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SARS-CoV-2 seems to hate both dryness and humidity. It thrives in mid-range humidity, particularly the chilly but not freezing environments.

This take has held up pretty well. Look at how much more mid-range NYC is humidity-wise than the others:

https://twitter.com/JeromeRoos/status/1236733607902937089



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Read this:

Stability of SARS-CoV-2 in different environmental conditions

https://www.medrxiv.org/content/10.1101/2020.03.15.20036673v...

Humidity has a tie to temperature and for this virus that seems to be the bigger "factor"


It seems that way. Here's another analysis of studies that focused on indoor humidity.

>"If the relative humidity of indoor air is below 40 percent, the particles emitted by infected people absorb less water, remain lighter, fly further through the room and are more likely to be inhaled by healthy people. In addition, dry air also makes the mucous membranes in our noses dry and more permeable to viruses," summarizes Dr. Ajit Ahlawat.

https://www.tropos.de/en/current-issues/press-releases/detai...

Actual paper:

https://aaqr.org/articles/aaqr-20-06-covid-0302


Just to be clear, that's about the original SARS, not the novel coronavirus (COVID-19 / SARS-CoV-2). I don't know of any studies about the effects of temperature and humidity on how long the current virus survives on surfaces.

> Plus it’s dry.

Some viruses, like flu, prefer dry air. That's actually the reason flu spreads better in winter -- because colder air is less humid.

https://news.yale.edu/2019/05/13/flu-virus-best-friend-low-h...


"The Effects of Temperature and Relative Humidity on the Viability of the SARS Coronavirus"

https://www.hindawi.com/journals/av/2011/734690/

"The dried virus on smooth surfaces retained its viability for over 5 days at temperatures of 22–25°C and relative humidity of 40–50%, that is, typical air-conditioned environments."


From TFA: "It's also fine in humidities above 98%, which you find in the rainy season in the tropics," she says, where the conditions outside resemble the environment the virus finds in the body.

What about humidity of the environment? Is that a reason behind the success of countries like Thailand, Vietnam in tackling Covid?

Possibly relevant study: https://www.annualreviews.org/doi/10.1146/annurev-virology-0...


There is abundant evidence that COVID-19 is affected by weather. [0] There is no evidence that the spread of COVID-19 is halted by weather.

[0] Google Scholar search of “COVID-19 humidity”


The suggestion that managing indoor humidity[1,2] (even hanging wet towels, as the author suggests) could improve covid resistance seems to make sense. Are there any covid-specific studies to support it?

[1] https://pubmed.ncbi.nlm.nih.gov/20815876/

via

[2] https://www.washingtonpost.com/opinions/2020/11/18/winter-co...


I thought humidity is what viruses hate.

Do high humidity levels decrease potency in case of Coronavirus?

Oh no, it's very humid.

The study uses relative humidity, which is affected by the dew point. While straight humidity is often consistent at least in the US, relative humidity fluctuates wildly. Relative humidity is what gives the muginess feel. Most of the US except the Rockies and most of the West Coast have way higher relative humidity in the summer months. NYC can get especially bad (or good in this case). In the South, that increase has already started.

Admittedly, it's not a huge affect, but taking your NYC example, the temperature alone will decrease the R0 by at least .5. I'll take that.


It's low humidit. You can read why on Wikipedia

Seems strange given the fact that I've seen numerous academic papers shared over the last few months indicating that hot weather and high humidity do indeed have some kind of effect on the virus's transmission.

Flu viruses don’t spread less when it’s warm. They spread less when it’s more humid.

For the northern hemisphere it’s much less humid in winter, but that’s not true everywhere.

https://www.livescience.com/27533-flu-transmission-humidity....

We really should be increasing humidity in hospitals and offices in the winter. Newer planes have already been moving in that direction (to increase comfort).


Thing is, it's almost always close to 100 % humidity when it's cold, since the air can hold so little vapor.

NYC isn't dry enough. This device operates through the evaporation of water. Using a humidity delta to create a temperature delta.

I've read several articles on this over the last few days. The consensus is that we don't know yet if heat and/or humidity reduce transmission of Covid-19 in any meaningful way. But it is certainly possible it will be suppressed in warmer or more humid weather as is the case for many similar viruses.
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