Hello, Welcome to Medicine with Dr. Moran. I'm Dr. Keith Moran. I've been asked a lot about how this particular coronavirus pandemic compares to other serious infectious outbreaks.
This video is about the different types of coronaviruses and the odds of dying from each one. Most people haven't heard about the coronaviruses before the last outbreak in 2003 but actually many of you have had coronavirus infections before. There are seven main coronaviruses which can affect humans. They are listed on this slide. The first four coronaviruses produce common colds in adults.
They're responsible for about 33% of upper respiratory tract infections during winter outbreaks and 5% to 10% of overall colds in adults. These viruses are seasonal and they're identified between December and May with the peak in January and February. Only two and a half percent of infections were identified between June and September.
Transmission for the common cold is through direct contact with large secretions which are large aerosol droplets. Reinfection is common because immunity tends to wane meaning that the antibodies that you make against the viruses they tend to wane with time.
There's no current treatment for common cold coronaviruses. These common cold coronaviruses do not typically lead to death by themselves other than the fact that they can set in motion secondary bacterial infections and other complications that might lead to death in older people. This now brings us to three other coronaviruses which cause significant disease in humans these I'm sure you've heard of. The first one is MERS, which is the Middle Eastern Respiratory Syndrome. MERS COV-2 was isolated in 2012.
It's been found primarily in the Arabian peninsula particularly Saudi Arabia. The last significant outbreak was in 2015 but cases are still being reported globally. Cases have occurred worldwide secondary to travel from the Arabian peninsula. It is believed that bats are the reservoir for this particular virus and that camels most likely serve as the hosts. So human to camel interactions can transmit the virus and then subsequent human to human transmission occurs.
The incubation period for this particular virus of course is the time where you get the infection to the first symptoms which typically is five days for the MERS virus. The range is two to fourteen days. The symptoms are fever, cough, shortness of breath, myalgias, and GI symptoms in about 20% of patients. Acute Respiratory Distress syndrome can happen secondary to Pneumonia. Real-time PCR testing of lower respiratory tract specimens as opposed to upper respiratory tract specimens for example from the throat or mouth is what's recommended here.
This is because this particular virus tends to infect the lower respiratory tract and there's minimal infection in the upper respiratory tract. Antibody tests have been made for MERS. There isn't a vaccine for MERS and there isn't any treatment for MERS either. The next coronavirus to talk about is SARS. SARS had a worldwide outbreak in 2003.
There were 8096 cases reported. The initial cases were noted in China subsequently there was spread to Hong Kong, Vietnam, Singapore, and Canada. PCR testing is diagnostic from the respiratory tract typically the lower respiratory tract. Because this virus the SARS virus much like MERS infects primarily the cells of the lower respiratory tract. The current Coronavirus causing Covid-19 tends to affect both upper and lower respiratory tracts and so is much more infectious than both SARS and MERS.
So there's been much more spread of the current coronavirus Covid-19 pandemic for SARS. antibody testing can be done. The reservoir for SARS is likely bats or possibly the Civet.
Spread was believed to be droplet but other forms of transmission were not completely excluded. This gives a similar illness with fever, malaise, headache, myalgias, and progressive respiratory failure.
Much like Covid-19 and much like MERS because really the clinical presentation of all three of these Coronaviruses are extremely similar. As far as treatment goes for SARS there's no antiviral therapy. Steroids are not recommended There's no vaccine. Antibody plasma has not been used. Surgical masks and N-95 respirators were studied during the SARS epidemic of 2003 and they were found to be useful in blocking the spread of SARS just like they're also helpful against influenza-like illnesses and other viral infections or even bacterial pneumonia for that matter.
The virus that's causing the current Covid-19 pandemic is the SARS Cov-2 virus. Remember that the virus is called SARS Cov-2 and the illness is actually called Covid-19. It's just like the fact that HIV is the virus that causes the illness AIDS. The Coronavirus is seen on the slide and like all of the Coronaviruses it looks like a crown thus its name coronavirus.
This particular virus of course was first discovered in Wuhan China.
Covid-19 stands for Coronavirus Infectious Disease 2019. It is believed to have come from an animal as it has close similarity to bat Coronaviruses but it also may have come from pangolins. This is yet to be determined. This makes it a zoonotic disease which means an animal disease just like SARS and MERS. As everyone knows this virus spreads between humans through close contact from respiratory droplets just like SARS and MERS.
This slide shows the odds of death from the coronaviruses MERS SARS and Covid19 which lead to serious human infection.
On the slide the death rate from MERS is 34%. Which was as of late September 2019 and it's based on an average of a number of studies. This is the case fatality rate and likely is a significant overestimate. Despite this it's quite high.
There's no data on the infection fatality rate. This is really what people want to know is that if i get infected how likely it is it that i'm going to die. Whereas case fatality rate only looks at the cases that come to people and not everybody that actually gets the virus and the reason why there's no infection fatality rate is there's not been widespread population testing in the Arabian peninsula.
To know what the chance of dying is if you get infected. There was a single study of 47 patients and in this single study case fatality rates rose with increasing age from 39% in the group younger than 50 years of age to 48% in those younger than 60 and 75% in people age 60 or older.
Small studies and lack of widespread antibody testing prevents us from knowing the true infectious fatality rate. Comorbidities were shown to lead to a higher risk of fatal infection as one might expect.
For SARS in 2003 there were 8,096 cases reported with 774 deaths. So the case fatality rate was 9.6% Finally, for Covid-19 case fatality rates across the globe have been reported in the 2% to 5% in general but widespread testing up for the virus with swabs or using antibody tests have demonstrated that the infection is much more widespread and that infection fatality rates are much lower they're in the 0.
3% to at most 1% range. For further details have a look at my videos on Odds of dying from coronavirus. There is a link below in the description. The chance of death of course varies by age and people below the age of 50 the likelihood of dying if you acquire the virus is less than one in a thousand.
It would be even less than this number if you're younger than 30.
In your 50's the chance of dying is 0.3%. In your 60's 1.3% in your 70's 4.6% and it's about 25% if you're over 80 years of age.
Now I always try to say something interesting towards the end of the video for those viewers who watch to the end. I talked at the beginning about the Coronaviruses that caused the common cold. I mentioned that many people have been exposed to these viruses. These common cold viruses have things in common with the current Coronavirus pandemic. A recent study which really has not been widely reported in the media indicates that about 30% of people in their study have some degree of immunity to the current coronavirus.
Even if you've not been exposed this may explain why so many people are asymptomatic. Essentially we have two types of immunity in the human body one is called Humeral Immunity with antibodies and this is the reason why Convalescent Plasma which has antibodies is being used as a potential treatment. The other kind of immunity is Cell Mediated Immunity and this is done through a type of white cell called a T-cell. In this particular study I'm talking about they found that 30% of people had T-cell immunity. This type of immunity means that the T-cells will recognize the virus and directly destroy it and it's likely that the T-cells have learned by destroying other coronaviruses that people have had in the past.
So that it will also recognize this new kind of Coronavirus, the Covid-19 virus. Now this likely has some bearing upon how many people need to be infected before herd immunity occurs. Some scientists believe that significant herd immunity may occur with only 20% to 30% of people being infected. Because of course another additional 30% of the population who has not been infected may very well have T-cell immunity. This obviously remains to be seen and is purely speculative at this point.
Thanks for joining me today on Medicine with Dr. Moran. If you've enjoyed this please give me a like. Always feel free to comment. Remember that with any infection or disease being healthy is the key to fighting it off successfully.
A good diet, regular physical exercise, good sleeping habits, and avoiding those bad habits such as smoking, or too much alcohol go a long way to keep your immune system and body in tip-top shape.
So remember, get healthy and stay healthy..