’t have enough tests yet to do mass screening. So, the strategy is still social isolation. Stay home.
When will we have more tests?
A lot of work is being done. I understand that vendors are coming online as fast as possible. The most common test, the rt-PCR, requires a special reagent which is in short supply around the country. This test checks swabs from the nasopharynx for viral RNA. As far as I know, home test kits I have seen advertised are not yet FDA approved. There may soon be a blood test.
Do people develop resistance to COVID-19?
We think so. We are not yet sure, and there is not enough data to be sure. There is data that people who have recovered produce antibodies against the virus. Opinions around the globe are that it is likely that people will be immune to COVID-19 if they have recovered from a prior infection. The director of Allergy and Infectious Disease at the NIH, had this to say to Trevor Noah on March 27, 2020:
“I feel really confident that if this virus acts like every other virus that we know, once you get infected, get better, clear the virus, then you’ll have immunity that will protect you against reinfection.”
Anthony Facui, MD
Is there a vaccine?
Not yet, but people all over the world are working on it. We need a vaccine. For more about why we need a vaccine, see footnote 4.
Are there treatments for COVID-19?
There are currently no proven treatments. The strategy is largely supportive at this point. Fortunately, in the general population, 80% of cases are mild about 15% are moderate, and about 5% are severe, requiring mechanical ventilation. As discussed in prior posts, the numbers are not the same if we break it apart by age. Above age 60 the frequency of severe illness increases steeply.
What about hydroxychloroquine?
There has been some data to suggest it might be helpful, by making it less likely for the virus to bind to targeted cells in the lungs and GI tract. But there is no proof that this works, or that it is even safe to take during this illness. A drug for any condition should be tested and thoroughly vetted before use. Hydroxychloroquine is needed for rheumatologic diseases however, and it is unethical to take drugs out of supply that are needed by other people. Those who are selfishly attempting to take hydroxychloroquine prophylactically are doing so at a great cost to people with chronic disease.
What about ACE inhibitors and ARBs?
There is an association between angiotensin-converting enzyme 2 (ACE2) and SARS-CoV-2, the virus that causes COVID-19. (2) ACE2 is a co-receptor for viral entry for SARS-CoV-2 (is needed to help the virus get in the cell), and it might be related to pathogenesis (the evolution of disease) of COVID-19. ACE2 is seen in the human lung, GI tract, heart, and kidney. ACE inhibitors, which are normally prescribed to lower high blood pressure, might directly inhibit ACE2. The problem is that ACE2 is not inhibited by clinically prescribed ACEIs. (3) And, there is concern that the use of ACEIs and ARBs (angiotensin receptor blockers) might actually increase expression of ACE2, and that might increase susceptibility to the virus. We know from many animal and human studies that these drugs increase expression of ACE2 in the heart and brain, and there is limited evidence that the same might happen in the lungs. Still, as we try to find something that might help COVID-19, experts have called for both the use and the cessation of ACEIs, ARBs. The data is not there yet.
What about antivirals?
There is no data yet. Some of the antivirals used to treat HIV look interesting, but the same can be said about safety and appropriate use here.
What about plasma or serum from recovered people?
Data is being collected. This is a very promising area, and a very old idea. For about a century we have used the technique of collecting antibodies from recovered patients to treat the acutely ill. I have also read about trails harvesting specialized white blood cells from recovered people.
FOOTNOTE 1: R0 is not a fixed number. Factors within a population such as whether vaccines are used (and to what degree), the status of nutrition in a population, whether people in a community have some resistance to this virus, or whether some other infections are going around all come to bear on how infectious something is. That is why doctors, scientists, and epidemiologists discuss the effective R0. It is also why we ask you to take vaccines (see footnote 4 below).
FOOTNOTE 2: The reason for the lack of certainty is put by the CDC as follows: “Because influenza surveillance does not capture all cases of flu that occur in the U.S., CDC provides these estimated ranges to better reflect the larger burden of influenza. These estimates are calculated based on CDC’s weekly influenza surveillance data and are preliminary.”
FOOTNOTE 3: Sadly, the first death due to this infection in Maine occurred this week. Worldwide, there have been 28,125 deaths due to COVID-19 as of this am, 3/28/20.
FOOTNOTE 4: Measles is one of the most contagious infectious diseases and can cause explosive outbreaks. It has an R0 of between 12-18 in the U.S. The R0 can be higher in completely susceptible populations. Consider 1875, when measles arrived in the Fiji Islands. According to Hans Zinsser, in his excellent 1934 book Rats, Lice, and History, the King of the Fijis and his son returned home from a visit to Sydney, Australia, apparently bringing the infection back with them, and killing 40,000 people from a population of 150,000 (28% of the population). This population was naïve to measles. If a disease has been present for a while in a population, some immunity develops. Those people, who have survived an infection are either not susceptible or partially susceptible. It becomes much more complicated when most adults, but no small children are immune. And, there are many other factors such as hygiene, nutrition, and medical care that play a role. Such was the case with measles in the U.S. prior to the introduction of a safe and effective vaccine in 1968. Measles used to infect 3-4 million children in the U.S., resulting in up to 500 deaths annually. (4) There have been multiple measles outbreaks associated with unvaccinated children in the U.S. since then, though in 2019 we saw a 25 year high of over 1200 cases in 31 states. This was fueled by the anti-vaccine movement and those claiming religious exemption. Epidemiologists calculate that we need to vaccinate 95% of kindergarteners to reach a community protection threshold adequate to protect those who are not able to be vaccinated due to medical concerns. It is the ethical duty of all parents whose children can be vaccinated to do so in order to protect not just their own children, but those who are more vulnerable, and cannot have the vaccine.
REFERENCES
- Li, et al. Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus-Infected Pneumonia. NEJM 2020;382(13): 1199-1207.
- Zhou, et al. A pneumonia outbreak associated with a new coronavirus of probable bat origin. Nature. 2020;579(7798):270-273.
- Rice, et al. Evaluation of angiotensin-converting enzyme (ACE), its homologue ACE2 and neprilysin in angiotensin peptide metabolism. Biochem J. 2004;383(pt 1):45-51.
- Kohl, K, Gelline, B. Measles as Metaphor-What Resurgence Means for the Future of Immunization. JAMA 2020;323(10):914-915
