What is strep throat?
What causes strep throat?
Strep throat is caused by streptococcal (strep) bacteria. There are many different types of strep bacteria. Some cause more serious illness than others.
Although some people are quick to think that any painful sore throat is strep, sore throats are usually caused by a viral infection and not strep bacteria. A sore throat caused by a virus can be just as painful as strep throat. But if you have cold symptoms such as coughing, sneezing, or a runny or stuffy nose, you probably do not have strep throat.
What are the symptoms?
The most common symptoms of strep throat are:
- A sudden, severe sore throat.
- Pain when you swallow.
- Fever over 38.3°C (101°F).
- Swollen tonsils and lymph nodes.
- White or yellow spots on the back of a bright red throat.
You may also have a headache and belly pain. Less common symptoms are a red skin rash, vomiting, not feeling hungry, and body aches.
Strep throat can be passed from person to person. When a person who has strep throat breathes, coughs, or sneezes, tiny droplets with the strep bacteria go into the air. These droplets can be breathed in by other people. If you come into contact with strep, it will take 2 to 5 days before you start to have symptoms.
How is strep throat diagnosed?
Your doctor will do a physical examination, ask you about your symptoms and past health, and do a lab test such as a throat culture or rapid strep test.
To do a throat culture, the doctor will swab a sample of cells from the back of your throat. The sample will go into a special cup (culture) where the strep bacteria can grow over time. If strep bacteria grow, the doctor knows that you have strep. If the doctor does a rapid test and the test says that you don't have strep (the test is negative) but your symptoms suggest that you do, your doctor may want to do a throat culture to be sure. This is because rapid strep tests are not always accurate.
If the rapid strep test is positive and says that you do have strep, there's no need to do the throat culture.
How is it treated?
Doctors usually treat strep throat with antibiotics. Antibiotics shorten the time you are able to spread the disease to others (are contagious) and lower the risk of spreading the infection to other parts of your body. Antibiotics also may help you feel better faster.
You are contagious while you still have symptoms. Most people stop being contagious 24 hours after they start antibiotics. If you don't take antibiotics, you may be contagious for 2 to 3 weeks, even if your symptoms go away.
Your doctor may also advise you to take an over-the-counter medicine like acetaminophen (such as Tylenol) or ibuprofen (such as Advil or Motrin) to help with pain and lower your fever. Acetaminophen and ibuprofen are different products with different dosing recommendations. Talk to your child's doctor before switching back and forth between doses of acetaminophen and ibuprofen. When you switch between two medicines, there is a chance your child will get too much medicine. Studies have not shown any added benefit from alternating these medicines. Be safe with medicines. Read and follow all instructions on the label. Do not give aspirin to anyone younger than 18. It has been linked to Reye syndrome, a serious illness.
How do you prevent strep throat?
To avoid getting strep throat, it is a good idea to avoid contact with anyone who has a strep infection. If you are around someone who has strep, wash your hands often. Don't drink from the same glass or use the same eating utensils. And don't share toothbrushes.
Bacteria can live for a short time on doorknobs, water faucets, and other objects. It's a good idea to wash your hands regularly.
If you have a strep infection, there are things you can do to avoid spreading it to others. Use tissues you can throw away instead of handkerchiefs, wash your hands often, and do not sneeze or cough on others. Antibiotics can shorten the time that you are contagious. It is a good idea to stay home from work or school until 24 hours after you have started antibiotics.
Frequently Asked Questions
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Strep throat is caused by streptococcal (strep) bacteria, most often by group A beta-hemolytic streptococcus (GABS). Other types of strep that can sometimes infect the throat are groups C and G strep bacteria.
Sore throats are most commonly caused by viral infections or other irritants such as smoke, allergies, dry air, or a throat injury, and not by a strep infection.
How the strep infection is spread
Strep throat can be passed from person to person. When a person infected with strep throat breathes, coughs, or sneezes, tiny droplets containing the strep bacteria are released into the air and are breathed in by other people.
Common symptoms of strep throat in children and adults include:
- Severe and sudden sore throat without coughing, sneezing, or other cold symptoms.
- Pain or difficulty with swallowing.
- Fever over 38.3°C (101°F). Lower fevers may point to a viral infection and not strep.
- Swollen lymph nodes in the neck.
- White or yellow spots or coating on the throat and tonsils.
- Bright red throat or dark red spots on the roof of the mouth at the back near the throat.
- Swollen tonsils, although this symptom may also be caused by a viral infection.
It is easy to tell when you have a sore throat or a cold. It is harder to know when you have strep throat. Typically, sore throats are caused by a viral infection and not strep bacteria. Strep throat usually does not occur with cold symptoms such as coughing, sneezing, or a runny or stuffy nose. The more cold symptoms you have, the less likely it is that your sore throat is a strep infection.
In some cases of strep infection, a skin rash develops and spreads over the neck and chest and eventually over the whole body. The rash feels rough like sandpaper. This condition is called scarlet fever. Scarlet fever is treated with antibiotics. This usually leads to a quick recovery. Scarlet fever is not dangerous if treated.
Symptoms of strep throat usually begin within 2 to 5 days after you come in contact with someone who has a strep infection. Strep throat usually goes away in 3 to 7 days with or without antibiotic treatment. In contrast, if allergies or irritants are the cause of your sore throat, it will usually last longer unless the cause is eliminated.
If strep throat isn't treated with antibiotics, you will continue to be contagious for 2 to 3 weeks even if your symptoms go away. You are much less contagious within 24 hours after you start antibiotics and are less likely to develop complications of the strep infection.
Complications of strep throat
Complications of strep throat are rare but can occur, especially if your throat infection isn't properly treated with antibiotics. Complications can occur when the strep infection spreads to other parts of the body and causes other infections, such as an ear or sinus infection or an abscess near the tonsils (peritonsillar abscess). Complications can also result in your immune system attacking itself and causing serious conditions such as rheumatic fever.
Treating strep throat can greatly reduce your risk for rheumatic fever and its complications. It is not clear whether treating the strep infection with antibiotics reduces your risk for inflammation of the kidneys (acute glomerulonephritis).
What Increases Your Risk
Your risk of getting strep throat increases if you come in close contact with others, especially children, who have a strep infection.
The size of a child's tonsils isn't a risk factor for throat infections. Children or adults who have had their tonsils removed can still get strep throat.
When To Call a Doctor
Call your doctor today if you have:
- A red rash that feels like sandpaper. This may indicate scarlet fever.
- Difficulty sleeping because your throat is blocked by swollen tonsils or adenoids.
Call a doctor if the following symptoms develop 1 to 2 weeks or longer after a strep throat infection. These symptoms may indicate rheumatic fever.
- Shortness of breath
- Joint pain
- Raised red rash or lumps under the skin
- Uncontrolled, jerking movements of the arms or legs
Call your doctor if your symptoms do not improve after 2 days of treatment with an antibiotic.
Watchful waiting is appropriate if your sore throat occurs with symptoms like those of a cold, such as sneezing, coughing, and a runny or stuffy nose. In general, the more of these symptoms you have, the less likely it is that your sore throat is caused by a strep infection. You can try home treatment if your sore throat is not severe and you have other symptoms of a cold.
For more information on what to do if you have sore throat symptoms, see the topic Sore Throat and Other Throat Problems.
Who to see
Your family doctor or general practitioner can evaluate a sore throat, do throat cultures or quick tests, and prescribe antibiotic treatment if needed. You may be referred to a specialist, such as a pediatrician for your child, or an otolaryngologist (ear, nose, and throat specialist).
If surgery to remove chronically enlarged or infected tonsils or adenoids is suggested, you may be referred to an otolaryngologist.
To prepare for your appointment, see the topic Making the Most of Your Appointment.
Examinations and Tests
Strep throat is diagnosed from your medical history, a physical examination of your throat, and a lab test, such as a throat culture. Sometimes a rapid strep test is used to check for strep. Your doctor may confirm the results of the rapid strep test with a throat culture.
Current treatment guidelines recommend that your doctor confirm strep throat with a lab test, such as a throat culture, and not just diagnose strep throat from your symptoms. But your doctor may begin treatment for strep throat before the result of your throat culture is back if you have three or four of the following symptoms:
- A recent fever of 38.3°C (101°F) or higher
- White or yellow spots or coating on the throat or tonsils
- Swollen or tender lymph nodes on the neck
- Absence of signs of a cold or upper respiratory infection, such as coughing or sneezing
One or both of the following tests are used to confirm that you have strep throat.
- Throat culture is a test to find germs (such as strep bacteria) that can cause an infection. A sample of cells from the back of your throat is added to a substance that promotes the growth of bacteria. If no bacteria grow, the culture is negative. If strep bacteria grow, the culture is positive.
- Rapid strep test analyzes the bacteria in your throat to see if strep is the cause of your sore throat. The doctor uses a cotton swab to gather cells from the back of your throat for testing. The rapid strep test is not used in many parts of Canada.
If symptoms of strep throat are present, it is important to be tested for strep infection. Prompt treatment will reduce the spread of strep throat and may reduce the risk of complications, such as the infection spreading to other parts of your body causing ear or sinus infections or an abscess behind or around your tonsils (peritonsillar abscess).
The rapid strep test is not used in many parts of Canada. If you need to be tested for strep throat and the rapid strep test is available, it may help to discuss with your doctor the advantages and disadvantages of each test. For instance, results from a rapid strep test are available within 10 to 15 minutes, and results from a throat culture may take 1 to 2 days. A throat culture is more accurate.
- A negative rapid strep test result can mean there are no strep bacteria present. But the rapid strep test can give negative results even when strep bacteria are present (false-negative test results). If the rapid strep test result is negative but strep throat is still suspected, your doctor may order a throat culture to verify the results.
- If the rapid strep test result is positive, a throat culture isn't needed. Antibiotic treatment can be started right away. Antibiotics may not make you well faster. But they shorten the time you are able to spread the disease to others. Antibiotics also lower the risk of spreading the infection to other parts of your body.
Testing is not needed:
- After antibiotic treatment, unless you still have symptoms. Testing may be done if symptoms return or you have had rheumatic fever and are at risk for it coming back.
- For a person who was exposed to strep but has no symptoms. For instance, family members of a person who has strep throat do not need to be tested unless they start to have symptoms.
It is possible for a person to carry the strep bacteria and not have any symptoms. If a number of infections occur in the same family, or if there have been severe complications such as rheumatic fever or toxic shock syndrome, it may be helpful to test family members to learn whether they are carriers of strep infection. But it is unusual for a person to catch strep throat from a carrier.
Antibiotics such as amoxicillin, cephalexin, or penicillin are used to treat strep throat. Antibiotics work only against bacterial infections such as strep throat. They will not help sore throats caused by allergies or viral infections such as colds.
Antibiotics are commonly used to:
- Kill the bacteria and shorten the time you are contagious. You are typically no longer contagious 24 hours after you start antibiotics.
- Prevent rare complications. Although uncommon, strep bacteria can spread to other parts of your body, causing ear or sinus infections or an abscess behind or around the tonsils (peritonsillar abscess). Antibiotics may also prevent the infection from triggering your immune system to attack itself and cause serious conditions such as rheumatic fever.
- Relieve discomfort and speed healing to some degree.
Antibiotic treatment can begin immediately if a strep infection is confirmed by a rapid strep test. But there is no harm in waiting for the results of a throat culture to confirm strep throat before starting antibiotic treatment. In fact, it is better to wait until strep throat has been confirmed so that antibiotics are not used unnecessarily. Overuse of antibiotics can make them ineffective.
Although waiting to treat strep throat may prolong the time you have the illness, delaying treatment for a few days doesn't increase the risk of rheumatic fever or other complications.
Your doctor also may recommend non-prescription medicines such as acetaminophen or anesthetic throat sprays to help relieve the pain and discomfort caused by strep throat. Acetaminophen will also reduce fever. Be safe with medicines. Read and follow all instructions on the label. Acetaminophen and ibuprofen are different products with different dosing recommendations. Talk to your child's doctor before switching back and forth between doses of acetaminophen and ibuprofen. When you switch between two medicines, there is a chance your child will get too much medicine. Studies have not shown any added benefit from alternating these medicines.
For more information, see:
To avoid getting strep throat, it is a good idea to avoid contact with anyone who has a strep infection.
- Bacteria are almost always transmitted by contact with tiny droplets from an infected person. Strep throat is passed from one person to another by contact with the tiny droplets of an infected person's cough, sneeze, or breath.
- Bacteria can also live for a short time on doorknobs, water faucets, and other objects. If you touch an infected object and then touch your eyes, nose, or mouth, you can become infected with the bacteria or virus.
- Bacteria can also be carried on food.
Keep up your body's resistance to infection with a good diet, plenty of sleep, and regular exercise. Managing stress can also strengthen your body's ability to fight off illness, such as strep throat.
Humidify your home during the dry winter months or year-round if you live in a dry climate. Moisture in the air (humidity) helps keep your mucous membranes moist and more resistant to bacteria. You can use a humidifier in the bedroom while you sleep. But use care if a person in the home has asthma or allergies, because mould or other particles that collect in the humidifier can make these conditions worse. Clean humidifiers on a regular basis.
Stop smoking, and avoid breathing others' smoke. Smoke irritates the throat tissues and may make you more likely to get infection.
Your doctor may have prescribed an antibiotic for strep throat. Take all of the antibiotic exactly as prescribed. This will help prevent the infection from coming back and will prevent complications of infection that could occur if you do not take the medicine as prescribed.
There are many ways that you can make yourself feel better while you are waiting for the strep infection to go away.
- Drink plenty of fluids and increase humidity (moisture in the air) in your home to help keep your throat moist. Herbal teas formulated for colds may help relieve symptoms.
- Get plenty of rest. Stay home the first day of antibiotic treatment. You are still contagious and might pass the infection to others. Rest in bed if you feel very sick. Bedrest is not required if you feel fine.
- Take non-prescription medicines to relieve a painful sore throat and reduce fever. Be safe with medicines. Read and follow all instructions on the label.
- Try an over-the-counter anesthetic throat spray or throat lozenges, which may help relieve throat pain. Do not offer throat lozenges to young children as they are a choking hazard. If your child is younger than age 2, ask your doctor if you can give your child numbing medicines.
For more information on non-prescription medicines and other ways to relieve sore throat symptoms, see the topic Strep Throat: Home Treatment.
For the first 24 hours after you start taking an antibiotic, you are still contagious. You can avoid passing the strep throat infection to others and reinfecting yourself by:
- Avoiding sneezing or coughing on others.
- Washing your hands often.
- Using tissues you can throw away, not handkerchiefs.
- Using a new toothbrush as soon as you feel sick. Replace it again when you are well. You can also clean your toothbrush well before using it again. Bacteria can collect on the bristles and reinfect you.
Antibiotics are the treatment of choice for a confirmed strep throat infection.
- Antibiotics will reduce the time you are contagious. You are usually not contagious 24 hours after starting antibiotics.
- Antibiotic treatment for strep throat can also help prevent some of the rare complications related either to the strep infection itself or to the body's immune response to the infection. Complications of strep throat are rare but can occur, especially if strep throat is not properly treated.
- Antibiotics may shorten the time you are sick by about one day.
When antibiotics may be used
Antibiotics may be used in the following situations:
- You have had a positive rapid strep test or positive throat culture.
- You have three or more of the following
signs or symptoms:
- A recent fever
- White or yellow spots or coating on the throat or tonsils
- Swollen or tender lymph nodes on the neck
- Absence of signs of a cold or other upper respiratory illness, such as coughing or sneezing
- You have recently had rheumatic fever and have been exposed to strep. Preventive antibiotics may be given in some cases.
- Several family members are having repeated strep infections as confirmed by positive throat cultures.
It is possible for you to carry the strep bacteria in the throat and not have any symptoms. Antibiotics for the carrier state are usually not needed unless you have a history of rheumatic fever or frequent infections or infections are occurring frequently in the family.
For more information, see:
Antibiotics such as amoxicillin, cephalexin, or penicillin are used to treat strep throat infection.
What to think about
Immediate treatment with an antibiotic after a positive rapid strep test may not make you well faster. But it will shorten the time you are able to spread the disease to others. Antibiotics also lower the risk of the infection spreading to other parts of your body. But there is no harm in delaying medicine treatment 1 to 2 days to wait for the results of a throat culture. Antibiotics will prevent rheumatic fever even if it is started up to 9 days after symptoms begin.
If strep throat continues to recur, you and your doctor may decide that you need surgery to remove the tonsils (tonsillectomy). Surgery is considered when you:
- Have recurring episodes of strep throat or tonsillitis in a single year despite antibiotic treatment.
- Have abscesses around the tonsils that do not respond to drainage, or if an abscess is present in addition to other signs that you may need tonsillectomy.
- Have persistent bad odour or taste in the mouth, which is caused by tonsillitis that does not respond to antibiotics.
- Need a biopsy to evaluate a suspected tumour of the tonsil.
Large tonsils are not an indication for tonsillectomy unless they are causing one of the above problems or they are blocking the upper airway, which can cause sleep apnea or problems with eating.
Tonsillectomy may be done in some cases of strep throat.
An abscess around the tonsils (peritonsillar abscess) may be treated with a simple procedure in which a small incision is made to drain the abscess, although removing the tonsils is appropriate in some of these cases.
What to think about
Tonsillectomy is no longer routine for children who have frequent sore throats. Surgery has been shown to reduce the number of throat infections for 2 years. But over time many children who did not have surgery also had fewer throat infections.footnote 1
When you are trying to decide whether to have your or your child's tonsils removed, consider:
- How much time you or your child is missing from work or school because of throat infections.
- How much stress and inconvenience the illness places on the family.
The risks of surgery must also be weighed against the risks of leaving the tonsils in. In some cases of persistent strep throat infections, especially if there are other complications, surgery may be the best choice.
Other Places To Get Help
- Baugh RF, et al. (2011). Clinical practice guideline: Tonsillectomy in children. Otolaryngology-Head and Neck Surgery, 144(IS): S1-S30.
Other Works Consulted
- American Academy of Pediatrics (2015). Group A streptococcal infections. In LK Pickering et al., eds., Red Book: 2015 Report of the Committee on Infectious Diseases, 28th ed., pp. 616-628. Elk Grove Village, IL: American Academy of Pediatrics.
- American Heart Association (2009). Prevention of rheumatic fever and diagnosis and treatment of acute streptococcal pharyngitis: A scientific statement from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee of the Council on Cardiovascular Disease in the Young, the Interdisciplinary Council on Functional Genomics and Translational Biology, and the Interdisciplinary Council on the Quality of Care and Outcomes Research: Endorsed by the American Academy of Pediatrics. Circulation, 119(11): 1541-1551.
- American Public Health Association (2015). Streptococcal diseases. In DL Heymann, ed., Control of Communicable Diseases, 20th ed., pp. 581-592. Washington, DC: American Public Health Association.
- Kenealy T (2014). Sore throat. BMJ Clinical Evidence. http://clinicalevidence.bmj.com/x/pdf/clinical-evidence/en-gb/systematic-review/1509.pdf. Accessed March 21, 2014.
- Low DE (2016). Nonpneumococcal infections and rheumatic fever. In L Goldman, A Shafer, eds., Goldman-Cecil Medicine, 25th ed., vol. 2, pp. 1906-1913. Philadelphia: Saunders.
- Wessels MR (2011). Streptococcal pharyngitis. New England Journal of Medicine, 364(7): 648-655.
- Wessels MR (2015). Streptococcal infections. In DL Kasper et al., eds., Harrison's Principles of Internal Medicine, 19th ed., vol. 2, pp. 963-971. New York: McGraw-Hill Education.
Adaptation Date: 12/3/2017
Adapted By: HealthLink BC
Adaptation Reviewed By: HealthLink BC
Adaptation Date: 12/3/2017
Adapted By: HealthLink BC
Adaptation Reviewed By: HealthLink BC
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