Wikipedia:Reference desk/Archives/Science/2020 March 11

= March 11 =

Why in USA it isn't recommended to put masks on?
Why in USA it isn't recommended to put masks on? (to avoid covid19) "As of February 26, 2020, face masks are not recommended for the general public in the US. Some health facilities require people to wear a mask under certain circumstances".ThePupil (talk) 02:28, 11 March 2020 (UTC)
 * The so-called experts are saying they are best used by the ones who are sick and by the ones closely caring for them. ←Baseball Bugs What's up, Doc? carrots→ 04:20, 11 March 2020 (UTC)
 * There is some logic to that. Whether it is the truth is another matter. There's no doubt that if you are spraying droplets of virus infested spit and phlegm around the place that wearing a mask will tend to catch some of the droplets. But I suspect the claim that healthy people do not reduce risks to themselves by wearing masks is driven more by hope and a wish to preserve mask stocks, than actual evidence. Of course providing masks to those who definitely need them, as opposed to a healthy individual, does have a benefit for the healthy, but it is a second order effect. Greglocock (talk) 04:27, 11 March 2020 (UTC)
 * Hence my use of "so-called". ←Baseball Bugs What's up, Doc? carrots→ 06:57, 11 March 2020 (UTC)
 * Health authorities in France, New Zealand, UK etc. all say there is no evidence that wearing a mask protects you (as in "there is no evidence that faith healing works" - "no evidence that" does not mean "we have not looked" but rather "we looked and found nothing but proving a negative is hard"). The possibility are hence
 * the advice is correct
 * the advice is wrong because scientific evidence is lacking
 * local health authorities are all incompetent and fell for WHO disinformation
 * local health authorities are all conspiring to lie to the public (and no journalist has found a whistleblower yet)
 * I have no idea how likely 1 or 2 are, but I am pretty damn sure that those are much more likely than 3 or 4. Tigraan Click here to contact me 08:42, 11 March 2020 (UTC)
 * I think 3 also requires a vast overestimation of how much the US CDC cares about what the WHO says. As I said below, IMO this also requires that we make assumptions that they were doing this long before the COVID-19 outbreak since the advice is consistent with that for seasonal influenza, or that COVID-19 is different and this is known but being ignored. Nil Einne (talk) 09:12, 11 March 2020 (UTC)
 * (EC) This discussion reminds me somewhat of the discussion a few weeks ago about whether COVID-19 is airborne. While COVID-19 is new, and there's still a lot we don't understand about it, as I understand it the general assumption is spread is likely to be similar to other respiratory diseases, albeit one with likely very limited immunity and where a lot about when, who and how easily it infects etc is still fairly unknown. (See e.g. [//www.washingtonpost.com/health/2020/03/10/face-mask-shortage-prompts-cdc-loosen-coronavirus-guidance/] for an example of uncertainty.) Therefore the face mask stuff tends to come back to what we know about their use with other respiratory diseases. And there seems to be little evidence that surgical type face masks worn by health individuals in public helps with such diseases, seasonal influenza being the obvious example. To be clear, this means there is an absence of evidence not that there have been good studies demonstrating they are not effective.  Many epidemiologists and others who study how such diseases spread, how to protect against them and observe human behaviour tends to believe they will be of little benefit in healthy individuals especially when many people don't know how to wear them correctly, may not change them frequently enough, etc. One of the most common suggestions is that they may discourage people from touching their faces but the counterpoint is that with at least some people they may actually do it more to adjust the mask etc. I think there is also a concern such masks may give a false sense of security and reduce compliance with good hand hygiene, which is believe to be of significantly greater benefit.  There seems to be some limited evidence of a benefit for correctly wearing such masks by healthy individuals when living in a household with an infected person and combined with good handwashing. [//books.google.co.nz/books?id=r05NkuhlVGwC&ots=JjuJTap47u&pg=PA51] [//bmcinfectdis.biomedcentral.com/articles/10.1186/1471-2334-12-26] [//annals.org/aim/fullarticle/744899/facemasks-hand-hygiene-prevent-influenza-transmission-households-cluster-randomized-trial] [//www.ijidonline.com/article/S1201-9712%2808%2901008-4/fulltext] [//journals.plos.org/plosone/article?id=10.1371/journal.pone.0013998] Possibly also when people are living in a crowded setting in general [//journals.plos.org/plosone/article?id=10.1371/journal.pone.0029744]. Note AFAICT, such studies generally did not find benefit for masks alone without handwashing, and they also generally included instructions etc on mask use. These studies are also I think, taken as evidence that such masks may be of benefit to protect health care workers who may regularly be coming into contact with infected individuals. (And are already supposed to be practicing good hand hygiene.)  It's worth noting that while the current situation may be somewhat unprecedented, if we get back to the earlier point, it isn't completely unique. If health authorities had good reason to think healthy individuals wearing masks in the general public would have a significant benefit for regular seasonal influenza, there's a good chance it would have been recommended by at least some, since there's no reason why supply couldn't have been adapted to cope with the demand. Possibly even during something like the emergence of H1N1, supplies could have coped with demand. In addition, it's likely at least some working on pandemic planning would have recommended more massive stockpiling to to prepare for something such as this, if they felt their use among healthy individuals should be encouraged. Note that there are plenty who recommended, long before this outbreak, that people with symptoms of respiratory illnesses/flu should wear masks as is common in a number of Asian countries.  See e.g. [//www.fhi.no/en/id/influensa/seasonal-influenza/influenza_advice/Not-recommended-to-use-face-masks-outside-healthcare-service/] [//www.cdc.gov/flu/professionals/infectioncontrol/maskguidance.htm] [//www1.racgp.org.au/newsgp/clinical/australians-with-flu-like-symptoms-should-use-mask] [//www.cnbc.com/2020/02/04/coronavirus-who-on-the-lessons-learned-from-the-sars-epidemic.html] [//www.forbes.com/sites/tarahaelle/2020/02/29/no-you-do-not-need-face-masks-for-coronavirus-they-might-increase-your-infection-risk/] [//time.com/5794729/coronavirus-face-masks/] [//jamanetwork.com/journals/jama/fullarticle/2762694] [//www.mayoclinic.org/diseases-conditions/swine-flu/expert-answers/flu-mask/faq-20057878]  As a final point, having sort of an interest in medical and health topics for a while, one thing I feel a lot of people don't appreciate is that in reality, a lot of what we believe and is put into practice is not based on particularly strong evidence. The relationship between diet and acne is perhaps a classic example of this. A loosely related example is there's always been controversy and recently been a strong move against antibacterial soaps based on the lack of evidence of any real benefit, and fears of possible harm from their widespread use. But I also came across this interesting example when searching this answer [//www.healthypeople.gov/2020/tools-resources/evidence-based-resource/gloves-gowns-and-masks-for-reducing-the-transmission-of].  Nil Einne (talk) 09:12, 11 March 2020 (UTC)
 * Off-topic but: a lot of what we believe and is put into practice is not based on particularly strong evidence - That is true of science in general. A standard experimental paper (at least in physics) will contain "methods", "results" and "analysis" sections; usually you can trust that if you follow the steps of the "methods" section you will end up with what was described in the "results" section, but "analysis" is often a pompous word for "we scratched our heads trying to figure it out, here goes the least crazy of our hunches". Of course in medicine there are additional ethical problems. If people are dying left and right from an epidemic, you might want to aggressively test highly-speculative remedies, whereas in physics, you can almost always wait for more confirmation.
 * The experimental method is still the best way we have found for figuring out things, but our state of knowledge about the world is a lot a shades of grey between "we know for sure that thing" and "we have no idea whatsoever to explain that thing". Tigraan Click here to contact me 13:28, 11 March 2020 (UTC)
 * (EC) One additional point. It's possible that some feel based on available evidence and understanding, healthy people wearing masks has a greater chance of being beneficial than of causing harm. Even after consideration of the relative risks and level possible of harm and benefit. This evaluation would likely be based both on the possible benefits of reduced transmission to said healthy people, and also reducing transmission from people who think they are healthy but aren't. (But also considering the chance it may increase transmission due to people adjusting their masks, masks collecting contaminants, a false sense of security, distracting from hand-washing advice etc.) So the precautionary principle would suggest healthy people should be encouraged to wear masks. But this isn't being happening due to a recognition supplies cannot cope with it and so they need to be reserved for those cases where the chance of benefits is far greater. (And it doesn't happen for seasonal influenza given factors like the low estimation of possible benefit, possible differences in number of carriers and people at risk of infection, limited number of people who may follow such advice and additional confusion and uncertainty that may result.)  However this is a fairly different issue from suggesting authorities are being misleading about the evidence. Although such views could be one the reasons why some authorities require mask wearing even for healthy individuals e.g. I believe in HK and some  other countries it's required to ride on their mass transport systems. (But there are other factors that may be at play e.g. the difficulty of enforcing a requirement to wear masks on people who know they have symptoms of a respiratory illness, compared to simply requiring it from everyone.)  Nil Einne (talk) 13:50, 11 March 2020 (UTC)
 * The advice not to touch your face and to wash your hands is probably also not based on experimental evidence of its efficacy, but nevertheless appears sound if contact transmission from touching contaminated surfaces is a major factor in spreading the infection. If it is the major pathway, then wearing a mask is probably not going to help much more in reducing the spread. It is also plausible enough that reusing masks may even increase the wearer's risk. I'd be surprised though if wearing proper and regularly changed masks would not prove to somewhat reduce the risk for someone who meticulously follows the other WHO advice. --Lambiam 14:01, 11 March 2020 (UTC)
 * Yes, this is important for such public health advice. Surgical masks only work when you wear them properly and change them regularly and properly. If people don't don't do this they're useless, and may be worse than useless because they may cause people to feel a false sense of security and hence not follow other advice (risk compensation). When evaluating interventions that people perform themselves we have to look at differences between "perfect use" and "typical use". (This is relevant for many interventions, for example birth control methods.) --47.146.63.87 (talk) 03:59, 12 March 2020 (UTC)
 * What I always heard about surgical masks is they help prevent you from infecting other people (e.g. by coughing: the mask stops the droplets). They don't stop the other people from infecting you, i.e. airborne viruses travel right through it.  They help you stop touching your face with your hands though, something I do all the time out of habit.  2601:648:8202:96B0:54D9:2ABB:1EDB:CEE3 (talk) 05:09, 12 March 2020 (UTC)


 * Short answer: They don't need it. There is a limited supply of masks, and we want them on the people who are coughing and sneezing. For all others, be careful and clean with your hands, and expect to get this cold eventually no matter what masks you are wearing, but be careful and clean so that those of us who must seek hospital care have space to do so. ~ R.T.G 18:22, 15 March 2020 (UTC)

COVID query
If this coronavirus spreads around the world, and it seems like it most certainly will, will it just disappear then? Is this virus set to be a new recurring incurable disease among humans as more familiar flus are?

This question doesn't seem to be asked a lot. People are more worried about dying today... However, influenza, which COVID is being called though it apparently is not, mutates at a rate which prevents it being cured by vaccination, or something like that, hence the new concoction yearly in the flu jab... I understand from reading about tundra that the deadly "Spanish Flu" has been detected in bodies thawed from the permafrost such that it is a concern among archaeologists and palaeontologists finding remains in the arctic circle. I also am led to believe that bubonic plague persists, even in America... So what is the outlook here? I'm not going to say "if" it is beyond our control. Will COVID persist as an irritant? As a deadly disease? Will it disappear? Expectedly, I cannot seem to find this enquiry in the new reports... without digging ten feet into muck which I've already turned over several times.

Any response appreciated, thank you, ~ R.T.G 16:45, 11 March 2020 (UTC)
 * Coronaviruses were first discovered in the 1960s, so they're obviously not going away anytime soon. ←Baseball Bugs What's up, Doc? carrots→ 17:00, 11 March 2020 (UTC)
 * To be clear, the virus that causes CoVID-19 is the same species as SARS, the same family as some common cold viruses but a completely different order from influenza virus. Not closely related. Rmhermen (talk) 18:05, 11 March 2020 (UTC)
 * You meant "group", not "species", which has a very specific meaning in biology. (The concept of a species is not really well-defined for viruses anyway.) --47.146.63.87 (talk) 07:00, 12 March 2020 (UTC)
 * My apologies! I see from the article that it was recently classified as the same species. I had read earlier that it was simply classified as "related". --47.146.63.87 (talk) 19:27, 12 March 2020 (UTC)
 * Well, Wikipedia says there is a plague season in Madagascar! As often with texts about infectious diseases, the truth is a good bit less disturbing than the headline, but the headline is not wrong. I'll point out that we don't worry too much about the plague and that may not be a reckless judgment. If you're look for a book about this sort of thing, I recommend David Quammen's Spillover. 93.136.81.202 (talk) 03:07, 12 March 2020 (UTC)

Bubonic plague (caused by Yersinia pestis) is definitely still around, but it's not that big a public health problem today, since it can be slowed down with hygiene and treated with antibiotics, neither of which were available (much) back in the middle ages. Covid-19 does seem to be able to survive in air "up to 3 hours post aerosolization". There are a bunch of temporary measures announced like closing schools for the next 2 weeks, but if anything the pandemic will be even worse 2 weeks from now than now. Better start stockpiling loved ones ahead of the outbreak. 2601:648:8202:96B0:54D9:2ABB:1EDB:CEE3 (talk) 04:18, 12 March 2020 (UTC)

Maybe, maybe not. We don't do predictions on the ref desk, and predictions at this point are going to be very uncertain. If we can control its spread, we might be able to contain it eventually, and then it will just "burn out" if it's unable to infect anything new. Plague is an example of a "direct zoonosis". It can infect numerous species as-is, so it circulates in natural "reservoirs" of animals, and can infect humans from there. To eradicate it we would have to immunize, kill, etc. all infected animals. But there is no sustained human-to-human transmission. Influenza is a whole big family of viruses that circulate in numerous strains among different species and, as you noted, mutate rapidly (because they're RNA viruses), which is why it's such a nasty thing to get a handle on. Smallpox and rinderpest, the two diseases we've eradicated, were eradicated with mass vaccination; the latter only affected various large mammals, which can't travel long distances easily, another helpful factor. However, we're still cursed with the descendant of rinderpest: measles. --47.146.63.87 (talk) 07:00, 12 March 2020 (UTC)

There was a reddit ama yesterday by an NHS critical care doctor that has what looks like good info: 2601:648:8202:96B0:54D9:2ABB:1EDB:CEE3 (talk) 09:51, 12 March 2020 (UTC)

flowers with 2 differnt sexes and with one sex
How do I find a list of flowers that have 2 different versions (male and female)? How do I a list of flowers that have only one versions (which is both male and female)? In the first case I want to find pictures of each of the versions.

Thanks a lot, Rami (talk) 19:33, 11 March 2020 (UTC)
 * Plant reproductive morphology looks like the starting place you want. Most flowers are "perfect", having both male and female sex organs, so a list of the latter will be most flowering plants. --47.146.63.87 (talk) 04:02, 12 March 2020 (UTC)