Why of all developed countries the USA is the most at risk for a crazy pandemic?
Because of absurd US healthcare cost. 27 millions americans have absolutely no coverage. Yes under federal law a patient must be taken care of at emergency but still the hospital will send a huge crazy bill which will pend on that patient's profile forever. Therefore many more then this 27 millions will not seek treatment if they get sick. They cannot afford it.
What's worst is the law does not forbid employers to lay off a sick employee... What do you think happens? Employee will show to work even if sick. Risking to infect many other people.
If someone in the US cannot afford health insurance the government will provide it, it's called medicaid. The 27 million Americans you mention can have FREE healthcare if they cannot afford it. All they have to do is visit their state's website.
Regarding the laying off of sick employees, that's complete bullshit. If a person is unable to work for a health related issue they can get short term disability. If their ailment is longer than I believe 6 weeks they can get long term disability. Regardless, if any company simply laid off an employee for being sick they would get their balls sued off.
Lastly, employees showing up for work when they are sick is mostly because they feel that they have too much work to do or don't want to take a sick day.