Strep throat is a bacterial infection. It’s caused by group A Streptococcus bacteria, so there’s no such thing as “viral strep.” Most sore throats, though, are caused by viruses, which is why a quick test is the only way to know whether a sore throat is strep.
Get care right away if you or your child has trouble breathing, can’t swallow, is drooling, or makes a high-pitched sound when breathing. The NHS treats these as emergency signs: call 911 or go to the emergency room. familydoctor.org from the American Academy of Family Physicians (AAFP) adds severe neck swelling and a muffled “hot potato” voice.
In the video above, family physician Dr. Richard Honaker explains that there are two kinds of sore throats, viral and bacterial, and that strep is the bacterial kind that needs antibiotics. His rule of thumb: a virus usually brings a runny nose and a cough along with the sore throat, and strep usually doesn’t. For a full overview of strep symptoms and treatment, see Strep Throat vs. Viral Sore Throat: How to Tell the Difference. This article focuses on the viral-or-bacterial question.
Is strep a virus?
No. Strep throat is a throat and tonsil infection caused by group A Streptococcus bacteria (the species is Streptococcus pyogenes), according to Cleveland Clinic. A virus can never cause strep throat.
The confusion makes sense. Cleveland Clinic says viruses, not bacteria, cause most sore throats, and the two can look alike. A sore throat caused by a virus is usually called a viral sore throat or viral pharyngitis (“pharyngitis” just means an inflamed throat). When people search for “viral strep throat,” they usually mean one of these.
| Strep throat | Viral sore throat | |
|---|---|---|
| Germ | Group A Streptococcus bacteria | Viruses, often the ones behind colds and flu |
| How common | The less common cause | The most common cause |
| Cough, runny nose, hoarse voice, pink eye | Usually not | Common |
| Test | Rapid strep test or throat culture | Usually none |
| Antibiotics | Yes, if a test confirms strep | No; antibiotics don’t work on viruses |
The table is a guide, not a diagnosis. Symptoms overlap, and only a test can confirm strep.
How do you tell if a sore throat is viral or bacterial?
You can’t be sure by looking. Cleveland Clinic and Merck Manuals both say strep and viral sore throats can look the same, so a test is needed. But some signs make one more likely.
Signs that point to a virus. familydoctor.org and the American Academy of Pediatrics (AAP) list a cough, runny nose, hoarseness and pink eye. Cleveland Clinic adds mouth sores. familydoctor.org says testing isn’t needed when clear viral symptoms are present.
Signs that point to strep. Merck Manuals says doctors suspect strep based on four findings:
- fever
- swollen, tender lymph nodes (glands) in the neck
- pus on the tonsils
- no cough
Other common strep signs, according to Cleveland Clinic and familydoctor.org, include a sore throat that starts suddenly, pain when swallowing, red and swollen tonsils that may have white patches, and tiny red spots on the roof of the mouth. Children may also have a headache, stomach pain, nausea or vomiting. A sandpaper-like rash can be a sign of scarlet fever, which is caused by the same bacteria.
Age matters too. Strep is most common in children ages 5 to 15 and rare in children under 3, Cleveland Clinic says. The AAP notes that viruses are the most common cause of sore throats in babies, toddlers and preschoolers.
Can you have strep throat without a fever?
It’s possible. Fever is one of the most common strep symptoms, and Merck Manuals lists it among the main findings doctors look for. But fever isn’t required:
- MedlinePlus says strep symptoms can be mild or severe.
- MedlinePlus also notes that some people carry strep bacteria in their throat without being sick.
- The flip side is true too: viral sore throats can cause a fever, according to Cleveland Clinic.
So a fever, or the lack of one, can’t rule strep in or out. If the other signs point to strep, a test is the way to know.
Rapid strep test vs. throat culture
Both tests start the same way: a swab of the back of the throat and the tonsils.
| Rapid strep test | Throat culture | |
|---|---|---|
| Results | Within minutes, during the visit | Takes longer; MedlinePlus says 1 to 2 days |
| Accuracy | A positive result confirms strep, but the test can miss it (Merck Manuals, MedlinePlus) | Cleveland Clinic calls it the “gold standard”; it can find strep a rapid test missed |
| When it’s used | First test for most people | Often after a negative rapid test in a child or teen |
Cleveland Clinic and familydoctor.org say children and teens with a negative rapid test should have a throat culture, while adults usually don’t need one. Merck Manuals explains why: strep and rheumatic fever are much less likely in adults.
A negative test generally means the sore throat is viral, so antibiotics aren’t needed, the AAP says.
How is strep treated, and how is a viral sore throat treated?
Strep throat is treated with antibiotics once a test confirms it. Penicillin or amoxicillin is usually the first choice, according to MedlinePlus and Cleveland Clinic. If you’re allergic to penicillin, your doctor will pick another antibiotic. Antibiotics help you feel better sooner, make you contagious for less time, and lower the risk of complications such as rheumatic fever. Take the medicine exactly as prescribed and finish it, even after you feel better.
A viral sore throat doesn’t get better with antibiotics. The NHS says sore throats usually get better on their own within a week, and Cleveland Clinic says most sore throat symptoms go away within three to 10 days.
For comfort with either kind, Cleveland Clinic, MedlinePlus and the NHS suggest:
- warm or cold fluids, and cool or soft foods
- gargling with warm salt water (not for young children)
- lozenges, hard candy or ice chips for older children and adults (young children can choke on them)
- a cool-mist humidifier
- an over-the-counter pain reliever, after asking your doctor or pharmacist which one is right for you, and following the label
Don’t give aspirin to children or teens, because of the risk of Reye syndrome (familydoctor.org, Cleveland Clinic).
How long is strep throat contagious?
Strep spreads through droplets from coughs, sneezes and talking, and through shared cups and utensils.
- Without treatment: Cleveland Clinic says strep throat can be contagious for weeks if it isn’t treated.
- With antibiotics: Cleveland Clinic says that about 12 to 24 hours after starting the right antibiotic, you’re much less likely to spread it. MedlinePlus says most people can spread strep until they’ve taken antibiotics for 24 to 48 hours.
- Back to school or work: familydoctor.org says to stay home until the fever is gone and you’ve had at least 12 to 24 hours of antibiotics. MedlinePlus says to stay home until you’ve taken antibiotics for at least a day.
MedlinePlus also suggests replacing your toothbrush after 2 or 3 days on antibiotics, before you finish the medicine, so you don’t reinfect yourself.
When to see a doctor
See a doctor for:
- a sore throat with a fever but no cough or runny nose
- swollen, tender glands in the neck, or white patches on the tonsils
- a rash with a sore throat
- a sore throat that doesn’t improve after a week (NHS), or that keeps coming back
- strep that isn’t better after 48 hours on antibiotics (Cleveland Clinic, familydoctor.org)
- signs of dehydration, such as peeing less than usual or dark, strong-smelling pee (NHS)
- a weakened immune system (NHS)
Go to the ER or call 911 for the emergency signs at the top of this article.
Frequently asked questions
Is strep throat a viral infection?
No. Strep throat is always bacterial. It’s caused by group A Streptococcus. A sore throat caused by a virus is a viral sore throat, not strep, even if it looks similar.
Is there such a thing as viral strep throat?
No. “Strep” refers to Streptococcus bacteria, so strep can’t be viral. Viruses do cause most sore throats, and some of them cause red, swollen tonsils with white patches, Cleveland Clinic says. That’s why a strep test matters.
What’s the difference between a sore throat and strep throat?
Strep throat is one specific cause of a sore throat: a bacterial infection that needs antibiotics. Most other sore throats come from viruses, often a cold or flu, and get better on their own. Viral sore throats tend to come with a cough, runny nose or hoarse voice.
How long does a viral sore throat last?
The NHS says sore throats usually get better on their own within a week. The AAP says viral sore throats in children usually go away within 7 to 10 days. See a doctor if it lasts longer or gets worse.
Can a viral sore throat turn into strep?
The sources we read don’t say that one turns into the other. They’re caused by different germs. If a sore throat gets worse instead of better, or new signs of strep appear, see a doctor for a test.
Do I need antibiotics for a sore throat?
Only if a test shows strep or another bacterial infection. The NHS says antibiotics usually don’t relieve symptoms or speed recovery for a sore throat that isn’t bacterial. For more on when antibiotics help and when they don’t, see Antibiotics for an Upper Respiratory Infection.
More on sore throats in children: Is Your Child’s Sore Throat Caused by a Virus or Strep? Wondering if it’s allergies instead? See Allergy Symptoms vs. a Cold.
Find a doctor: Dr. Richard Honaker (family medicine), Dr. Bradley Friedman (family medicine) and Dr. Timothy Ragsdale (ear, nose and throat), all in Dallas-Fort Worth.
Sources
- Cleveland Clinic. Strep Throat.
- Cleveland Clinic. Sore Throat (Pharyngitis).
- Cleveland Clinic. Upper Respiratory Infection (URI).
- American Academy of Family Physicians, familydoctor.org. Strep Throat.
- American Academy of Pediatrics, HealthyChildren.org. Strep Throat, Sore Throat or Tonsillitis: What’s the Difference?.
- Merck Manual Consumer Version. Streptococcal Infections.
- MedlinePlus (U.S. National Library of Medicine). Strep throat.
- NHS. Sore throat.
This article is for general information only and is not medical advice. Talk with a qualified health professional about your own situation. If you think you may have a medical emergency, call 911.
