COVID-19 (Coronavirus Disease 19) – causes, symptoms, diagnosis, treatment, pathology

COVID-19 (Coronavirus Disease 19) – causes, symptoms, diagnosis, treatment, pathology


By now you’ve probably heard of COVID-19,
or coronavirus disease discovered in 2019, which is responsible for a global pandemic.
Thus far the main country affected has been China, but it has spread to a number of other
countries around the world to a varying degree. The virus was initially referred to as the
2019-nCoV, or the 2019 novel coronavirus and was informally called “Wuhan coronavirus”.
The World Health Organization named the disease COVID-19 because it doesn’t refer to a geographical
location, an animal, a person or group of people – all of which can lead to stigma.
They also wanted to make it pronounceable and related to the disease – not an easy task!
The virus was officially named SARS CoV-2, or severe acute respiratory syndrome coronavirus
2, because it’s genetically very similar to the SARS coronavirus which was responsible
for…well the Severe Acute Respiratory Syndrome, or SARS, outbreak in 2002. So SARS-CoV-2 causes
COVID-19. Now, coronaviruses that circulate among humans
are typically benign, and they cause about a quarter of all common cold illnesses. But
occasionally, coronaviruses that circulate in an animal reservoir mutate just enough
to where they’re able to start infecting and causing disease in humans, if they’re
given an opportunity. In 2002 SARS was a coronavirus that hopped over from bats to civets, which
is a cat-like mammal; and then over to humans. And in 2012, there was MERS, which was a coronavirus
that hopped over from bats to camels a few decades ago and then circulated among camels
for quite some time before infecting humans. COVID-19 most likely also started with bats,
but this time the intermediate host was probably a pangolin, an animal that looks like a cross
between an anteater and an armadillo. That’s based on the fact that scientists identified
a coronavirus in pangolins that’s a 96% genetic match to SARS-CoV-2. Sadly, pangolins
are heavily trafficked around the planet, largely because people believe that their
scales have healing properties. Because they’re moved around the world rather than left in
the wild, there are ample opportunities for a coronavirus to go from a pangolin to a human. As of February 11, 2020, there have been 43,103
cases of COVID-19 and 1,018 deaths, with a fatality rate of 2.4%, according to WHO. The
vast majority of cases and deaths have occurred in China. For some perspective, the 2002 SARS
outbreak resulted in 8,098 cases and 774 deaths, so the fatality rate was around 9.6%. And
the 2012 MERS outbreak results in 2,494 cases and 858 deaths, bringing the fatality rate
to 34%. Finally, for the 2014 Ebola outbreak, which was not due to a coronavirus, there
were 28,639 cases and 11,316 deaths. The fatality rate was a whooping 40%! At a microscopic level, coronaviruses are
single strand positive sense RNA viruses with protein spikes on their surface that look
a bit like a crown under a microscope. In fact, “corona” is latin for crown. Besides
looking majestic, these spikes allow the virus to invade cells lining the respiratory tract
and lungs. After binding, the coronavirus enters and takes over the cellular machinery
to make more and more copies of itself so it can spread to the surrounding cells and
get into the mucus. Sometimes the infection is mild, and some
people don’t develop any symptoms at all. For others, they can develop symptoms that
can range from mild symptoms like fever, cough, and shortness of breath, all the way to serious
problems like pneumonia. Severe lung damage can cause acute respiratory distress syndrome,
or ARDS, which occurs when the lung inflammation is so severe that fluid builds up around and
within the lungs. The severe infection can cause septic shock, which happens when the
blood pressure falls dramatically and the body’s organs are starved for oxygen. ARDS
and shock are the main cause of death for people with the infection, and this is more
likely to occur in those over the age of 60, smokers, and people with previous medical
conditions like hypertension. In addition to causing disease, coronaviruses
can spread quickly. Usually the virus spreads when people cough or sneeze, and tiny droplets
containing the virus are released. These droplets can land on another person’s mouth, nose,
or eyes, and that allows the virus to enter a new person. Virus can also be found in a
person’s stool, and in rare situations coronavirus has been transmitted from one apartment to
another within a residential building. This was seen in the 2002 SARS epidemic. At that
time, faulty plumbing allowed virus-containing fecal matter originating from one person’s
apartment to drift from drainage pipes back up into fixtures like sinks and toilets within
other apartments in the same building. This created a terrible smell and allowed the virus-containing
droplets to deposit on bathroom surfaces, ultimately causing people in those apartments
to get ill. Something similar may have happened with COVID-19, and this is being actively
investigated. Once a person is infected, symptoms develop
an average of 5 days later. This is called the incubation period. However the incubation
period varies from person to person, and in some studies, the incubation period lasted
as long as 24 days! Now there’s debate about whether or not asymptomatic people can spread
the disease, because these people typically have low levels of circulating virus. But
even if they do, asymptomatic transmission likely plays a minor role in the overall epidemic.
Viruses are given a reproductive number or R-naught based on how quickly they spread,
and person to person transmission has been confirmed both in and outside of China. An
R naught of 1 means that an infected person passes it on to 1 new person, an R-naught
of 2 means that 1 person spreads it to 2 new people, and so forth. If the R naught is below
1, the infection peters out, if it’s 1 it stays steady, and if it’s above 1, then
it continues to spread. The current estimate for the SARS-CoV-2 R naught is between 2 and
2.5. Of course that’s an average, with some spreading the disease less, and others – called
superspreaders – spreading the disease at a much much higher rate. The exact cause of
these superspreaders is unclear, perhaps they are just in contact with more folks, perhaps
their bodies naturally shed more virus, or perhaps there’s some other reason altogether. To confirm the diagnosis, there should be
a real time polymerase chain reaction or rt-PCR tests, a quick test used in many labs and
hospitals that can detect very small amounts of viral RNA. Treatment is focused on supportive care – providing
fluids, oxygen, and ventilatory support for really ill people. There’s also some early
data showing that three medications are highly effective against SARS-CoV-2 in the laboratory
setting. These medications are chloroquine, an anti-malarial drug; ritonavir, an anti-HIV
medication; and remdesivir, an antiviral drug previously used against Ebola. Remdesivir
was given to the first US patient with COVID-19 on day 11 of his illness as he was clinically
worsening, and he began to improve the very next day. Large scale clinical trials using
remdesivir are already underway in China. Unfortunately there’s no vaccine currently
available to protect against COVID-19. At best, it looks like a vaccine will be many
months away. So the goal is to avoid human to human transmission, starting with isolating
people with COVID-19. Coronaviruses don’t usually spread over long distances in the
air, but they can travel roughly 3 feet or 1 meter from one person to another on tiny
droplets of saliva, which are produced when someone’s coughing or sneezing. In addition,
some strains of coronavirus can survive on surfaces for over a day. With that in mind,
if you’re a healthy person living in a non-outbreak area, the recommendation is to avoid travel
to disease outbreak areas, generally stay away from crowded places, and stay at least
6 feet or 2 meters away from anyone with symptoms. Wearing a surgical mask is not recommended
because the general risk of getting COVID-19 in these settings is so low. As always, careful
hand washing is key and it should be done with soap or alcohol-based hand sanitizers
and scrubbing. Also, avoid touching your eyes, nose, and mouth—this is the area, known
as your T-zone is a common entry point for viruses into the body. For healthcare workers who are around people
with COVID-19, the recommendation is to apply droplet and contact precautions. That includes
wearing personal protective equipment like a clean, dry surgical mask, gloves, long-sleeved
gowns, and eye protection like goggles or a face shield. When performing a procedure
that generates aerosol, like tracheal intubation, bronchoscopy, CPR, or noninvasive ventilation,
it’s important to wear a N95 respirator. This prevents 95% of the small particles,
like respiratory droplets, from passing through. To recap, the SARS-CoV-2 virus causes a respiratory
disease called COVID-19. The virus probably originated from bats, then went to pangolins
as an intermediate host, and finally to humans. The virus travels in respiratory droplets
and enters the body via the mouth, nose, or eyes. Once inside the body, it replicates
in the respiratory system, causing symptoms like fever, cough, and shortness of breath.
Some people might develop more dangerous complications like pneumonia, ARDS, and shock. Treatments
are focused on supportive care, but certain medications like Remdesivir are currently
in clinical trials. In the meantime, the best strategy is prevention — this includes careful
hand washing, avoiding traveling to disease outbreak areas and crowded places when possible,
avoiding touching your T-zone, and if you’re a healthcare worker to use personal protective
equipment.