# Do sunshine and fresh air kill viruses? **URL:** \ **Category:** The Quarantine Zone\ **Tags:** covid-quarantine\ **Created:** [March 15, 2020, 6:43am UTC](https://boards.straightdope.com/t/do-sunshine-and-fresh-air-kill-viruses/849523 "2020-03-15T06:43:37Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![nelliebly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nelliebly/32/5422_2.png) [@nelliebly](https://boards.straightdope.com/u/nelliebly)\ **Post date:** [March 15, 2020, 6:43am UTC](https://boards.straightdope.com/t/do-sunshine-and-fresh-air-kill-viruses/849523/1 "2020-03-15T06:43:37Z")
It seems like a whacky idea to me, but a friend sent me [this article](https://medium.com/@ra.hobday/coronavirus-and-the-sun-a-lesson-from-the-1918-influenza-pandemic-509151dc8065), claiming that Spanish influenza patients had a higher survival rate if they were treated outdoors. > [@](#): > > Put simply, medics found that severely ill flu patients nursed outdoors recovered better than those treated indoors. A combination of fresh air and sunlight seems to have prevented deaths among patients; and infections among medical staff.[1] There is scientific support for this. Research shows that outdoor air is a natural disinfectant. Fresh air can kill the flu virus and other harmful germs. Equally, sunlight is germicidal and there is now evidence it can kill the flu virus. Outdoor air is a natural disinfectant? Sunlight is germicidal? Color me skeptical. It’d be another 20 years or more before antibiotics became widely available; if fresh air and sunshine were effective, wouldn’t hospitals have adopted this strategy in the Twenties and Thirties? True, TB sanitariums kept windows wide open, but it certainly wasn’t the case for polio or other serious diseases, was it? So what’s the straight dope on this one? If I catch a virus, would lying around on my balcony cure me? ---
**Author:** ![steepone](https://avatars.discourse-cdn.com/v4/letter/s/977dab/32.png) [@steepone](https://boards.straightdope.com/u/steepone)\ **Post date:** [March 15, 2020, 9:06am UTC](https://boards.straightdope.com/t/do-sunshine-and-fresh-air-kill-viruses/849523/2 "2020-03-15T09:06:42Z")
Sunlight definitely kills some viruses but I couldn’t say whether the flu is one of them and it only kills them if they are directly exposed so it’s not going to kill viruses in your body I doubt if fresh air would have any direct effect but being out in the fresh air would probably mean you would be exposed to less secondary infections than you would be in a stuffy hospital ward with a dozen or so other patients ---
**Author:** ![GreenWyvern](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/greenwyvern/32/2834_2.png) [@GreenWyvern](https://boards.straightdope.com/u/GreenWyvern)\ **Post date:** [March 15, 2020, 9:26am UTC](https://boards.straightdope.com/t/do-sunshine-and-fresh-air-kill-viruses/849523/3 "2020-03-15T09:26:05Z")
References from the article: [The Influence of Simulated Sunlight on the Inactivation of Influenza Virus in Aerosols.](https://www.ncbi.nlm.nih.gov/pubmed/31778532) > [@](#): > > These results are consistent with epidemiological findings that sunlight levels are inversely correlated with influenza transmission [Roles of sunlight and natural ventilation for controlling infection: historical and current perspectives](https://www.journalofhospitalinfection.com/article/S0195-6701%2813%2900154-0/fulltext#sec6) > [@](#): > > Historical and recent studies suggest that natural ventilation offers protection from transmission of airborne pathogens. Particle size, dispersal characteristics and transmission risk require more work to justify infection control practices concerning airborne pathogens. Sunlight boosts resistance to infection, with older studies suggesting potential roles for surface decontamination. [The Open-Air Treatment of Pandemic Influenza](https://www.journalofhospitalinfection.com/article/S0195-6701%2819%2930153-7/fulltext) > [@](#): > > A combination of fresh air, sunlight, scrupulous standards of hygiene, and reusable face masks appears to have substantially reduced deaths among some patients and infections among medical staff. [The open-air factor and infection control](https://www.journalofhospitalinfection.com/article/S0195-6701%2819%2930153-7/fulltext) > [@](#): > > In the 1960s scientists involved in biodefence research developed a technique for measuring the effect of fresh rural air on airborne pathogens [6]. They found outdoor air to be far more lethal to them than indoor air; both during the day and at night. They used the term ‘open air factor’ (OAF) to describe the germicidal constituent in outdoor air that reduces the survival and infectivity of pathogens [7]. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [March 15, 2020, 5:01pm UTC](https://boards.straightdope.com/t/do-sunshine-and-fresh-air-kill-viruses/849523/4 "2020-03-15T17:01:28Z")
Although the most effective wavelengths for killing viruses (and bacteria, molds, and spores) are the ones around 260 nm, where the DNA absorption is highest (and absorption leads to the creation of thymine dimers and other such structures, leading to death of the micro-organism), the ozone layer blocks such wavelengths from sunlight. However, it has long been appreciated that direct sunlight also kills micro-organisms, if not as efficiently. Louis Brandeis might have meant the saying “Sunlight is the best disinfectant” metaphorically, but the saying wouldn’t even make sense unless it were also literally true. Florence Nightingale approved of the use of sunlight in cures, as did Neils Finsen in Denmark much later. Works on civil engineering from the late 19th century point out the value of exposing drinking water to sunlight. Such longer wave disinfection relies on a number of mechanisms, not all of them fully understood. One appears to be the creation of oxygenated disinfectants, another is creation of poisoning substances i the micro-organisms, while another appears to be a weakening of cell walls. Whatever the method, long-wave ultraviolet that does persist in sunlight and even violet light seems to have disinfectant action. So the answer to the “sunlight” part of the OP is definitely “yes”.\* I haven’t looked into the Fresh Air part, but my gut instinct thinks it is, as well. Any thing that disperses potential air-borne organisms and exposes them to both lower temperatures and that disinfecting sunlight sounds good. \*I just wrote up two articles about Finsen and his work on the healing power of sunlight (as well as its apparently deleterious effects – besides causing skin cancer – in some cases), but they haven’t been published yet. ---
**Author:** ![nelliebly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nelliebly/32/5422_2.png) [@nelliebly](https://boards.straightdope.com/u/nelliebly)\ **Post date:** [March 15, 2020, 5:40pm UTC](https://boards.straightdope.com/t/do-sunshine-and-fresh-air-kill-viruses/849523/5 "2020-03-15T17:40:07Z")
Thanks for the replies. It looks like there is some validity to the sunshine theory. So why didn’t hospitals adopt it sooner? I’ve read that in some hospitals, convalescent patients (and of course, they were generally hospitalized for much longer than today) were often taken to a sun room for a little while each day, but it doesn’t seem to have been done until the patient was over the worst of the disease or surgery. If sunshine is effective, why didn’t hospitals use sunshine from the beginning with all\* patients? I’m guessing antibiotics seemed like a better answer, but what about in the years before antibiotics? \*I’m assuming sunshine would help prevent or mitigate viral infections post-op.