DISCLAIMER: I am a general microbiologist, and not a SARS-CoV-2 expert. As you hear every institution saying during this pandemic, the situation is 'rapidly evolving', and there is SO MUCH we don't know about this virus. This post is meant to go over some of the basics to help you have a bit of a foothold when consuming information about this disease. I hope it's helpful. Also, this was written on February 20th, 2020.
If you want a little more background information on what coronaviruses are (because yes, there are lots of different kinds) and how this disease became a problem in the first place, then check out these two Instagram posts ( 1 and 2) where I walk you through the basics.
The condition caused by 2019 Novel Coronavirus is now officially being called COVID-19 (an abbreviation of ‘coronavirus disease 2019’). The actual virus itself is called SARS-CoV-2). It was first discovered in December of last year…so where are we now? The stats on diagnoses and ‘how many cases in which country’ are changing so rapidly that I want to instead focus on other important markers of this outbreak. (And yes, it has officially been recognized by the World Health Organization (WHO) as a Public Health Emergency of International Concern, or PHEIC—which sounds scary, but mostly speaks to how far it has spread).
Let’s take a look at the most important pieces of the puzzle:
How Does COVID-19 Make You Sick?
This disease is a virus, which means that (like other viruses) it gets its genetic material into your cells so that it can use your body’s cell division to replicate itself. As it multiplies, the virus is also destroying many of the cells it infects, effectively bursting those cells open. This is usually happening first in your upper airway, as most people are infected by exposure to the virus on their mouth or nose. Your body is trying to shed those cells as they die, meaning you are accumulating some dead tissue in the areas the virus is infecting. These are primary effects of the virus itself, but your immune system’s response is what can really wreak havoc. As your body sends immune cells to the heavily affected areas (again, primarily in your respiratory tract), you’re experiencing a highly inflammatory response—fever is a telltale sign of this process at work. If the immune response is particularly over the top, it can turn into what some physicians call a ‘cytokine storm’. Cytokines are a whole class of molecules released by your immune cells to get rid of infected or dead cells and regulate other immune processes, but if there’s a whole flood of them, lots of things can go wrong in your body and your organs may start to go haywire. While this is your body’s attempt to get rid of cells infected by the virus, it can also make swelling worse, which makes breathing even more difficult. As breathing gets harder and your lungs are put under more stress, other essential organs like your heart have to work even harder and may be over-taxed.
An important thing to remember is that everyone’s body will react to this infection differently. Health organizations around the world are still investigating why some people are severely affected by the disease and why some people experience mild symptoms and recover easily—but we have noted that there’s a strong correlation between fatal cases and those with compromised immune systems. That means that people whose immune systems are already weak—that can be the elderly, those with a chronic health condition that is already putting their body under stress, or those who are on an immune-suppressing medication for some other condition—these populations are especially vulnerable. Pregnant women may also be at higher risk of infection and mortality with respiratory infections like COVID-19, but no data specific to this disease has been produced yet in regards to pregnant women. Oddly, this outbreak actually seems to have a bit of a sex bias, with men being more severely affected than women. We don’t know why this might be, or if there is a biological underpinning to this trend or if some other confounding variable, like a social reason, could be behind this strange pattern. Children seem to be very rarely and very mildly affected, so it doesn't seem to be too dangerous for those under 12. Healthcare workers are also especially vulnerable to more severe infection because they are chronically exposed to the most symptomatic of the population, and may be directly exposed to the source of transmission (respiratory droplets) when they help patients who need respiratory support. Which brings us to...
How is It Transmitted? As I’ve covered in my previous social media posts about this outbreak, COVID-19 is a zoonotic disease, meaning the virus originated in non-human animals but is now able to infect humans. We still haven't pinpointed what intermediary animal originally transmitted the virus to humans, but the most likely original host for this coronavirus is bats. Bats most likely infected another animal in the wild that was then trapped and brought to a wildlife market where the virus was brought into contact with humans—some research has suggested pangolins, snakes, or civet cats as the potential intermediary host—but we still don’t know for sure. This outbreak is also capable of being transmitted from human to human. This is an important distinction. Some diseases that ‘spill over’ from animals can ONLY be transferred from their non-human animal host to a human—like Hendra virus, which humans can only catch from an infected horse. These kinds of outbreaks are easier to control than diseases that have adapted to be transmissible from human to human, because in the former case people will only get sick if they are exposed to the original source. With COVID-19 however, containment is complicated because people who are sick can pass the virus directly to other people. In this age of modern international travel, that means the disease can spread very far and very fast as people get on trains and planes, taking the virus with them all over the world.
To answer the question directly—you can catch COVID-19 by coming into contact with an infected human or animal, although it’s most likely that you would catch it from another human (and it’s unlikely that you would catch it from the original spillover source; i.e. a non-human animal). Infected humans can transmit the virus to those they come into close contact with, most likely through what the CDC designates as ‘respiratory droplets’. That’s the delightful wet spray that a sick person may emit from their mouth or nose when coughing or sneezing. Research is currently being done into how long the virus may be able to survive on surfaces that someone has coughed/sneezed onto, but it is currently thought that the MAIN and most common method of transmission is directly from human to human, not from touching a contaminated item or surface. We THINK people are the most contagious when they are the most symptomatic—that means that you are the most likely to catch it from an infected person when that person is experiencing the most symptoms, like fever, coughing, and sneezing. These symptoms can appear anywhere from 2-14 days after a person is originally infected.
Cases of asymptomatic people transmitting the disease to others have been reported, but research is still being done into how people are capable of passing on the virus when they are not exhibiting symptoms, and how common/likely it is. One of the tough parts about talking about all this is how much we still don't know! The way the disease has spread in Italy, Iran, and the US indicates that we still don't know the whole story about how people can catch the virus, so epidemiologists and other scientists are still exploring how long the virus can survive in the environment and how contagious people are at what stage in their illness.
What is Contagiousness? Let’s clear up some vocab that you might be hearing about in the news: Transmissibility from person to person is a disease’s contagiousness. This coronavirus is highly contagious—even more contagious than both SARS and MERS. That's how even though the mortality rate is lower than those diseases, COVD-19 has killed more people than SARS or MERS did. It's simply because COVID-19 has infected more people. How contagious a person is depends on their viral load—viral load is defined as how many viral particles there are per milliliter of sampled tissue or fluid. For many viruses, the higher a person’s viral load, the more contagious that person is—that is, the more likely it is that they can pass the disease to someone else. A person’s viral load is likely to be highest when they are the most symptomatic...although, again, lots of research is going on right now to determine if patients with COVID-19 can still be carrying a high viral load and shedding the virus when they are not symptomatic.
Will a Mask Keep You Safe? Regular masks, like the paper kind (‘surgical masks’) you can get at the pharmacy or the airport, do not actually do a whole heck of a lot to prevent you from GETTING sick. HOWEVER! If you yourself are sick, wearing a mask WILL limit the spread of YOUR infected respiratory droplets. So if you’re sick, you need to wear a mask. But if you’re looking to avoid becoming sick, the best way is to simply never touch your face (or really, any membranous orifices) with unwashed hands, practice correct hand hygiene (which is more intense than you’d think), and—surprise, surprise—avoid contact with infected people in the first place. For more in-depth coverage of mask effectiveness, check out this awesome video by my friend Trace.
What is the Mortality Rate? Mortality rates are a confusing statistic, especially if you’ve been hearing about so many deaths in China compared to deaths in other parts of the world experiencing the outbreak. That’s because this number is a worldwide average, AND an average across all demographics. In places with a very high density of confirmed cases, like in the epicenter of the outbreak in Wuhan, mortality may be significantly higher. This is because the number of patients who needed treatment quickly overwhelmed the availability of medical resources, so more people died than they would have had they all been able to receive prompt treatment. So the mortality rate is comparatively lower in countries with a higher ratio of medical resources to cases. Certain groups of people (the elderly, the immunocompromised) are also at much higher mortality risk, so the average mortality rate may not apply to you personally. While it’s good to always be brought back to reality, I’d also like to remind us all that just because 2% feels small doesn’t mean those deaths aren’t a big deal—they are. Every death is tragic, and the fact that preventable deaths are disproportionately affecting places that are having trouble responding to the density of cases should not be downplayed, and again, the mortality rate is higher for at-risk populations, so this overall average mortality rate can be a little misleading. ALSO mortality rates completely depend on how deaths are recorded, what the cause of death is reported as, how transparent a country is about their number, and how intense testing is: you can't record someone's death as COVID-19
Now, we can look at the mortality rate of the coronaviruses we’ve encountered in the past: the mortality rate for SARS is estimated to be about 15%, with very large variation from 0-50% depending on the affected population. Again, these averages don’t serve much of a purpose when considering an individual case because an individual’s response to the virus is affected by so many different things: genetics, age, immune function, access to medical care, etc. Coronavirus is more deadly than the common flu, but the common flu is much more, well...common.
What is Being Done by the Scientific and Medical Communities?
While all of the hubbub about the spread of the disease can be very scary and it’s certainly important to stay updated about what’s going on in your area, I like to focus on the incredible work being done by scientific communities all over the world to respond to the virus. Scientists in China shared the full genetic sequence of the virus soon after it was identified, and then labs worldwide—like at University of Texas at Austin and Lawrence Livermore National Laboratory —raced to model the protein structure of the virus. This helps researchers understand how the virus gloms on to a host cell and enters it or injects its genetic material into it. The parts of a virus that our immune system reacts to are called antigens, and a vaccine is treatment that prompts your body to recognize the antigen and swiftly induce an immune response before the virus can do too much damage. So protein modeling can also help us know what the antigen is and how we can develop a vaccine. Several companies and universities around the world—like Regeneron, Inovio, Sanofi, UNC, and others are already in preliminary stages of testing potential new drugs in animal tissues and working on vaccine development.
Vaccines are tough to develop in response to an outbreak like this for many reasons, but partly because they have to go through many stages of safety testing to make absolutely sure that it’s ok to use them in human patients—experts are saying that even with an accelerated timeline, it could take up to 18 months to arrive at a safe vaccine. By that time, the peak of the outbreak may be over and the disease may be contained. But it’s still very worthwhile to put all the time and effort into this research because if nothing else, it will provide a great base of knowledge and drug development for us to work from in the event of another coronavirus outbreak—we’re actually using lots of the research that was done into developing treatments for the SARS and MERS outbreaks to inform research and decision-making when developing solutions for COVID-19.
Data science advancements, high performance computing resources, and computational epidemiological models are also being used to predict how, when, and where the virus may spread so that public health organizations can be as prepared as possible. Read more:
How Can You Get Tested/Treated for COVID-19?
There is a test, developed by the CDC, that uses what we know about the viruses genetic makeup to conclude if a patient has been infected. However, some of the original tests were defective and provided inconclusive results, so the CDC is developing an updated round to send out to US states and international governments. Right now, most healthcare providers will diagnose you based on your recent travel history, personal interaction history, and set of presenting symptoms. While vaccine development is currently taking place, there is not yet any antiviral therapy available for those infected. Treatment is symptom-based, so clinicians respond to all of the ways your body could be reacting to the virus and make sure your body’s reaction is kept under control, supporting your vital functions (mostly supporting your ability to breathe, trying to lessen the stress on your heart, etc.).
What Else Can You Do?
If you have travel planned in the near future but are worried about infection, check with your home country’s governmental resources for advice on travel guidelines and restrictions. Listen to your public health officials if they are giving guidance on limiting exposure in your area and do your best to avoid anyone who is actively contagious.
In the face of public panic like this, we often see people reacting out of fear—and often in ways that revert to our implicit bias. Reports of racist attacks (verbal and physical) have experienced a huge upswing in the US, South Korea and many other countries all over the world. People’s fear and racism are causing anti-Asian sentiment that is not founded or necessary in any way, and I would ask you to be very conscious of your own feelings and behavior during this time. Act according to the facts, not fear-based racial profiling, and put your money where your mouth is. Many people are avoiding their local Chinatown or Asian-owned businesses even if there have been no reported cases in these areas, and this may be hurting your community’s economy! Show your support, check your assumptions, and be a good person. Read my friend Naomi’s post about it here for even more advice and info.
If you’re interested in learning more, I suggest these resources:
Washington Post:
How Coronavirus Kills National Public Radio:
Scientists Try To Pinpoint Animal Origins Of COVID-19 Washington Post:
Coronavirus outbreak edges closer to pandemic status Towards Data Science:
Behind the Coronavirus Mortality Rate Centers for Disease Control:
COVID-19 Prevention and Treatment New York Times:
The Coronavirus: What Scientists Have Learned So Far Centers for Disease Control:
COVID-19 FAQ Mayo Clinic:
Flu mask: Should I wear one? World Health Organization:
What's spreading faster than coronavirus in the US? Racist assaults and ignorant attacks against Asians Al Jazeera:
China coronavirus outbreak: All the latest updates Mayo Clinic:
Coronavirus: What it is, what you need to know The Lancet:
Statement in support of the scientists, public health professionals, and medical professionals of China combatting COVID-19 Science Magazine:
Scientists are racing to model the next moves of a coronavirus that’s still hard to predict Science Alert:
Breakthrough in Coronavirus Research Results in New Map to Support Vaccine Design Lawrence Livermore National Lab:
Lawrence Livermore researchers release 3D protein structure predictions for the novel coronavirus And if you have a spare hour and aren't too squeamish, I HIGHLY recommend listening to
this interview with David Quammen, a science journalist who wrote a great book all about zoonotic diseases.