I'm getting questions about well-meaning medical worker threads with strict instructions on mask-wearing, implying if you don't do everything right, you endanger yourself. That advice is very true for medical workers, but it's bit of misunderstanding of universal masks. Thread

First, medical workers have different requirements from masks. They're around sick people all the time and they are trying to protect themselves. Remember, viral load matters a great deal, hence tragic young deaths of health-care workers. Please read this. https://www.nytimes.com/2020/04/01/opinion/coronavirus-viral-dose.html

"As with any other poison, viruses are usually more dangerous in larger amounts. Small initial exposures tend to lead to mild or asymptomatic infections, while larger doses can be lethal." Medical workers are around enormous viral loads. Little room for error. But that's not all.

Goal of universal mask wearing is to stop asymptomatic, presymptomatic and mild cases from infecting *others*. It protects you some, too, but not as much as medical masks. Anyway, keep your distance! The goal of masks in medical setting is to protect the *wearer*! Big difference.

For example, we had SARS spread in clinical setting due to insufficient attention to PPE doffing safety. So, yeah, if you are around an enormously high virus load all day, with sick people coughing on you etc. and you touch the outside of your mask, oops. It really is a hazard.

So when well-meaning medical workers explain their own mask donning/doffing procedures to you, the regular person wearing maybe a cloth-mask (good for you!) or even a surgical mask or that N95 you had leftover and you're sanitizing/re-using, they are aiming at the wrong target

What should you do? Well, follow the advice to the best of your ability but realize that you're not in a biosafety lab. First, masks don't replace distance. They add to it. Second, pay most attention to taking them off correctly and immediately washing your hands. Most important.

While shopping with distance, if you accidentally touch the outside of your mask, should you rush to take it off under biosafety level 3 rules? No. Mask still protects *others* from your potential spread. Yeah your hand can carry some virus there but remember viral load matters!

So medical folks aren't wrong but not targeting correctly. Stay away from others when you go out for essential activity, replace especially cloth masks often (few hours max), be careful especially taking them off, handle them carefully and wash hands immediately. That's it.

Also, I have been wearing transparent gloves out since February (my students can laugh about me explaining them in class!) and I sanitize over them all the time. Basically, I am still trying to be careful and treat them like my hands, but they can handle a lot of hand-sanitizer.

Yesterday, I learned that maybe even half of shoppers in regular grocery stores were wearing masks here in Chapel Hill. I last went out a week ago, and it wasn't even 10%! I am thrilled that it's taking off so quickly. Hope everywhere else, too! Meanwhile, stay home if you can!

Btw I've seen ZERO evidence that incorrect mask wearing *increases* risks to regular people compared to NO MASKS. The One study that the faux experts go on and on about looked at cloth masks compared TO surgical masks IN hospitals. Uh, duh. Surgical mask > cloth mask for a nurse.

Like this piece in @washingtonpost. It's full of weird speculation, too little actual science plus wrong conclusions. We've had some amazing journalism and also terrible performance by some health/science reporters who seem utterly unqualified. https://twitter.com/Pinboard/status/1247033976239218688

What would you think about a safety "expert" who said, without any evidence, that helmet/seat-belts make bikes/car less safe because of overconfidence and thus maybe don't use helmet/seat-belt? That's how wrong those faux experts are. Disqualifying error. https://twitter.com/DaveM604/status/1247177638944182275

By the way, one key example on importance of masks is Japan. It's not testing, it's not socially-isolating, it's dense with public transportation. But people wear masks. It *will* have an outbreak but with *only* masks slowing things down, they haven't yet become NYC or Lombardy.

Yes! "We found virus bits in a PCR machine" is not the same as viable virus that can infect you—let alone a high viral load. In general, stainless steel-type high-touch surfaces are most dangerous, porous (cardboard, paper) is least. Wipe, don't panic. https://twitter.com/Charliewking/status/1247180858366349312