Hacker News Reader

Comment by gzu | Hacker News Reader

It's really not hard to grasp why it would spread quickly. This virus harbors in the respiratory system of an infected patient. The viral infection invades cells and releases more of the virus.

This is so contagious because:

1. Everyone breaths in nearly 8000 liters of air each day

2. Virus are so small that they stay suspended in air for a while, some estimates are 30min (think how smoke stays afloat)

3. We have no innate immunity to this novel virus

View on HN

Article lists multiple leading experts working round the clock on this, all saying they're not sure why the virus is so contagious.

But some random person of uncertain credentials says "It's really not hard to grasp why it would spread quickly".

If you have some kind of expert credentials with serious evidence, then it would be great to hear it. Otherwise your opinions are just unhelpful, potentially dangerous noise - and the internet has no shortage of those already.

These experts are looking for the biochemical proof of why it's so contagious.

That's not needed to make judgements on why this virus could be spread easily.

What they're trying to figure out is how it spreads so quickly when other viruses of the same family do not. Also this is an RNA virus (like most viruses), and RNA is not a stable molecule, especially compared to DNA. The ability of the virus to attach to and invade cells is also not an absolute. Our adaptive immune system can and does recognize the virus as a threat. What you flippantly described as "not hard to understand" is actually very hard to understand for the domain experts actually working in this field..

Your points suggest that every respiratory virus should be highly contagious, but don't explain why this one is more contagious than other similar viruses.

This one is more contagious than a common cold?

It's more contagious than its close relative, SARS.

see point 3

I think 8,000 liters is a bit off?

2,113 gallons / 8,000 liters

1,849 gallons / 7,000 liters - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3357553/

2,642 gallons / 10,000 liters - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4398662/

2,642 gallons / 10,000 liters - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4448375/

3,000 gallons / 11,356 liters - https://www.nasa.gov/mission_pages/cloudsat/news/air-water.h...

3,963 gallons / 15,000 litres - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4398662/

https://www.google.com/search?q=site:ncbi.nlm.nih.gov+liters...

Yes, all good conjecture that is likely accurate, but wildly important to not only proceed based on these assumptions and to get definitive proof of the mechanisms

I'd bet by the time we get definite scientific proof of the mechanisms, the every city in the country will have outbreaks.

taking prudent measures and stating definitive truths are two entirely separate endeavors

4. Temperatures are ideal in the regions where it's spreading

It’s unclear how much this matters

So are temperatures in the human respiratory system. It’s foolish to just assume warmer temperatures will stop it.

Why is there so much general confidence warmer temps will reduce spread? Is it really warm temps = more daylight = more UV bouncing around breaking up virus particles in the air? Does it make any difference at all for the majority of folks who spend almost all waking hours inside?

I believe its something along the lines that when there is more moister in the air, the water droplets grab the floating particles and fall to the ground. Thus higher humidity often slows the impact of airborne virus, hence we have a flu season.

I think there's probably an aspect of wishful thinking, and I certainly wouldn't say that there's anything like general confidence in the idea. Actually, I've only heard this stated as fact by politicians and similar; experts are mostly WAY more cautious about it.

it is because the warmer weather is what stopped SARS-COV in 2002 from spreading this far. the western world was lucky in that ignoring it the first time was an okay strategy. SARS-COV-2 is making its way around the globe right now and hopefully has the same limitations or this may get out of control. ignoring is the most dangerous option at this point. please watch this video by 3blue1brown https://www.youtube.com/watch?v=Kas0tIxDvrg a math professor in the US about the situation.

But maybe the main reason that SARS died out by the summer was not primarily because of the temperature but had more to do with the fact that it wasn't as nearly contagious and they were able to contain it with social distancing?

I don't know if there is such confidence among specialists, but among non specialists the arguments I have heard are based on assumed similarities with the common flu. These arguments may or may not apply , and there is still disagreement and unanswered questions on why the flu is seasonal:

https://www.scientificamerican.com/article/why-do-we-get-the...

It's spreading in Australia where it's summer with cozy 30°C

85 cases in Australia. And how many of those are imported?

In a binary sense, yes it “is spreading”. Even an R0 of 0.1 is “spreading”. But there is hardly enough data to say it is spreading widely in Australia.

The virus spread in summer/tropical vs winter/non-tropical regions is orders of magnitude different. But this is also not definitively causal. Just extremely highly correlated.

Yup, the counter to it is India. With almost all of the 43 cases imported even after more than 17000 tests seem to indicate that it's not spreading there (it could be a variety of factors including under-testing).

Is there community spread in Australia at this point or are most of those cases imported or directly related to an imported case?

There does seem to be some secondary spread in Australia however this seems to be from close contact with people who have been overseas. We are a little late to the game having established effective screening and information sharing early On. There is a expectation that the next few weeks will show a marked increase in community spread.

Reply on news.ycombinator.com