It's that time of year again. You wake up with a scratchy throat, stuffy nose, a little achy — maybe a fever. Is it a classic head cold, or do you need to be more concerned? Could it be the flu?

"There's lots of confusion out there, because both are viral respiratory illnesses," says Dr. Yul Ejnes, an internal medicine specialist in private practice in Rhode Island and spokesperson for the American College of Physicians. "No one likes to get a cold, but people are more fearful of the flu."

And rightly so.

Last year's influenza season was particularly severe, resulting in an unusually high number of hospitalizations and deaths from flu complications.

So, if you do have the flu, it's important to consult with your health care provider about treatment. And distinguishing between a cold and flu may be easier than you think, Ejnes says. There are some clear distinctions between the two similar types of viral illness in terms of symptoms — how quickly they appear and how severe they become.

Suddenly flattened? Think flu

Flu symptoms, Ejnes says, usually start abruptly — though you can spread the virus before symptoms surface.

"Patients can pretty much tell you when the symptoms hit them — after lunch, for example, or yesterday afternoon," says Ejnes.

A cold, on the other hand, takes a couple of days to build up. You may have a scratchy throat one day and then the nose starts to get stuffy the next day.

You may also develop a fever with a cold. But typically, it's a "low-grade" rise in temperature, hovering around 99 or 100 degrees Farenheit.

With flu, that fever is usually significantly higher — at least 101 degrees. Chills and body aches are another flu hallmark or, as Ejnes says, "feeling like a truck ran you over — where you can't even move a muscle."

Dragging yourself out of bed can seem impossible when you have the flu. "You're just wiped out with total body fatigue," he says, whereas with a cold, people often "soldier on" and get out of bed for work or social activities.

Heading to work isn't a good idea, of course, even with a mild cold, because it exposes others to the virus -- but lots of people do it. (Colds tend to be most contagious in the first several days of illness.)

There can be congestion and cough from the postnasal drip of a head cold, but it's not nearly as severe as with flu. Influenza can trigger long bouts of coughing and even trouble breathing.

So, when patients tell Ejnes that their symptoms developed suddenly, their fever is high and their body aches severe, he assumes flu, he says.

But should those symptoms send you to the doctor? That depends, Ejnes says. If you're a healthy adult without any chronic health problems, you may instead do fine with merely phoning your doctor, who can quickly prescribe any of several antiviral medications. That medicine is most effective when given within two days of symptoms.

"It's not a miracle drug by any stretch," cautions Ejnes, but it can offer some relief by reducing the severity of symptoms and the duration of the illness by a day or so.

Ejnes says he prefers a phone chat to a visit in such cases — partly to limit the number of people in his waiting room who have the flu.

"I've had the most ironic scenarios, where somebody's coming into the office to get a flu shot and — while they're waiting to be called in — they're sitting next to someone who's coming in with symptoms that might be the flu."

So call first.

'Red flags' that escalate risk

However, doctors do want people who are at high risk of developing complications to be seen by the health team when flu is suspected, says infectious disease physician Dr. Matthew Zahn. He's the medical director of the Division of Epidemiology and Assessment for the Orange County Health Care Agency, in Southern California, and spokesperson for the Infectious Disease Society of America.

This at-risk group includes children under age 5, whose immune systems are still developing; adults 65 and older, whose immune systems are waning; pregnant women; and individuals who have certain underlying medical conditions. These pre-existing conditions include asthma, chronic lung disease, heart disease, kidney disorders and liver disorders — all are known to diminish the strength of the immune system and the ability to fight off influenza.

Antiviral medicine can be helpful for this group, he says, even if it is given more than two days after flu symptoms appear.

And whether you get treatment or not, there are some important "red flags" to be aware of with the flu, says Zahn.

Watch for "any sort of breathing problems," he says. Coughing occasionally is one thing, but if you're having trouble catching your breath, go see your doctor "really quickly."

Breathing problems can be symptomatic of pneumonia, a common and serious complication of the flu, in which the air sacs of one or both lungs become clogged.

A sudden and significant change in mental health status with the respiratory symptoms is also a red flag, Zahn says. If you or a loved one have trouble focusing or are not as alert as normal, make your way to a doctor right away.

Flu shots aren't just for the kids and grandpa

While antiviral medication can reduce symptoms, infectious disease specialists agree that the best way to prevent the flu is to get the flu vaccine.

"Each year we have tens of thousands of people die of flu," Zahn says, and the vaccine can help prevent that. While flu seasons are unpredictable and strains of the virus mutate from year to year, vaccines can still be anywhere from 40 percent to 60 percent effective in preventing severe complications and hospitalization.

Vaccination rates against flu are highest among Americans 65 and older and among children 4 and younger, he says, but most others could benefit from a flu shot, too. And that's not happening — among American adults aged 18 to 64, typically less than half get immunized.

Of course, it's best to get your flu vaccine at the beginning of flu season — in the fall — but it's not too late. The influenza season runs throughout winter.

As for treating a cold, well, you're pretty much out of luck.

"The reality is nothing is available to shorten the duration of a head cold," says internist Ejnes.

Over-the-counter medication can ease symptoms, he says. Decongestants can help reduce cough, nasal sprays can help reduce stuffiness, and lozenges can help relieve a sore throat.

"Some folks have more luck with these OTC remedies than others," Ejnes says.

Then there is the ever-popular chicken soup, which can help you feel better — especially if there's lots of steam, which can help clear up nasal congestion.

But, bottom line, Ejnes says patients just have to do whatever they can to ease symptoms until the cold runs its course — usually in seven to 10 days. "There's nothing we can do to speed that process up."

Copyright NPR 2019.