Welcome to Medicine with Dr Moran. I'm Dr. Keith Moran.
i've made this video because through the pandemic many of my patients have asked
me what is the covid fatality rate?
They wonder what their chances are if they catch the coronavirus.
They hear so many things in the media. Oh, here comes Lynx!
This is my cat Lynx and he's gone. They hear so many things in the media
and many of my patients are very fearful. Some patients unfortunately have
declined important medical testing because of concern of
acquiring the virus. It's always difficult in the beginning of a viral
outbreak to know the correct answer for what the
fatality rate is going to be. It obviously varies season to season
with influenza. Sometimes the strain of influenza is
more serious one year versus another and sometimes the vaccination may not be
terribly effective in any given year. Generally
for seasonal influenza the infection fatality rate is on the order of 0.1 to
0.2 percent.
The first thing to realize is the difference between the case fatality
rate and the infection fatality rate. The case fatality rate is the total
number of people who have died from the disease
divided by the total number of people who've tested positive.
Many patients who have minimal symptoms or no
symptoms do not get tested even though they are infected.
It's important to note that the infection fatality rate
is different from the case fatality rate. The infection fatality rate is the
number of people who died from the disease meaning the numerator is the
same but the denominator that you divide into
is the total number of people who get the infection.
Now it's more difficult to assess the total number of people who get infected
because you need to know how many people are out there that are
asymptomatic or minimally symptomatic. Typically we learn about these people
with antibody testing later. When people get any virus ultimately
antibodies get made specific to that virus which can be
measured once testing is available. In the case of a novel virus such as
the current coronavirus testing to check for antibodies always
takes a number of months in order to develop
the tests. In some instances though such as a
village or a small town in Italy a study done a
few months back they swabbed everybody with nasal swabs
to assess how many people had infection in the town
and in this particular study a lot of people had symptomatic disease there
but what they did not realize is that there were so many people with
asymptomatic disease. The same thing actually happened on the
cruise ship the Diamond Princess. Each person on the ship was tested with
a nasal swab for the virus. This way you have a really
good idea of how many people actually acquired the
infection on the ship not just the people who actually showed
up at health services on the ship. If you want to learn more
about the Diamond Princess cruise ship and asymptomatic infections
please click the link above.
Case fatality rates. These obviously vary country by country depending on a number
of factors. You can see what each country has if
you go to the John Hopkins website and take a look at their map and it will
show you how many people have died and how many people in that
country have been infected.
The reason why this variability is because of the medical care that could
occur country to country, the number of tests, as well as the age of the patients
that are affected. Obviously if an illness gets into
nursing homes and affects many elderly people there will be more deaths
and the overall case fatality rate will be much higher in that particular
country. Infection fatality rate. Again this means
that if you get the virus what's the likelihood of you dying from it?
And that's really what people want to know that's what my patients are asking
me. Unfortunately this is difficult to
assess and initially at the beginning of the pandemic
figures of two to three and a half percent were suggested.
Many different studies have been done in the last four months as well as
a recent meta-analysis to try to get a much more accurate figure.
In fact you may be aware that the beginning of May the CDC in Atlanta gave
different scenarios for the infection fatality rate.
They felt that the best scenario was an overall 0.4
infection mortality rate. They said that the chance of dying if
you got the virus was 1.3 percent if you're over 65,
0.2 percent if you were 50 to 64, and 0.05 percent if you're under fifty.
They estimated asymptomatic infections between twenty and fifty percent
with the best estimate of thirty five percent.
There have been a number of other studies including the Diamond Princess
cruise ship study which had a 0.8
mortality which when adjusted for age was probably much more close to 0.5
percent because there were a lot of elderly people on that cruise ship.
There have been studies from different parts of the world with varying
infection fatality rates ranging from 0.05 in iceland
to 1.5 percent in northern Italy where there are a lot of
elderly people. Locations with high burdens of nursing home deaths
may have much higher numbers. Locations where people are in close contact such
as large subway systems where high viral loads could be
transmitted person to person you would expect they will have much
higher infection fatality rates. This is something that people and even
physicians do not always think about. When we do a swab for the coronavirus
you either get a positive or a negative test result,
but it's really more than that. There have not been a lot of studies
actually quantifying the amount of virus found on the swabs.
Obviously if you get more virus in your nose
because more virus was transmitted the more likely you're going to have a more
severe illness.
Also there can be some methodological issues with the medical studies
including sample bias and accuracy of the antibody tests
to explain some of the variation.
As i mentioned there was a recent meta-analysis published in May
based on 13 studies looking at infection fatality rates.
The link is below in the description. The overall
infection fatality rate in the meta-analysis was 0.75
with confidence intervals at 0.4 to 1 percent.
A specific age stratified infection fatality rate would be helpful
and they were not able to provide that from the study.
That's really what people want. It would be much lower than the 0.75
percent i quoted in people who are under the age of 50 or even healthy
people under the age of 65.
This is the take home point as I've been telling my patients and friends for some
time now. The infection fatality rate of the virus
is much less than initially estimated. We still do not have an accurate
estimate and that may take some time but i think it's certainly safe at this
point to say that it's one percent or less.
If you're healthy and under the age of 50 the number is significantly less than
that. This is really the kind of number that
my patients want to know is what's the likelihood of me dying
from this. and as I say overall it's one percent or
less. Certainly if you're under 50 it's
much much less than that. Notwithstanding the coronavirus
illness is really something you don't want to get
yourself. You don't want to pass it along to somebody you love
and so it's still important to be vigilant. So you should do things
such as washing your hands, physically distance, and wear a mask
properly when you cannot physically distance.
These are words to live by not just to prevent this infection
but in general to prevent other infections such as the flu virus.
I hope you enjoyed learning about covid fatality rate with me today.
You've watched Medicine with Dr. Moran. I'm Dr Keith Moran.
Get healthy and stay healthy.