00:00 - 00:03 In December 2019 the Chinese authorities

00:03 - 00:06 notified the world that a virus was spreading through their communities.

00:06 - 00:11 In the following months, it spread to other countries, with cases doubling within days.

00:11 - 00:16 This virus is the Severe Acute Respiratory Syndrome-Related Coronavirus 2

00:16 - 00:21 that causes the disease called Covid-19 and that everyone simply calls coronavirus.

00:21 - 00:26 What actually happens when it infects a human and what should we all do?

00:27 - 00:33 [Intro Music]

00:34 - 00:41 A virus is really just a hull around genetic material and a few proteins, arguably not even a living thing.

00:41 - 00:44 It can only make more of itself by entering a living cell.

00:45 - 00:47 Corona may spread via surfaces,

00:47 - 00:49 but it's still uncertain how long it can survive on them.

00:50 - 00:56 Its main way of spreading seems to be droplet infection when people cough, or if you touch someone who's ill and then your face,

00:56 - 00:58 say rubbing your eyes or nose.

00:59 - 01:04 The virus starts its journey here, and then hitches a ride as a stowaway deeper into the body

01:04 - 01:10 Its destinations are the intestines, the spleen or the lungs, where it can have the most dramatic effect.

01:10 - 01:15 Even just a few corona viruses can cause quite a dramatic situation.

01:15 - 01:19 The lungs are lined with billions of epithelial cells.

01:19 - 01:25 These are the border cells of your body, lining your organs and mucosa waiting to be infected.

01:25 - 01:31 Corona connects to a specific receptor on its victim's membranes to inject its genetic material.

01:31 - 01:36 The cell, ignorant of what's happening, executes the new instructions, which are pretty simple:

01:36 - 01:38 copy and reassemble.

01:38 - 01:46 It fills up with more and more copies of the original virus until it reaches a critical point and receives one final order,

01:46 - 01:47 self-destruct.

01:47 - 01:53 The cell sort of melts away, releasing new corona particles ready to attack more cells.

01:53 - 01:56 The number of infected cells grows exponentially

01:57 - 02:03 After about 10 days, millions of body cells are infected, and billions of viruses swarmed the lungs.

02:03 - 02:10 The virus has not caused too much damage yet, but corona is now going to release a real beast on you,

02:10 - 02:11 your own immune system.

02:11 - 02:18 The immune system, while there to protect you, can actually be pretty dangerous to yourself and needs tight regulation.

02:18 - 02:25 And as immune cells pour into the lungs to fight the virus, Corona infects some of them and creates confusion.

02:26 - 02:28 Cells have neither ears nor eyes.

02:28 - 02:32 They communicate mostly via tiny information proteins called cytokines.

02:33 - 02:36 Nearly every important immune reaction is controlled by them.

02:36 - 02:41 Corona causes infected immune cells to overreact and yell bloody murder.

02:41 - 02:49 In a sense, it puts the immune system into a fighting frenzy and sends way more soldiers than it should, wasting its resources and causing damage.

02:50 - 02:53 Two kinds of cells in particular wreak havoc.

02:53 - 02:58 First, neutrophils, which are great at killing stuff, including our cells.

02:58 - 03:04 As they arrive in their thousands, they start pumping out enzymes that destroy as many friends as enemies.

03:04 - 03:12 The other important type of cells that go into a frenzy are killer T-cells, which usually order infected cells to commit controlled suicide.

03:13 - 03:17 Confused as they are, they start ordering healthy cells to kill themselves too.

03:18 - 03:23 The more and more immune cells arrive, the more damage they do, and the more healthy lung tissue they kill.

03:24 - 03:30 This might get so bad that it can cause permanent irreversible damage, that leads to lifelong disabilities.

03:31 - 03:34 In most cases, the immune system slowly regains control.

03:34 - 03:40 It kills the infected cells, intercepts the viruses trying to infect new ones and cleans up the battlefield.

03:41 - 03:42 Recovery begins.

03:42 - 03:47 The majority of people infected by Corona will get through it with relatively mild symptoms.

03:48 - 03:51 But many cases become severe or even critical.

03:51 - 03:55 We don't know the percentage because not all cases have been identified,

03:55 - 04:00 but it's safe to say that there is a lot more than with the flu. In more severe cases,

04:00 - 04:05 Millions of epithelial cells have died and with them, the lungs' protective lining is gone.

04:05 - 04:13 That means that the alveoli - tiny air sacs via which breathing occurs - can be infected by bacteria that aren't usually a big problem.

04:13 - 04:15 Patients get pneumonia.

04:15 - 04:20 Respiration becomes hard or even fails, and patients need ventilators to survive.

04:21 - 04:26 The immune system has fought at full capacity for weeks and made millions of antiviral weapons.

04:26 - 04:31 And as thousands of bacteria rapidly multiply, it is overwhelmed.

04:31 - 04:36 They enter the blood and overrun the body; if this happens, death is very likely.

04:37 - 04:42 The Corona virus is often compared to the flu, but actually, it's much more dangerous.

04:42 - 04:46 While the exact death rate is hard to pin down during an ongoing pandemic,

04:46 - 04:51 we know for sure that it's much more contagious and spreads faster than the flu.

04:52 - 04:56 There are two futures for a pandemic like Corona: fast and slow.

04:56 - 05:02 Which future we will see depends on how we all react to it in the early days of the outbreak.

05:02 - 05:06 A fast pandemic will be horrible and cost many lives;

05:06 - 05:10 a slow pandemic will not be remembered by the history books.

05:10 - 05:15 The worst case scenario for a fast pandemic begins with a very rapid rate of infection

05:15 - 05:18 because there are no counter measures in place to slow it down.

05:18 - 05:20 Why is this so bad?

05:20 - 05:24 In a fast pandemic, many people get sick at the same time.

05:24 - 05:28 If the numbers get too large, health care systems become unable to handle it.

05:28 - 05:34 There aren't enough resources, like medical staff or equipment like ventilators, left to help everybody.

05:34 - 05:36 People will die untreated.

05:36 - 05:43 And as more health care workers get sick themselves, the capacity of health care systems falls even further.

05:43 - 05:49 If this becomes the case, then horrible decisions will have to be made about who gets to live and who doesn't.

05:49 - 05:53 The number of deaths rises significantly in such a scenario.

05:53 - 06:01 To avoid this, the world - that means all of us - needs to do what it can to turn this into a slow pandemic.

06:01 - 06:04 A pandemic is slowed down by the right responses.

06:04 - 06:12 Especially in the early phase, so that everyone who gets sick can get treatment and there's no crunch point with overwhelmed hospitals.

06:12 - 06:17 Since we don't have a vaccine for Corona, we have to socially engineer our behaviour,

06:17 - 06:22 to act like a social vaccine. This simply means two things:

06:22 - 06:26 1. Not getting infected; and 2. Not infecting others.

06:26 - 06:31 Although it sounds trivial, the very best thing you can do is to wash your hands.

06:31 - 06:33 The soap is actually a powerful tool.

06:33 - 06:37 The corona virus is encased in what is basically a layer of fat;

06:37 - 06:41 soap breaks that fat apart and leaves it unable to infect you.

06:41 - 06:47 It also makes your hands slippery, and with the mechanical motions of washing, viruses are ripped away.

06:47 - 06:55 To do it properly, wash your hands as if you've just cut up some jalapeos and want to put in your contact lenses next.

06:55 - 06:59 The next thing is social distancing, which is not a nice experience,

06:59 - 07:03 but a nice thing to do. This means: no hugging, no handshakes.

07:03 - 07:09 If you can stay at home, stay at home to protect those who need to be out for society to function:

07:09 - 07:17 from doctors to cashiers, or police officers;. You depend on all of them; they all depend on you to not get sick.

07:17 - 07:24 On a larger level, there are quarantines, which can mean different things, from travel restrictions or actual orders to stay at home.

07:24 - 07:28 Quarantines are not great to experience and certainly not popular.

07:28 - 07:34 But they buy us - and specially the researchers working on medication and vaccinations - crucial time

07:34 - 07:39 So if you are put under quarantine, you should understand why, and respect it.

07:39 - 07:45 None of this is fun. But looking at the big picture, it is a really small price to pay.

07:45 - 07:50 The question of how pandemics end, depends on how they start;

07:50 - 07:53 if they start fast with a steep slope, they end badly.

07:53 - 07:58 If they start slow, with a not-so-steep slope, they end okay-ish.

07:58 - 08:02 And, in this day and age, it really is in all of our hands.

08:02 - 08:04 Literally, and

08:04 - 08:06 figuratively.

08:06 - 08:09 A huge thanks to the experts who helped us on short notice with this video,

08:09 - 08:11 specially Our World In Data,

08:11 - 08:15 the online publication for research and data on the world's largest problems

08:15 - 08:17 and how to make progress solving them.

08:17 - 08:23 Check out their site. It also includes a constantly updated page on the Corona pandemic