Strep throat is caused by a specific type of bacteria called group A Streptococcus (Streptococcus pyogenes). It is a common and highly contagious infection that affects the throat and tonsils. The bacteria spread through respiratory droplets when an infected person coughs, sneezes, or talks, and you can also catch it by touching a surface with those droplets and then touching your mouth, nose, or eyes.
What Is Strep Throat Caused By?
Group A Streptococcus is the only cause of strep throat. This is a key distinction because many people use the term “strep throat” to describe any sore throat, but most sore throats come from viruses. Viral infections cause about 80 to 90 percent of sore throats in adults and a smaller but still significant percentage in children. Only the group A Streptococcus bacteria produces true strep throat.
The bacteria are spread through close contact. When someone who is infected coughs or sneezes, tiny droplets carrying the bacteria enter the air. If you breathe those in, or touch a contaminated surface and then touch your face, the bacteria can enter your body. The bacteria then attach to the tissues of your throat and tonsils, where they multiply and trigger inflammation.
How Do I Know It Is Strep and Not a Virus?
You cannot tell the difference by how you feel alone. A viral sore throat and strep throat share many symptoms, including pain, redness, and difficulty swallowing. However, strep throat has some distinguishing features that make it more likely.
Strep throat typically comes on suddenly, often with a severe sore throat and pain when swallowing. It frequently includes a fever above 101°F (38.3°C), swollen lymph nodes in the neck, and white patches or streaks of pus on the tonsils. The back of the throat may look red and swollen. Some people also develop tiny red spots on the roof of the mouth.
Viral sore throats, in contrast, usually develop gradually. They are often accompanied by a cough, runny nose, hoarseness, or conjunctivitis (pink eye). The presence of a cough, runny nose, or hoarseness makes strep throat much less likely.
No one should rely on symptoms alone for a diagnosis. A rapid antigen test or a throat culture performed by a healthcare provider is the only reliable way to confirm strep throat.
Who Gets Strep Throat Most Often?
Strep throat is most common in children between the ages of 5 and 15. It is rare in children under 3 years old. Adults can get it too, especially parents of school-aged children, teachers, or anyone who spends time in crowded indoor settings.
Certain environments increase the risk of transmission. Schools, daycare centers, and military barracks are common settings where the bacteria spread quickly. The infection is more prevalent in late winter and early spring, though it can occur at any time of year.
Close contact is the main risk factor. Living in the same household as someone with strep throat raises your risk significantly. Sharing food, drinks, or utensils with an infected person also spreads the bacteria.
What Complications Can Strep Throat Cause?
Most cases of strep throat resolve without serious problems, especially when treated promptly with antibiotics. However, untreated or severe infections can lead to complications. These are uncommon but serious enough that they explain why medical evaluation matters.
One local complication is a peritonsillar abscess, a collection of pus behind the tonsils. This causes severe throat pain, difficulty opening the mouth fully, muffled voice, and sometimes difficulty breathing. It requires drainage and intravenous antibiotics.
Rare but serious systemic complications can occur weeks after the initial infection. Acute rheumatic fever can damage the heart valves permanently. Post-streptococcal glomerulonephritis is a kidney condition that can develop after a strep infection. Both are triggered by the body’s immune response to the bacteria, not by the bacteria directly.
These complications are why doctors take strep throat seriously. Treating the infection with antibiotics within the first 9 days of symptoms significantly reduces the risk of rheumatic fever. Antibiotics do not prevent post-streptococcal glomerulonephritis, but prompt treatment is still the standard of care.
How Is Strep Throat Treated?
Strep throat is treated with antibiotics. Penicillin and amoxicillin are the first-line choices for most people. For those allergic to penicillin, cephalexin, clindamycin, or azithromycin are common alternatives. The choice depends on the specific allergy and the person’s medical history.
Antibiotics serve two purposes. They shorten the duration of illness by about one to two days, and they prevent serious complications like rheumatic fever. They also reduce the period of contagiousness. People on antibiotics are typically no longer contagious after 24 hours of treatment and no longer have a fever.
Without antibiotics, a person with strep throat remains contagious for about two to three weeks. With antibiotics, the contagious period drops to roughly 24 hours after the first dose. This is a major reason why testing and treatment matter for public health, not just personal comfort.
Pain relief is also important. Over-the-counter medications like ibuprofen or acetaminophen reduce fever and throat pain. Warm salt water gargles, cold liquids, and throat lozenges can provide additional comfort, though they do not treat the infection itself.
When Should I See a Doctor?
You should see a healthcare provider if you have a sore throat that lasts more than two days, a fever above 101°F, difficulty swallowing, or swollen glands in your neck. You should seek urgent care if you have difficulty breathing, drooling, or severe difficulty opening your mouth. These can be signs of a peritonsillar abscess or airway obstruction.
You should also see a doctor if you have been in close contact with someone diagnosed with strep throat and develop symptoms. Testing is quick and usually involves a swab of the back of the throat. The rapid test gives results in minutes, though it can occasionally miss the infection. If the rapid test is negative but symptoms strongly suggest strep, a throat culture may be sent to a lab, with results in 24 to 48 hours.
Not every sore throat requires a doctor visit. Viral sore throats are self-limiting and resolve on their own. But because strep throat requires antibiotics and carries the risk of complications, it is better to be tested when symptoms are suggestive.
How Can I Prevent Spreading Strep Throat?
Good hygiene is the most effective prevention. Wash your hands frequently with soap and water for at least 20 seconds, especially after coughing or sneezing. Use alcohol-based hand sanitizer when soap is not available. Do not share food, drinks, utensils, or personal items like toothbrushes.
Cover your mouth and nose with a tissue or your elbow when you cough or sneeze. Dispose of used tissues immediately. Avoid touching your face, especially your eyes, nose, and mouth.
If you have strep throat, stay home from work, school, or daycare until you have been on antibiotics for at least 24 hours and your fever has resolved without the use of fever-reducing medication. This is the standard public health recommendation to prevent further spread.
Frequently Asked Questions
Can strep throat go away without antibiotics?
Yes, strep throat can resolve on its own, but untreated infection carries a risk of rheumatic fever and other complications. Antibiotics are recommended because they shorten illness and prevent these serious outcomes.
Is strep throat contagious?
Yes, strep throat is highly contagious. You can spread it through respiratory droplets or by touching contaminated surfaces, and you remain contagious until you have been on antibiotics for 24 hours.
Can adults get strep throat?
Yes, adults can get strep throat, though it is most common in children aged 5 to 15. Adults who live with or care for children are at higher risk.
How long does strep throat last?
With antibiotics, symptoms usually improve within 24 to 48 hours, and most people feel better within a week. Without treatment, symptoms may last longer and complications become possible.
