How does the Wuhan coronavirus spread?

DISCLAIMER: I am not a doctor or a virologist or any other occupation that would give me job-related expertise.

The new coronavirus spreads very much like the flu does. There can be the impression that it’s some sort of super contagion but there’s no evidence of that. It’s not like someone with the virus gets on a plane, and then when the plane lands everyone on the plane has the virus. In fact, I don’t know of any confirmed cases of transmission that happened on a plane flight (although I could be wrong).

I think there are five reasons why this virus has a higher R0 than seasonal flu:

1. An infected person can be contagious for a very long time. It’s believed that the virus can be contagious before even the appearance of symptoms, and in the case of severe infections, it can be three weeks between first symptoms and release from a hospital or death. That’s a long time for the virus to infect people, especially medical workers who aren’t taking precautions because they don’t know that their patient has the virus because the patient was never tested.

2. Some (many?) people who get the virus are asymptomatic or minimally symptomatic but are still contagious. They have no reason to think they have a serious infectious illness and need to stay home, nor do the people who come in contact with them have reason to avoid them. Patient 1 in northern Italy caught the virus from patient 0 who never had any symptoms except for mild cold symptoms for only one day. [UPDATE: Italian health officials have no idea where patient 1 caught it from. They tested who they thought was patient 0 for antibodies to the virus and found none.]

3. Foodborne and fecal transmission. I think that, compared to seasonal flu, this virus is more easily caught by eating food prepared by someone who has the virus. I suspect that’s how it spread through the cruise ship, and NOT through the air circulation. There is a scientific paper supporting the idea of fecal to oral transmission. This also suggests a possible transmission vector from sitting on a public toilet and flushing it, which could spray virus up your anus or into the air.

4. Many people have some level of immunity to seasonal flus because they’ve had a similar flu in the past or had a flu vaccine, but no one has any immunity to the new coronavirus.

5. Super-spreaders, people who shed more virus than most people, seem to be responsible for a disproportionate number of transmissions. I don’t know if this also happens with influenza, but perhaps the super-spreader phenomenon is more pronounced with coronaviruses. The super-spreader phenomenon was observed with previous coronaviruses (MERS and SARS).

For the reasons above, people who believe the virus will magically disappear when the weather gets warm are just deluding themselves. The contagiousness could go down a bit during warmer weather, but the virus will still be contagious enough to continue to spread unless we impose society-wide efforts to increase social distancing.

As for practical advice, the best way to avoid catching this is the same as the best way to avoid catching any other type of upper respiratory infection. Keep your distance (3 feet minimum, ideally 6 feet) from people who are infected. And because you don’t know who’s infected, keep your distance from everyone. Plus good hand hygiene.