How to Tell If You Have the Flu, Coronavirus, or Something Else
By: Robert Roy Britt
Tags: Health, Cold, Body, Coronavirus, Flu

How to Tell If You Have the Flu, Coronavirus, or Something Else

This symptom chart will help you determine which virus ails you

Photo: Guido Mieth/DigitalVision/Getty Images

Editor’s Note: This article is no longer updated and much has been learned about Covid-19 symptoms. For the latest on the disease, visit Elemental’s ongoing coverage of the coronavirus outbreak here.

The first sign of a scratchy throat is scientifically known to be accompanied by an “uh-oh” sensation, followed by the ironic hope that it’s “just a cold,” because otherwise it could be the onset of a disabling flu, the looming coronavirus, or some other infectious disease affecting the upper airways.

“Because colds and flu share many symptoms, it can be difficult (or even impossible) to tell the difference between them based on symptoms alone,” according to the U.S. Centers for Disease Control and Prevention. But in fact, the CDC’s own lists of symptoms for the two diseases draw notable distinctions in typical cases.

Symptoms of the new coronavirus, Covid-19, can indeed be difficult to distinguish from flu symptoms, but in recent weeks, infectious-disease experts have gotten a clearer picture of telltale signs, particularly fever early on, and which symptoms are rare in most cases but may show up when it becomes most serious.

There are distinct differences in the most likely symptoms of various viral infections and how fast they come on.

So, how do you know whether to call a doctor immediately or just settle in with a good book and some chicken soup?

There are distinct differences in the most likely symptoms of various virus infections and how fast they come on. This chart — and the deeper explanations below on four viruses getting a lot of attention these days — can’t replace a doctor’s diagnosis, but they may help you contemplate what you’re in for. If you have questions or concerns, consult a health care professional, and don’t let an unknown disease fester.

Common cold

Colds are caused by more than 200 different viruses, including strains of coronavirus and, more commonly, rhinoviruses. While miserable and exceedingly common, a cold is rarely as debilitating as the flu.

Frequency

Each year, a typical adult will catch two or three colds. Young children can get six or more annually.

Common symptoms

A gradual progression often starting with a sore throat, leading to sneezing, runny nose, stuffiness, and the annoying postnasal drip (that’s mucus running down your throat, attempting to wash the infection away).

Possible complications

Colds are much less likely to cause serious complications compared to the flu, but they can lead to ear infections, sinus infections, or, more rarely, bronchitis, pneumonia, or other secondary infections — all of which need medical treatment. Colds can also trigger or exacerbate asthma.

How it spreads

Through the air from a cough or sneeze, from the hands of an infected person, from hard surfaces, and via close contact with an infected person.

Contagious period

One to two days before symptoms appear and then until all symptoms are gone, as much as two weeks from the onset.

Influenza

Despite understandable fears of outbreaks like coronavirus, various strains of the flu — there are 29 different subtypes — cause far more deaths every year than most other viral outbreaks do across several years.

Frequency

About 8% of the U.S. population comes down with a flu bug every year. On average, it kills 12,000 to 61,000 Americans annually.

Common symptoms

Quick onset of fever over 100.4 degrees Fahrenheit, aching muscles, and chills are the characteristic signs.

Possible complications

Ear and sinus infections, pneumonia, worsening of chronic medical conditions, and death. As with other viruses, the flu tends to be most problematic for the young, the old, and anyone with a compromised immune system.

How it spreads

Through the air from a cough or sneeze, from the hands of an infected person, from hard surfaces, and via close contact with an infected person.

Cold and flu viruses can survive for 15 to 20 minutes on the skin and several hours on hard surfaces.

Contagious period

One day before symptoms start, and then for three to seven more days.

Norovirus

This fast-acting germ, often incorrectly called “stomach flu,” inflames the stomach or intestines and leads to intense but typically short-lived gastrointestinal discomfort. It’s the leading cause of outbreaks of food poisoning in the United States (more common than bacterial outbreaks from salmonella or E. coli).

Frequency

About 20 million Americans, or 6% of the population, suffer an acute case of norovirus-induced gastroenteritis each year.

Common symptoms

Unlike cold or flu viruses, norovirus brings on sudden, often severe and frequent vomiting and/or diarrhea.

Possible complications

Dangerous dehydration. Some 400,000 U.S. norovirus cases annually lead to emergency room visits, with children predominating. Between 570 and 800 patients die—mostly kids, older people, and people with compromised immune systems.

How it spreads

Most notoriously through human poop and vomit (including airborne puke droplets). A droplet of diarrhea the size of a pinhead can contain enough norovirus particles to make someone else sick. The disease is often transmitted by food harvested in contaminated water, or it’s passed along at a restaurant or at home by an infected person preparing food served raw or touching food after it’s cooked.

Contagious period

Before symptoms start and up to two weeks after recovery.

Covid-19 coronavirus

Symptoms of Covid-19 caused by the coronavirus, are difficult to distinguish from influenza, health experts say, and can range from mild and even almost unnoticed for some people to severe and deadly for others. (Scientists can’t yet explain why, but such varied reactions also occur with other viral diseases.)

Frequency

That remains to be determined through the lens of history, but cases are mounting in the U.S. and around the globe. [See the latest updates in Elemental’s ongoing coverage of the coronavirus here.]

Most common symptoms

Fever, cough, and shortness of breath. Fever early on is a distinguishing symptom. Dry coughs follow in cases that become moderate or severe. Shortness of breath is a telltale and dangerous development distinguishing COVID-19 from influenza or a cold.

But other people, including some children, have been diagnosed with the disease only after mild cold- or flu-like symptoms. Still others are infected and infectious while showing no symptoms.

And recently, doctors say a significant number of people with COVID-19 have lost their sense of smell, though it hasn’t been studied yet to determine for sure if this is a symptom of COVID-19 or related to some other condition.

Possible severe complications

Pneumonia, severe acute respiratory syndrome, kidney failure, death.

How it spreads

Through the air from a cough or sneeze, from hard surfaces, and via close contact with an infected person (within six feet, the CDC says). Also, possibly in human feces, according to a study published February 17 in the journal Emerging Microbes and Infections, plus one other previous study and another one announced since. Researchers have said that the spread through poop and the potential for the disease to cause diarrhea could be a rapid transmission factor, but most evidence suggests this is not a primary means.

Contagious period

Possibly before symptoms start, but mostly when symptoms are present. (The specifics are not yet known to science.)

Emerging view of coronavirus symptoms

Because the Covid-19 coronavirus emerged only in December, the CDC has yet to firmly state the likelihood of the various symptoms beyond the three most common. “We do not have any more specifics at this time, because there has been a range of possible symptoms for people with Covid-19,” CDC spokesperson Richard Quartarone tells Elemental.

However, researchers recently studied 138 people with advanced cases of the virus who had been hospitalized with pneumonia after being infected with Covid-19 in Wuhan, China. The research, published February 7 in JAMA, revealed preliminary data showing the percentage of patients with these symptoms:

Fever: 98.6%

Fatigue: 69.6%

Cough: 59.4%

Aches: 34.8%

Difficulty breathing: 31.2%

Nausea: 10.1%

Diarrhea: 10.1%

Headache: 6.5%

Vomiting: 3.6%

But these were patients with severe symptoms, and nearly half of them had preexisting medical conditions, including hypertension, diabetes, and heart disease, so the figures may not represent how the disease typically manifests in healthy individuals.

In other research recently published by the Chinese Center for Disease Control and Prevention, 81% of 44,672 coronavirus cases were mild, including some in which symptoms were like a minor flu and others that were like a minor cold. The fatality rate for COVID-19 is not known for sure, but data from cases in Italy, published on March 17 by the Journal of the American Medical Association, finds death rates ranging from 0.3% in people age 30–90 to 3.5% in the 60–69 set and 19.7% and higher for people 80 and older. (Seasonal flu typically kills about 0.1% of all people infected.)

Serious symptoms

A big caveat to all symptom spotting: No given disease presents the same in each person or each case, and there are many different strains of cold, flu, and norovirus with different degrees of impact. Sometimes fever does not accompany influenza, for example. Symptoms that are rare can occur. Children, the elderly, and anyone with existing health issues may experience more severe symptoms than others. Among the list of a dozen serious symptoms that should trigger immediate medical attention:

Seizures

Chest pains

Trouble breathing or fast breathing

Fever lasting more than four days or rising above 104 degree Fahrenheit

Conditions that lasts beyond typical duration

Conditions that improve then worsen

Severe dehydration

Bluish lips or face

And there are, of course, many other diseases that may seem cold- or flu-like at the outset but require prompt medical attention. Among them:

Measles may start out with mostly cold-like symptoms but is accompanied by a rash and tends to spike a fever to 104 degrees Fahrenheit.

Mumps starts out flu-like but typically swells the salivary glands, causing puffy cheeks and a swollen jaw.

Strep throat tends to start quickly with a sore throat and painful swallowing. (Strep is a bacterial infection, not a virus, that can be treated effectively with antibiotics, which don’t work on viruses.)

Seasonal allergies can also mimic cold and flu symptoms. But they’re often marked by itchy, watery eyes, which are not common to colds, the flu, or other infectious diseases. Allergies do not trigger headaches or muscle aches. And, of course, allergies can last weeks.

Spread the word, not the virus

Viruses have evolved over millions of years to be supremely capable of surviving outside a host and infecting another — to go viral — simply by floating through the air inside the mucus of a cough or sneeze. Even talking can unleash virus-containing droplets seeking a new host. “These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs,” the CDC says.

Viruses can also spread when an infected person touches their face and then shakes a hand, turns a doorknob, or prepares food. Cold and flu viruses can survive for 15 to 20 minutes on the skin and several hours on hard surfaces. New research on Covid-19 suggests this coronavirus might survive for a few days on surfaces.

If you think you’re getting sick, or if you have a fever or are coughing, sneezing or vomiting:

If you feel desperately ill, have any of the serious signs mentioned above, or suspect coronavirus because you visited an area with an outbreak or have been around someone diagnosed with the disease, put down that great book, forget the chicken soup, and call your doctor immediately or get to an emergency room.

This article has been updated on 3/19.

The coronavirus outbreak is rapidly evolving. To stay informed, check the U.S. Centers for Disease Control and Prevention as well as your local health department for updates. If you’re feeling emotionally overwhelmed, reach out to the Crisis Text Line.