If we assume that this virus is as infectious as the common cold, we can expect the infection rate within a household to be approximately 25% of contacts. That means that of the people you LIVE with, 25% will catch it from you.
50% infection rate in a large, distributed population like China would be very extreme.
Over any time frame, it's still quite extreme. To use influenza as a proxy, which has virulence comparable to the cold, the yearly incidence rate in China is <35 per 100,000. Even if this is a full 100x worse, we aren't even getting close to 50% infection rate over the season or a 6 month time frame.
This is all well understood, and studied in considerable depth.
The media overreaction is typical, but here at HN we are better than that and we should strive to rely on established science (where available). No need to throw out extreme or unreasonable numbers!
Of course in many ways they are different, but not in the important ones for this discussion.
I used influenza because it was convenient in terms of available research, I could grab in a minute or two, but I'm sure if you care to look you can find similar data for rhinovirus.
Rhinovirus and influenza have very comparable R0's. R0 is the epidemiological measure of the "contagion" factor of a pathogen.
We could try to make the comparison you are suggesting instead. But to make a valid comparison we need to consider:
Is influenza infectious for 10 days before any symptoms show?
How many people get the influenza vaccine each year? I.e. is there some herd immunity built up?
The symptoms of influenza are universally nasty for everyone infected. No one with the flu is walking around and going to work (if you think do then you don't have the influenza virus you have a cold). It seems that at least some people with this new corona virus just have cold like symptoms and therefore will not by default be self-isolating like people with influenza naturally do.
I'm not making anecdotal conclusions or assumptions about whether people walk around or go into work, I'm simply stating the facts here based on considerable research.
Influenza is a useful proxy for the cold, because we have plenty of data on influenza strains with R0 very close to the cold.
Perhaps the most contagious disease we've ever encountered, the measles, has an R0 around 18. Before the 1960's, when the vaccine was licensed, we saw incidence rates as high as the .8% range yearly for measles. That is 20x more than influenza, but still orders of magnitude short of the 50% number you threw out there.
The cold and influenza both range from R0=1.3, to perhaps 6 on the very high end of estimates. 50% just isn't reasonable by any measure.
As for comparisons to this nCoV, it's still very early days and there are many unknowns. Still, there is no evidence to support an R0 even remotely close to the measles. 50% simply isn't plausible or reasonable, based on everything we know about viruses and epidemics.
Those colds that you’re seeing represent common symptoms of many viruses (metapneumovirus, paraflu, influenza, rhinovirus, RSV, etc, etc ... and many of these have multiple subtypes which can be concurrently circulating). In other words, you’re noticing common symptoms not necessarily the same virus.
> Those colds that you’re seeing represent common symptoms of many viruses
And not just that. I have a septum deviation, so I basically have a runny nose all winter long, even though, most of the time, no viruses are involved.
It's worth fixing that, surgery has come a long way. I had it surgically corrected last year and the energy boost from better breathing while physically active, better sleeping, and the lack of annoying people with my snoring are well worth it.
Peak cold symptoms last about 3 days. I never said 50% of the population have the same cold at once. 50% catching it over a 6 month period is very reasonable.
If we assume that this virus is as infectious as the common cold, we can expect the infection rate within a household to be approximately 25% of contacts. That means that of the people you LIVE with, 25% will catch it from you.
50% infection rate in a large, distributed population like China would be very extreme.