For the first time in 13 years, the Center for Disease Control (CDC) has announced that every part of the U.S. is experiencing widespread flu activity. The CDC keeps track of the progression on a map -- and the map is currently almost all the same color.

 The 2018 strain of flu is an “H3” strain and those are usually the worst. (The 2018 variety is officially named H3N2.)

The term “epidemic” is being applied and that is disturbing, but the CDC explains that typically each year, the flu reaches “epidemic” status.” What’s different about this year is that the strain is exceptionally severe and is hitting young children and older adults hardest.

What can you do? Standard advice is to wash your hands frequently, especially after touching surfaces that other people have touched: shopping carts, stair rails, door handles, chair backs, money, etc. If you're out to eat, be wary of menus, which are covered in germs. Washing hands is best, but sometimes it's not possible, so carry a small bottle of hand sanitizer with you to use when in a bind. Germs can stay active on hard surfaces for 24 hours.

Experts are recommending you still get a flu shot if you haven’t already, even though it may only be effective with 30% of the flu bugs circulating this year. The high-dose flu shot recommended for people 65 and older contains four times as much flu virus antigen — the part of the vaccine that stimulates the immune system — as standard flu vaccines. The reason for this recommendation is that as people get older, the amount of antibodies they produce begins to decline and the higher-dose vaccine compensates.

Of course, what you’d like to do is avoid being in crowded places with a lot of other people, some of whom may already be ill. Experts talk about an “infection zone” which can extend all around you up to 6 feet. So standing in lines, sitting in auditoriums, or working in an office expose you to more germs.

Of course, staying home until the epidemic is over (it could last until early April) isn’t realistic.

For example, what if you need to fly? A report on ABC News offered this specific advice. Don’t be embarrassed to wipe down that tray in front of you with a disinfectant cloth. Most airlines don’t clean those tray tables between flights. The other advice is to choose a window seat, where fewer people are likely to walk by or touch your seatback to steady themselves., and turn up the air circulation above you.

Whether you’re flying or carrying on with your regular routine, be sure not to get dehydrated. Once the mucous membranes in your nose and mouth get dry, you lose a valuable defense system for preventing respiratory viruses.