AZUZ: And a flu strain circulating in the U.S. this year, like the one that hit Australia last year, is a nasty one. Widespread flu activities are being reported in every part of the continental U.S. at the same time. This is the first year that's happened in the 13 years that the Centers of Disease Control has been monitoring the flu.
One reason: these year's vaccine doesn't appear to be very effective against the actual flu virus that's spreading.
Experts predict it will be about 30 percent effective. In recent years, the vaccine has been 40 and 50 percent effective, though there was an exception in the 2014 to 2015 season when the vaccine was only 19 percent effective, according to the CDC. And "The New York Times" reports that this season is looking a lot like that one.
The hopeful news is that experts think the flu season maybe hitting its worst point and that it's starting to level off. But it takes weeks for flu activity t actually slow down.
DR. SANJAY GUPTA, CNN CHIEF MEDICAL CORRESPONDENT: Let me try and settle this flu shot thing, although I'm sure it's going to keep coming up again and again.
SUBTITLE: Debunking flu myths.
GUPTA: You can't get the flu from the flu shot. It's a dead virus, it can't actually cause flu.
Why do people feel sort of crummy afterward? It's because the flu vaccine is actually working, making your immune system fire up, get ready and recognize it, if it actually sees the flu, how to kill it.
No, it's not 100 percent fail safe. But it's still going to offer a lot of protection, so you are not going to be as sick as likely to get sick or if you do get sick, have a shorter duration.
OK, so if you are like me, your mom probably said, don't go outside in the cold without your hat on, you are going to catch the flu. You can't catch the flu from just simply being outside in the cold.
But it does raise the question, why are there so many more flu cases in the winter months? You are likely to stay indoors more. So, if one person is sick, more people are likely to get sick.
The sun is lower in the sky, and as a result, you have less Vitamin D actually being produced in your body. Your immune system starts to get suppressed a little bit. You are more likely to get sick with the flu.
The winter months tend to be lower humidity. Viruses like the flu virus they like lower humidity. They are likely to live longer.
So, your mom may have been right — I mean, look, moms are always right, but maybe not for the reasons you originally thought.