Severe Acute Respiratory Syndrome (SARS) and COVID-19 – Coronaviruses

00:00 Coronaviridae. The coronaviridae are large, enveloped, and intracellular membrane helical capsuled viruses. They have a linear single strand positive-sense RNA genome. So again, as a positive-sense RNA their genome can function as a messenger RNA. Transmission of these viruses is fecal oral but also sometimes by respiratory droplet especially for upper respiratory type illnesses. There are medically important or relevant species which we talk about. One is the severe acute respiratory syndrome virus otherwise known as SARS by its initials, SARS virus. And then the coronaviruses themselves which are a frequent cause of respiratory and some gastrointestinal disorders. Unfortunately, we now need to add a 3rd relevant virus.

00:54 SARS Coronavirus 2 which has been causing severe disease outbreak stemming from Wuhan, City, China. The transmission electron micrograph in front of you is showing typical appearance of, in this case, an animal strain of coronavirus and you can see that they have an almost pedicle arrangement around the outside of the membrane itself. So, the first and most common medical illness associated with the coronaviruses is the common cold. Incubation period 3 days, so very short. It is very common. In fact, it is probably as common as an enterovirus or a rhinovirus. Prognosis, fabulous unless one has a man cold hahaha, but it is a very common and very rapid resolving upper respiratory tract illness. Patients have the typical sneezing, rhinovirus, headache, sore throat, malaise, sometimes if fevers are high enough to also have shaking chills or rigors along with them. But it's mostly pediatric age patients, infants, and children who are exposed to this and again it's probably because the infectious particles are very readily available through respiratory droplet which deposits on horizontal surfaces. Children explore the world through their hands and their mouths. So, respiratory droplet or fecal oral transmission and you can see why the coronavirus is such a common cause of the common cold. Gastrointestinal tract infections are far less common especially due to coronaviruses but when occurring they also have a very fast incubation period up to 3 days. Prognosis super for this as well. It's a very mild version of what are sometimes very severe gastrointestinal infections caused by other viruses. In this case, diarrhea, gastroenteritis causing inflammation of the gut with a mild or nonspecific abdominal pain rarely some vomiting associated. The one associated medical illness which is quite severe which may be triggered by a gastrointestinal coronavirus would be a neonatal necrotizing enterocolitis. That is where the lining of the gut becomes inflamed perhaps initially due to the coronavirus but then due to innocent bystander damage sort of secondary attack by the immune system in an uncontrolled setting the gut lining that the enteric mucosal cells are destroyed allowing leakage of blood, pus, etc. that is a very dangerous process which can be triggered among other things by the coronavirus. And then last but not the least, the SARS virus is a severe acute respiratory syndrome virus. This at least, at the time of this recording, is now a historic event having last occurred in any significant fashion in 2003. The incubation period for this particular virus was up to 6 days typically around 4 or 5 and thankfully worldwide is quite rare except when one was in the middle of an outbreak in Asia and allowing or waiting for patients to travel to all parts of the rest of the world. During that outbreak and subsequently these sporadic cases, there is about a 30% spontaneous resolution rate. The other 70% go on to progress to severe infection and of those 10% die typically from respiratory failure. The clinical manifestations start with a higher fever so above 100 degrees Fahrenheit approaching 38.5 degrees Celsius with associated myalgias, lethargy, cough, and a sore throat. The patients feel, again, like they have a severe flu-like illness. However, they go on then due to secondary immunologic reaction to develop primary attack within the pulmonary parenchyma and this leads to a very severe multilobar diffuse pneumonia with many times a superimposed bacterial pneumonia to even further worsen the process. And there is a new type of coronavirus. SARS Coronavirus 2 began to cause disease in Wuhan City, China in late 2019 with an initial limited cluster of cases associated with an open air live animal market. However, that initial small number of cases rapidly began to spiral along the same pathway as did the SARS Coronavirus with, at first, thousands and then tens of thousands of cases developing in China followed by sporadic cases throughout the rest of the world. This illness appears to be more contagious than the SARS variant but thankfully is less fatal in its outcomes. As of early February 2020, the total number of cases of the Wuhan variant almost 30,000 has far surpassed the total number of SARS cases. However, and again thankfully, the mortality rate so far has not mirrored that of the SARS outbreak. The clinical manifestations are still emerging as of the time of this recording, but appeared to mirror those just described for SARS; high fevers with temp just greater than 100 degrees Fahrenheit, myalgias, lethargy, and a respiratory illness with cough, shortness of breath, and associated dehydration. The incubation period appears to be roughly from 2-14 days and evidence of human to human transmission has been demonstrated. So far, a majority of the fatalities have occurred in adults older than 75 years old, but all age ranges have been affected and the available information about the scope of this illness is still emerging. So, this particular cluster of viruses under the coronavirus heading is most often the cause of common cold is a relatively minor or benign process, although very common and the only time we need to worry about this is if there's an outbreak of SARS virus or 2019 SARS Coronavirus 2 causing the Wuhan City, China outbreak or if one has a neonate which has been exposed to a gastrointestinal coronavirus.