COVID-19 or coronavirus disease
COVID-19 or
coronavirus disease discovered in 2019, is responsible for a global
pandemic. COVID-19 is caused by a virus called SARS-CoV-2, or severe acute
respiratory syndrome coronavirus 2, because it's genetically similar to
SARS coronavirus, which was responsible for the SARS outbreak
in 2002. Now coronaviruses that circulate among the humans are typically benign,
and they cause a quarter of all common cold illnesses. In COVID-19,
what happened is that there were coronaviruses initially circulating among
bats, which are a natural animal reservoir that seems to have mutated and
ultimately started causing disease in humans. The outbreak began in China but
has since spread around the world. As of April 1st, 2020, or roughly four
months into the outbreak, there have been over 903,826 confirmed cases of COVID-19,
And 45,335 deaths, resulting a fatality rate of approximately 5%. However,
current studies suggest that the actual fatality rate is likely to be lower,
around 0.7%. The reason for this is that there are a lot of undiagnosed COVID-19 cases,
which makes the actual number of cases go way up. Many of these are
asymptomatic carriers, according to the CDC. This is in as high as 25% of the
cases. And there are many lessons to be learned from how different countries
have responded to the disease. To explore that, let's use an epidemic curve,
which shows the number of new cases in a country seen each day.
Healthcare Capacity
Healthcare capacity accounts for things like the number of beds,
ventilators as well as the number of healthcare workers and resources like
personal protective equipment or PPE they have available. Usually, the
healthcare system is working near full capacity, so when a pandemic like COVID-19 breaks
out, even a relatively small increase in the number of patient can overwhelm
the healthcare system So the two strategies to tackle this problem is to
flatten the curve and raise the line. Flattening the curve is focused on
diminishing the total number of people that get sick and slows down the rate at
which new people get sick while raising the line helps to actually increase
healthcare capacity.
Strategies
Let's take a look at how different countries apply these two
strategies: starting with China, the first country to deal with COVID-19.
China informed the World Health Organization about COVID-19 on
December 31, 2019. A few weeks later, on January 24 China aggressively tried to
flatten the curve by placing a major lockdown on the Hubei province, and then
issued a similar lockdown on other regions within China. Authorities forced
residents to stay at home, except for essential activities like going to the
pharmacy or getting groceries. Non-essential businesses or schools were shut
down, public transportation was shut down, and roads between cities were
blocked off. Going even further, some communities enforce a system by which
there was only one entrance and exit, and everyone passing through was screened
for symptoms of COVID-19. If anyone in the community tested
positive, the entire community might be quarantined. In all, this affected 15
cities and about 57 million people. The measures were swiftly enacted and
strictly enforced, and 12 days later on February 15, the exponential growth
broke, and the number of new cases started to fall off. Meanwhile, given how
many cases they're already were at that point, China made efforts to raise the
line. They built multiple hospitals dedicated to COVID-19 patients, and
flew in doctors and nurses from less-affected regions of the country to staff
these hospitals, and kept them protected with well-designed PPE that covered
them from head to toe. By March, the economy began to return to normal, and
China was seeing more cases of COVID-19 from travelers
than from their citizens. Now, let's look at South Korea which took a slightly
different yet equally effective strategy, to flatten the curve, they
implemented mass testing that was free, easy, and accessible. They offered
drive-through testing stations where people were tested in their car. They also
had phone-booth-like testing areas where the person walked in, gets tested, and
walks out. South Korea was performing 15,000 tests per day and by March 20,
they had tested around 317,000 people out of a population of 51,000,000, which
works out to 1 out of every 162 people. Those who tested positive were either
sent to a hospital if their symptoms were severe or to a quarantine facility if
the symptoms were milder. At the same time, public health workers conducted
contact tracing for every case, to track down individuals that might have been
exposed to the virus. Because South Korea had such a thorough understanding of
who did and who didn't have COVID-19 and where they
have been, the lockdown was effectively done at the level of the sick
individual rather than at the society level like in China. Given the
fore-warning that South Korea had about the disease and the aggressive efforts
around case identification their healthcare system was well prepared for the
patients, and had the resources they keep the healthcare workers safe. Next,
let's look at the United States, which has the most cases in the entire world
and where the number of cases continues to rise quickly. In terms of testing,
based on March 20th data, the US lags behind with only 135,000 people tested
which works out to 1 out of every 2,424 people, roughly 15 times less than
South Korea, despite both countries having their 1st confirmed case
on January 19th, one in the state of Washington and the other in Seoul,
Korea. Unfortunately, the US data doesn't include testing done by
private companies, but as of late March, testing has been well-documented to be
woefully inadequate in most parts of the US, requiring days to get a result or
being unavailable altogether In addition to the absence of widespread testing
to identify which individuals need to be isolated, only some united states have
mandated a lockdown, and even when it's applied, there's been minimal
enforcement. So in sum, without a federal mandate or enforcement of a lockdown,
it's been largely a scattered state-by-state effort that has mostly been
voluntary. In terms of raising the line, healthcare workers have
generally had inadequate PPE, especially N95s, to feel safe; and as a result,
hundreds of physicians and nurses have gotten ill or being quarantined.
Meanwhile, intensive care units or ICU beds have started to run out. Ventilators
are expected to be in short supplies, and there have been runs on medications
like hydroxychloroquine. Unfortunately, in the context of having scarce
healthcare resources, we know that mortality rates can be quite high.
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| Complete lock down |
Complete lockdown
Now here's the good news, a complete lockdown meaning one that's
enforced rather than voluntary, so that the maximum number of people abide by
it can stop the spread of COVID-19 within a matter of
days, even in a country that had seen exponential growth like the US. To show
how this works, let's start with the community that's already seen an
exponential growth in COVID-19 cases. Most folks
with COVID-19 have mild symptoms, or have just gotten
it and haven't begun showing symptoms yet. There are two options at this point:
Option 1 is to let things continue with the voluntary social distancing policy
where some adhere to it while others can continue to throw pool parties, keep
businesses open and invite relatives over for dinner. And that scenario, even
with the best of intentions, and cleaning precautions over the next two weeks,
there's still going to be an exponential growth in cases. Causing hospitals to
fill up with patients and many people will die, but, now consider option 2: and
Option 2, there's an enforced lockdown with absolutely everyone confined to
their home. If that would happen, the virus could spread to household contacts
but after that, the transmission would abruptly end. As these infected people
recover, with no access to new hosts, the virus basically has no place to go,
and within two weeks, the number of new cases starts to fall. Fewer cases mean
that the healthcare system doesn't get overwhelmed, and the mortality rates
fall because everyone who needs care can get it. This approach and timeline is
based on real data from Hubei where they implemented option 2. The rate of new
cases decreased within a few days of lockdown and because there's a lag between
people getting sick and going to the doctor, that decrease will be seen about
two weeks later in terms of fewer new cases coming to the hospital. The bottom
line is voluntary social distancing is only as effective as the number of
people who are practicing it. If enough people don't adhere, then the virus can
continue to spread, and the pandemic drags out, ultimately resulting in more
deaths.
Mortality rate
Now in terms of mortality, the data shows that the COVID-19 mortality
rates differ by group so for example, if you split things out by age, you can
see from this table, that fatality rate is relatively low if you're below 60
with no deaths seen in children 9 and younger, but then it starts to really
climb up for the elderly. So, they are really the ones at the highest risk. Similarly,
the fatality rate is higher for folks with hypertension, diabetes,
cardiovascular disease, chronic respiratory disease, and cancer, relative to
folks without any of these conditions. And of course the elderly are more
likely to have a lot of conditions, so it's not surprising that they go hand in
hand. One other group is pregnant people, and the data has been sparse, but it
seems like healthy pregnant people, are not at high risk for developing a serious
disease, and to date, there haven't been reported cases of intrauterine
transmission of COVID-19. The virus also wasn't detected in
the breast milk of a small group of mothers with COVID-19.
And in terms of breastfeeding, the main risk would still be from droplets,
rather than through the milk itself. Now overall, based on the current data,
over 80% of the patients with COVID-19 have a mild
infection, and some people don't develop any symptoms at all. For others, they
can develop mild symptoms, like fever, cough, and shortness of breath.
Other symptoms
Other symptoms include fatigue, and things like loss of smell and
taste. Serious problems include pneumonia. And if there are severe lung damage,
that 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 bloods' organs starved for oxygen.
ARDS and shock are the main cause of death for people with infection. Finally,
it's worth noting that even folks that don't die from COVID-19 including
young and healthy individuals can go on to develop pulmonary fibrosis, a
chronic lung condition that can severely impair a person's quality of life. In
addition to causing disease, coronaviruses can spread quickly. It's
increasingly clear that a lot of the spread is occurring through presymptomatic
people, folks that are in the incubation period, many of whom are not at high
risk themselves. It also spreads from those with symptoms, like 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. Coronaviruses don't usually spread over long
distances in the air, but they can get flung from one person to another on tiny
droplets of saliva when someone's coughing or sneezing.
Recent studies suggest the SARS-CoV-2 airborne
droplets can remain infectious for up to 3 hours In addition, the SARS-CoV-2 virus
can also survive on surfaces, it can survive up to 8 hours on latex and
aluminum, up to 24 hours on cardboard, up to 3 days on countertops, plastic,
and stainless steel, and up to 5 days on wood and glass. So, make sure you
clean and sterilize frequently touched surfaces like phones, keyboards, door
handles, and toilet seats with alcohol-based cleaning wipes. Once a person is
infected, symptoms develop about 5 days later, this is called the incubation
period. Now there's a debate about how much asymptomatic people or
presymptomatic folks that are in the incubation period are spreading the
disease and it may be much more than what was originally thought. Viruses are
given a reproductive number, or R0, based on how quickly they spread. And
person-to-person transmission has been confirmed both in and outside of China.
An R0 of 1 means that an infected person passes it onto 1 new person; and R0 of
2 means that one person spreads to two people and so forth. So, if the R0 is
below 1, the infection peters out; if it's one, it stays steady. And if it's
above one, then it continues to spread, the current estimate for COVID-19 is
an R0 of 2.2. As a point of comparison, the R0 of the flu virus is
about 1.3, so COVID-19 spreads quite a bit more easily.
Diagnosis
To confirm the diagnosis, a reverse transcription-polymerase chain reaction or RT-PCR test can be done, which can detect very small amounts of viral RNA. It's worth mentioning, however, that early in the disease, the RT-PCR can often miss the infection altogether, meaning that it's not very sensitive. So, if severe pulmonary disease is suspected, a chest CT can be done to help detect the presence of a viral pneumonia. Next, newer rapid testing methods for COVID-19 can get the results within minutes. One of these is isothermal amplification which also checks for viral RNA. The other is rapid serological testing which checks for the antibodies created by the immune system to fight the virus. Since it's checking for the antibodies made by the body, it can detect previous infections even after the virus is gone. Finally, it's also important to look for other causes of similar symptoms, by doing things, for example, like a quick flu test or respiratory viral panel, to look for alternative causes of the symptoms. In terms of treatment, individuals with mild symptoms should isolated themselves at home, so they can improve with rest and fluids.
Treatment
For those with severe symptoms, treatment is focused on supportive
care, such as providing fluids, oxygen, and ventilatory support for really ill
people. There's early data showing that Remdesivir, an anti-viral drug
previously used against Ebola may be helpful. Other medications that have been
used to try to treat severe COVID-19 include a
combination of Lopinavir and Ritonavir, both of which are anti-retroviral
drugs, as well as Chloroquine and Hydroxychloroquine which are usually used to
treat malaria, with one trial showing the effectiveness of hydroxychloroquine and
azithromycin being used together. On March 22, the WHO launched a global mega trial to test some of these promising medications. Vaccines are also being
developed by countries around the world, and it's estimated that they'll be
available in 2021, all of these medications and many additional ones are being
studied more fully in randomized controlled trials to see if there's a safe and
reliable treatment that can be used. Alright, as a quick recap, 4 months after
the start of the COVID-19 pandemic, countries around
the world have had variant levels of success in containing the disease. This
is done by flattening the curve and raising the line. Some countries like China
and South Korea have decreased the number of new cases, while in the US, the number
continues to rise. A mandated lockdown at a federal level to enforce social
distancing and mass testing are key components to preventing the spread of the
disease. Or raising the line can be accomplished by training more frontline
healthcare workers building more hospitals, and providing hospital staff with
adequate PPE. Treatment is focused on supportive care, and a number of
medications are in clinical trials. And there may be vaccine ready in 2021. For
individuals, the best strategy is prevention; this includes staying isolated,
careful handwashing, and avoiding touching your T-zone; if you're a healthcare
worker, you should use personal protective equipment.
