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  • Since its debut in December 2019, we've been hit with a deluge of information about

  • the novel coronavirus that has often made it difficult to separate fact from fiction.

  • And that's because with each day, we're learning more about the virus behind this global pandemic.

  • As new data has radically altered the scope of COVID-19, we wanted to take this chance

  • to cut through all the misinformation and take a closer look at what exactly it is,

  • the latest info about how it attacks our bodies, and how its stealthy nature has completely shut down our world.

  • We haven't been in a situation like this in over 100 years.

  • No one has experienced a virus that's had this combination of ease of transmissibility and mortality.

  • I'm Timothy Brewer.

  • I'm an infectious disease doctor and professor of medicine and epidemiology at UCLA.

  • I've been an infectious disease physician for about 30 years and an epidemiologist for 25.

  • Known for the spike proteins on their surfaces, coronaviruses are a large family of viruses

  • that can cause respiratory illnesses like the common cold and more severe ones like

  • SARS, MERS and of course, COVID-19.

  • And here's what we know so far about what the virus does to your body.

  • Once it enters the respiratory tract through the nose, mouth, or eyes, it attaches itself

  • to the surface of a cell likely via a receptor called ACE2.

  • The virus then fuses with the cell's membrane, and releases its RNA.

  • The infected cell then begins to make copies of the virus that will continue their invasion throughout the body.

  • But when it comes time for the immune system to fight back, it's a bit of a mixed bag

  • when it comes to the human body's response.

  • While the majority of cases are mild,

  • Severe disease occurs in about 15% of individuals, and about 5% of individuals are so sick that

  • they need to go into an intensive care unit and probably end up on a ventilator.

  • Now keep in mind, most of the statistics we have come from a study of roughly 72,000 COVID-19 patients in China.

  • In this study and others since, severe cases displayed an intense cough, high fever, shortness

  • of breathand in some cases, pneumonia.

  • In the more extreme cases, there has been increasing evidence that patients' immune

  • systems are overreacting to the virus in a specific way.

  • So the cytokine storm are the chemical signals that the immune system is releasing to basically

  • call out all the forces to try to eliminate the virus.

  • And in the process of doing that, they can also damage normal cells like cells in the

  • lung that make it difficult or impossible for the individual to breathe.

  • And since our organs need oxygen to function, complications from the disease can lead to organ failure and even death.

  • And if you still think that these severe cases only affect the elderly or those with pre-existing

  • conditionslike diabetes, heart disease or asthmathink again.

  • Recent CDC data reported an increased number of hospitalizations among healthy adults in

  • the U.S. between the ages of 20 and 54 years old.

  • Why one person will develop very severe disease and potentially die and another person not

  • is not entirely clear, but it's probably genetically determined by small differences in the way

  • your immune system works and responds to a certain pathogen.

  • My name is Dr. Larry Lutwick.

  • I'm a professor of medicine at the Mayo Clinic, School of Medicine and Sciences.

  • I've been in infectious diseases for 40 some odd years.

  • Now for those who experience a milder form of COVID-19, diagnosis can be difficult to pin down.

  • Common symptoms include low-grade fever, fatigue, and a dry cough, but as we learn more about

  • the disease, there have been reports of a much wider and surprising array of effects.

  • A notable symptom that has occurred is loss of smell.

  • Why some people are presenting with diarrhea as the first manifestation?

  • Why some people, are presenting as if they're having a heart attack with severe chest pain without any cough at all?

  • Luckily about 80% of cases will experience this milder form of the disease.

  • But what makes COVID-19 so mysterious is that its milder cases can look like the common

  • cold or the flu or even go completely unnoticed.

  • What we're learning from COVID-19 is that individuals are infectious, before they

  • have any symptoms like fever, cough, or sore throat.

  • An asymptomatic case is someone who would test positive without ever developing symptoms,

  • while a pre-symptomatic case would test positive before developing a cough or a fever.

  • That is….if we're testing at all.

  • In COVID-19's case, preliminary data out of Singapore suggests that presymptomatic

  • cases are contributing to the spread of this disease, while here in the U.S., the head

  • of the CDC recently suggested that asymptomatic cases could make up as many as 25% of the total infections.

  • But because the person has no symptoms, they don't realize they shouldn't be going out,

  • they shouldn't be interacting with others.

  • And that stealthiness of it, the ability to transmit without symptoms, is part of what

  • is causing this pandemic to occur.

  • There are data to show that even before individuals have symptoms there's a lot of virus in the body.

  • What we call a high viral load.

  • And the more virus there is in the body, the more easily that virus can be generated in

  • droplets and spread to other individuals.

  • That's part of why testing is so important.

  • Right now, it's believed that it takes on average 5-6 days after exposure, and sometimes,

  • up to 14 before symptoms begin.

  • So that's why measures like social distancing and hand washing are so crucial to stem the

  • spread of COVID-19, especially when you're dealing with a virus that has a higher rate of transmission, or “R nought,” than the flu:

  • Influenza is typically a little bit more than one.

  • Based on early studies, the R nought reproduction number for COVID is about two and a half.

  • So for every one person infected, somewhere between two to three new infections incur.

  • COVID-19's stealthy nature makes it unlike anything we've ever seen.

  • And we know that with all the information out there, it can feel overwhelming.

  • But from vaccine development to antiviral therapy to advanced contact tracing and testing

  • strategies, the world at large is better scientifically equipped than ever before.

  • It might take a little while, but we can tackle this unprecedented challenge, and it all starts with you.

  • There's nothing easy about a pandemic.

  • The hardest thing, I think, for health care workers and people in general, is the scope of the disease.

  • Society is not used to something like that.

  • You have an active role to play by staying at home, by washing your hands, and by helping

  • other people to stay at home and be isolated if they're sick.

  • So I just want to thank everybody for doing their part to help us all get through this pandemic.

Since its debut in December 2019, we've been hit with a deluge of information about

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Why Is COVID-19 So Hard to Track?

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    Jerry Liu posted on 2020/04/28
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