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Comment by raiyu | Hacker News Reader

Coronovirus has an rFactor of 2-3 and it is airborne, which requires droplets from a host to come in contact with an uninfected person. But these droplets travel to the air and then will collect on a surface. They will not stay suspended in the air. Simply breathing next to a person who has the virus isn't enough for transmission.

By contrast, measles has an rFactor of 17, because it is an aerosol. It is 6x more contagious. And as an aeorsol, simply breathing next to a person who is infected is enough for you to contract the virus.

Airborne is not the same as aerosol.

Put another way. If there is a person infected in a house hold with coronavirus, not everyone is guaranteed to get it, because it is only airborne.

If someone has the measles in a house hold, and there is no vaccine, then everyone will get it, because it is an aerosol.

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https://www.who.int/news-room/commentaries/detail/modes-of-t...

> In an analysis of 75,465 COVID-19 cases in China, airborne transmission was not reported.

"They will not stay suspended in the air" means it's not airborne. An airborne disease is one that does stay suspended in the air.

You have the terminology backwards. Coronavirus is not (epidemiologically) airborne, but it can be aerosolized and transmit through the air.

> Coronovirus has an rFactor of 2-3

It's recently been revised up to 5-6 [0], and mortality estimates reduced.

https://www.forbes.com/sites/tarahaelle/2020/04/07/the-covid...

R0 is environment specific and this number should be taken with a grain of salt.

The CDC paper [1] estimated that the R0 value may have been 5-6 in Wuhan, during lunar new year, and before the public was ware of the virus.

Alternatively, the R0 value is now <1 in the US and the spread is decreasing,

https://wwwnc.cdc.gov/eid/article/26/7/20-0282_article

We don’t know the R0 in the US yet. We need widespread testing that we don’t have to evaluate it.

Evidence out of NY today says it’s possible 14% of the state has already been infected. That’d point to a pretty high value.

https://www.wxxinews.org/post/random-test-finds-nearly-14-ny...

R0 is variable over time and describes the change in number of NEW cases.

IF new cases today are less than yesterday, the R0 must be <1 one incubation period ago. That doesn't mean that R0 wasn't different a month ago, or will be the same a month from now.

> IF new cases today are less than yesterday

That's a big if. We don't have enough testing in place to determine that currently. The reported number of cases and the actual number of cases are not the same right now.

We certainly have enough information now. You don’t need to know the total number of infections to know the trend.

Positive cases have stayed roughly the same since April 4th while testing increased. For R0 to be greater than 1, we would have to be worse at testing.

Testing has not increased. Look at the chart here:

https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/test...

(Direct link: https://www.cdc.gov/coronavirus/2019-ncov/images/lab-specime...)

We've been basically flat since mid-March.

Good point. I was mistaken.

I think the point still stands unless you think we are identifying a lower proportion of infections

> I think the point still stands unless you think we are identifying a lower proportion of infections

I do. https://www1.nyc.gov/assets/doh/downloads/pdf/imm/covid-19-d... indicates many areas of NYC are seeing more than 57% positive results; that likely indicates we're not even scratching the surface. We're simply not that good at identifying who to test.

considering the cdc's history on this (no masks!), I'd take anything they say with a grain of salt.

The estimated r0 of 2/3 is hilarious. less contagious than sars eh? No amount of down-voting me or cdc papers is going to convince me of that.

FYI. The 5-6 number is also from the CDC 0_0

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