Dr. Beth Zeeman says she can spot a case of influenza from 20 paces. It's not like a common cold.
"People think they've had the flu when they've had colds," Zeeman, an emergency room specialist at MetroWest Medical Center in Framingham, Mass., tells Shots. "People use the word 'flu' for everything. But having influenza is really a different thing. It hits you like a ton of bricks."
Joachim Santos, a carpenter from Brazil in a nearby examining room, says he's never been as sick in all his 57 years. "I worry that it's going to get more serious and I could die," he says.
The other day, Zeeman treated a strapping 20-year-old man who also thought he was going to die.
Dr. Andrew Pavia, an infectious disease specialist at the University of Utah, says flu has certain hallmarks. "A classic case of flu starts off suddenly with high fever, maybe shaking chills, severe muscle and body aches," he says. "It's not uncommon for people to say their hair hurts, they hurt so badly."
But not everybody who's getting sick this winter has the flu. Pavia says the nation's getting hit by a triple whammy of respiratory viruses right now.
One of them is called respiratory syncytial virus.
"There's a great deal of RSV circulating right now," Pavia says. "RSV causes pretty severe respiratory disease in children, particularly younger children under about 2. It's pretty common for them to be hospitalized with wheezing and shortness of breath."
And then there's the parainfluenza virus. Although it has "influenza" in its name, it's a different bug altogether.
"It most commonly causes croup that kind of barky cough that children get," Pavia says. "But in adults, it can cause laryngitis and a prolonged cough."
But good old flu or rather, three different strains now circulating across the nation is the first among equals when it comes to respiratory miseries.
"Flu reliably kills people every year," Pavia says. "It kills healthy people as well as the very young, the very old and debilitated people. So I still treat flu with the greatest degree of respect."
There's a fourth virus also making some Americans sick the nasty norovirus.
Some people call it "stomach flu," but it really doesn't have anything to do with the flu. Its specialty is intestinal, causing nonstop diarrhea and what doctors vividly call "projectile vomiting." That can quickly lead to a dangerous level of dehydration.
Norovirus is also notorious among medical people for being hard to get rid of.
"It requires cleaning, cleaning and cleaning again in order to remove norovirus from environmental surfaces," Pavia says.
By comparison, the influenza virus is a pushover, environmentally speaking.
"It doesn't survive very well in soft environments, like tissues," Pavia says. "But it can last up to 12 hours on hard surfaces like counters under ideal conditions."
That means you probably can pick up flu viruses from touching doorknobs or sink faucets, or using a keyboard that somebody with contaminated fingers just typed on.
But most likely, flu is passed on by shaking hands with somebody who's infected and may or may not be showing symptoms yet or by being coughed or sneezed on.
That's why public health people keep harping on coughing or sneezing into your sleeve to avoid spraying virus on people nearby. And washing your hands often, silently singing "Happy Birthday" to yourself twice through to make sure you're doing a good job.
Those things do work.
And if they don't, pay attention to the kind of symptoms you get when you get sick.
"If you're having chills that are so bad that your teeth are chattering and the chair is shaking under you, you're pretty sick," Pavia says. "And if it's not flu, it's probably a serious bacterial infection. And it's a pretty good indication you should see a doctor."
But in January 2013, Pavia says if you've got those symptoms, there's an 80 percent chance you've got the flu.