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Bacteria cause strep throat
Viruses cause most sore throats. However, strep throat is an infection in the throat and tonsils caused by bacteria called group A Streptococcus (group A strep).
How you get strep throat
Group A strep bacteria are very contagious. Generally, people spread the bacteria to others through
- Respiratory droplets
- Direct contact
Rarely, people can spread group A strep bacteria through food that is not handled properly (visit CDC’s food safety page).
It usually takes two to five days for someone exposed to group A strep bacteria to become ill with strep throat.
Group A strep bacteria often live in the nose and throat. People who are infected spread the bacteria by talking, coughing, or sneezing, which creates respiratory droplets that contain the bacteria.
People can get sick if they:
- Breathe in respiratory droplets that contain the bacteria
- Touch something with those droplets on it and then touch their mouth or nose
- Drink from the same glass or eat from the same plate as a person infected with group A strep bacteria
People can also spread group A strep bacteria from infected sores on their skin. Other people can get sick if they:
- Touch sores on the skin caused by group A strep bacteria (impetigo) or come into contact with fluid from the sores
Symptoms often include pain and fever
In general, strep throat is a mild infection, but it can be very painful.
Common symptoms may include:
- Pain when swallowing
- Sore throat that can start very quickly and may look red
- Red and swollen tonsils
- White patches or streaks of pus on the tonsils
- Tiny, red spots on the roof of the mouth, called petechiae (pronounced pi-TEE-kee-eye)
- Swollen lymph nodes in the front of the neck
A healthy throat
Signs of strep throat
Less common symptoms may include vomiting
Some people, especially children, may have other symptoms, too.
Other symptoms may include:
- Stomach pain
- Nausea or vomiting
- Rash (scarlet fever)
Symptoms do NOT include cough
The following symptoms suggest a virus is the cause of the illness instead of strep throat:
- Runny nose
- Hoarseness (changes in your voice that make it sound breathy, raspy, or strained)
- Pink eye (conjunctivitis)
Some people are at increased risk
Anyone can get strep throat, but there are some factors that can increase the risk of getting this common infection.
Strep throat is more common in children than adults. It is most common in children 5 through 15 years old. It is very rare in children younger than 3 years old.
Adults who are at increased risk for strep throat include:
- Parents of school-aged children
- Adults who are often in contact with children
Close contact with another person with strep throat is the most common risk factor for illness. For example, if someone has strep throat, the bacteria often spread to other people in their household.
Infectious illnesses tend to spread wherever large groups of people gather. Crowded settings can increase the risk of getting a group A strep infection. These settings include:
- Daycare centers
- Military training facilities
A simple test gives fast results
Your doctor may swab your throat to test for bacteria.
A doctor will determine what type of illness you have by asking about symptoms and doing a physical exam. If they think you might have strep throat, they will swab your throat to test for strep throat. There are two types of tests for strep throat: a rapid strep test and throat culture.
Rapid strep test
A rapid strep test involves swabbing the throat and running a test on the swab. The test quickly shows if group A strep bacteria are causing the illness.
- If the test is positive, doctors can prescribe antibiotics.
- If the test is negative, but a doctor still suspects strep throat, then the doctor can take a throat culture swab.
A throat culture takes time to see if group A strep bacteria grow from the swab. While it takes more time, a throat culture sometimes finds infections that the rapid strep test misses.
Culture is important to use in children and teens since they can get rheumatic fever from an untreated strep throat infection. For adults, it is usually not necessary to do a throat culture following a negative rapid strep test. Adults are generally not at risk of getting rheumatic fever following a strep throat infection.
Antibiotics are used for treatment
Doctors treat strep throat with antibiotics. Benefits of antibiotics include:
- Decreasing how long someone is sick
- Decreasing symptoms (feeling better)
- Preventing the bacteria from spreading to others
- Preventing serious complications like rheumatic fever
Someone with strep throat should start feeling better in just a day or two after starting antibiotics. Call the doctor if you or your child are not feeling better after taking antibiotics for 48 hours.
When to return to work or school
People with strep throat should stay home from work, school, or daycare until they:
- No longer have a fever
- Have taken antibiotics for at least 12 hours
Use antibiotics properly
- Take the prescription exactly as the doctor says to.
- Keep taking the medicine even if you or your child feels better. Don’t stop unless the doctor says to stop.
You can find more guidance on taking antibiotics on CDC’s Antibiotic Do’s & Don’ts Page.
Not everyone needs antibiotics
Someone who tests positive for strep throat but has no symptoms (called a “carrier”) usually does not need antibiotics. They are less likely to spread the bacteria to others and very unlikely to get complications.
If a carrier gets a sore throat illness caused by a virus, the rapid strep test can be positive. In these cases, it can be hard to know what is causing the sore throat.
If someone keeps getting a sore throat after taking the right antibiotics, they may be a strep carrier and have a viral throat infection. Talk to a doctor if you think you or your child may be a strep carrier.
Serious complications are not common
Complications can occur after a strep throat infection. This can happen if the bacteria spread to other parts of the body.
Complications can include:
- Abscesses (pockets of pus) around the tonsils or in the neck
- Swollen lymph nodes in the neck
- Sinus infections
- Ear infections
- Rheumatic fever (a disease that can affect the heart, joints, brain, and skin)
- Post-streptococcal glomerulonephritis (a kidney disease)
Protect yourself and others
People can get strep throat more than once. Having strep throat does not protect someone from getting it again in the future. While there is no vaccine to prevent strep throat, there are things people can do to protect themselves and others.
Wash your hands often to help prevent germs from spreading.
The best way to keep from getting or spreading group A strep is to wash your hands often. This is especially important after coughing or sneezing and before preparing foods or eating.
To prevent group A strep infections, you should:
- Cover your mouth and nose with a tissue when you cough or sneeze.
- Put your used tissue in the waste basket.
- Cough or sneeze into your upper sleeve or elbow, not your hands, if you don’t have a tissue.
- Wash your hands often with soap and water for at least 20 seconds.
- Use an alcohol-based hand rub if soap and water are not available.
You should also wash glasses, utensils, and plates after someone who is sick uses them. These items are safe for others to use once washed.
Antibiotics help prevent someone with strep throat from spreading the bacteria to others.
Information Source: CDC