Fever and sore throat: when is a strep test helpful?

Hello. I am Shunichi Gamo, MD, PhD, a board-certified pulmonologist and the director of Sendai International Airport North Clinic.

When a fever comes on suddenly and even swallowing your saliva hurts, many people wonder whether it might be strep and whether they should get tested. This article explains how often strep is the cause of fever and sore throat, and when a strep test is helpful and when it is not needed. It also explains what to do after you get your test result, and the signs that mean you need to see a doctor urgently.

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Is strep the only cause of fever and sore throat?

Most cases of fever and sore throat are caused by viruses, and only some are caused by strep (formally called group A beta-hemolytic streptococcus, a type of bacterium). According to a 2023 US report, 70% to 95% of tonsillitis cases (when the tonsils, on both sides of the back of the throat, become swollen and painful) are caused by viruses. [1] Strep causes 5% to 15% of tonsillitis in adults, and 15% to 30% of tonsillitis in children aged 5 to 15. [1]

When a virus is the cause, the illness often gets better on its own, but when bacteria are the cause, antibiotics (medicines that fight bacteria) may be needed. [2] In practice, according to a 2024 US review article (a paper that summarizes the research on a topic), strep is the cause in only 10% of adults who see a doctor for a sore throat. [3] A 2023 study that compared 19 clinical guidelines (recommendations for doctors on how to treat patients) reports that, in children, about 25% of sore throats are caused by strep. [4]

Group	Share by cause (2023 sources)
All tonsillitis	Of all tonsillitis, 70% to 95% is caused by viruses. [1]
Tonsillitis in adults	Of tonsillitis in adults, 5% to 15% is caused by strep. [1]
Tonsillitis at ages 5 to 15	Of tonsillitis in children aged 5 to 15, 15% to 30% is caused by strep. [1]
Children (all sore throats)	Of sore throats in children, about 25% are caused by strep. [4]

Even if you have leftover antibiotics from before, please do not take them on your own. First, see a doctor to find out what is causing your symptoms.

What symptoms suggest strep? How is it different when there is a cough?

Even experienced doctors can find it hard to tell strep apart from other causes by symptoms alone. [5] During the exam, the doctor looks at several clues together. These include whether there is a coating on the tonsils (whitish, pus-like material), whether the lymph nodes in the neck are swollen, and whether you have a cough. The table below summarizes these clues and what they may mean.

In children, a strep throat infection typically causes a sudden fever, a very sore throat and pain when swallowing. [5] Red, swollen tonsils and swollen lymph nodes at the front of the neck that hurt when pressed are also common. [5] The Infectious Diseases Society of America’s 2025 guideline discusses a method that turns symptoms and exam findings into a score to estimate the chance of strep. [6] Items used in the score include fever, swollen tonsils or a coating on the tonsils, the swollen neck lymph nodes mentioned above, and the absence of a cough. [6] This method was reported to be as accurate as, or slightly more accurate than, a doctor’s judgment alone. [6] However, the studies it is based on have limitations, such as their small size. [6]

Clue found during the exam	What it may mean
Fever, a coating on the tonsils, swollen lymph nodes in the neck	In people who see a doctor for fever and sore throat, having a fever, a coating on the tonsils and swollen lymph nodes in the neck makes strep more likely. [3]
Age 3 to 15	In people who see a doctor for fever and sore throat, being aged 3 to 15 is one clue that points to strep, together with other findings. [3]
A cough	In people who see a doctor for fever and sore throat, having a cough makes a virus a more likely cause than strep. [3]
Sudden fever, pain when swallowing, red and swollen tonsils	In children, a strep throat infection typically causes a sudden fever, pain when swallowing and red, swollen tonsils. [5]

When you see the doctor, tell them whether you have a cough and the day you first noticed a lump in your neck.

When should you get a strep test?

A strep test is helpful when your symptoms and age suggest strep is possible, and a decision is needed on whether to use antibiotics. [3][2] According to a 2024 US review article, clinical guidelines recommend first estimating the chance of strep from symptoms, age and other factors. [3] Then, if it is still unclear, they recommend a rapid antigen test (a test that looks for parts of the strep bacterium in a throat sample) before antibiotics are prescribed. [3] When strep is not suspected, based on symptoms and other factors such as whether strep is going around near you, testing is generally not considered necessary. [5]

A 2020 Canadian review article states that a rapid antigen test should be used only when the question is whether to start antibiotics. [2] Testing everyone puts a burden of cost and effort on people who are unlikely to have strep. [6] For this reason, the Infectious Diseases Society of America’s 2025 guideline states that the main role of scoring is to identify people who are unlikely to have strep and to reduce unnecessary testing. [6]

Situation	Role of testing
There are signs that suggest strep, such as fever or a coating on the tonsils, but the diagnosis is still unclear	A 2024 US review article recommends a rapid antigen test before antibiotics are prescribed. [3]
Strep is not suspected, based on symptoms and whether strep is going around near you	In this case, not testing is also an option. If no test is done, please ask the doctor why during your visit.
Symptoms and findings are turned into a score to estimate the chance of strep	The Infectious Diseases Society of America’s 2025 guideline states that the main role of scoring is to identify people who are unlikely to have strep and to reduce unnecessary testing. [6]

If a test is recommended, ask how your treatment would differ depending on the result.

What kinds of strep tests are there? Rapid antigen test vs. culture

A 2024 review article on strep infections in children and teenagers lists three types of tests that can confirm strep. [5] They are the rapid antigen test, culture (a test that grows the bacteria in a sample to identify them) and molecular tests (tests that check for strep genes on the spot). [5] All of them use a sample collected by rubbing a swab against the back of the throat. [5] A 2024 US review article recommends confirming with a culture when a child or teenager has a negative rapid antigen test. [3] However, policies on whether to add a culture after a negative result differ by country and by medical facility.

Rapid antigen tests and cultures are used together with the symptoms and findings from the exam to identify the cause. [2] For people who may have strep, confirming the diagnosis with these tests before starting antibiotics is recommended. [5]

Test	How it works
Rapid antigen test	A rapid antigen test detects parts of the strep bacterium in a throat swab sample. [5]
Culture	The bacteria in the sample are grown to check whether they are strep. [5]
Molecular test	A molecular test detects strep genes in a throat swab sample. [5]

Write down the name of the test you had and its result before you forget.

If your strep test is positive, do you need antibiotics?

When a positive strep test confirms the infection, starting antibiotic treatment without delay is recommended. [5] The goal of early diagnosis and treatment is to prevent complications (other illnesses that follow the first one). [5] These complications include inflammation of the neck lymph nodes, peritonsillar abscess (a collection of pus around the tonsils) and, above all, rheumatic fever (inflammation of the heart and other organs after a strep infection). [5] Treatment is also expected to ease symptoms, shorten the illness and reduce spread to others. [5]

The first choice is a penicillin-type antibiotic, and people who are allergic to penicillin are given a different type of antibiotic. [5][4] If symptoms get worse after starting antibiotics, or if they are still present 5 days after the start of treatment, seeing a doctor again is recommended. [3]

Views on how widely to use antibiotics differ from country to country. [4] A 2023 study that compared 19 guidelines found three different approaches. [4] One uses antibiotics to prevent rheumatic fever, one uses them only in limited cases, and one decides based on each patient’s risk of rheumatic fever. [4]

Even if your symptoms get better, do not stop the prescribed antibiotics on your own. Take them for the full number of days your doctor told you.

Fever and sore throat: which signs mean you need to see a doctor urgently?

If, along with fever and sore throat, you have trouble opening your mouth, cannot swallow, or your voice sounds muffled, seek medical care right away, even at night or on a weekend or holiday. If you have trouble breathing, or you cannot swallow your saliva and are drooling, do not hesitate to call 119 (Japan’s emergency number for an ambulance).

Peritonsillar abscess (a collection of pus around the tonsils) is the most common deep infection of the head and neck, and it mainly affects young adults. [7] Typical symptoms are fever, sore throat, trouble swallowing, trouble opening the mouth and a muffled voice. [7] A peritonsillar abscess can lead to serious complications, such as blockage of the airway (the passage that air travels through). [7] For this reason, it is important to find it early and start treatment. [7]

A strep infection can lead to complications such as an abscess (a collection of pus), rheumatic fever, acute glomerulonephritis (kidney inflammation) and scarlet fever (an illness with a red rash all over the body). [1] Because of these risks, it is important to tell strep apart from other causes. [1] Complications of tonsillitis are more likely the younger the patient is. [8] To prevent retropharyngeal abscess (a collection of pus behind the back wall of the throat) and rheumatic fever, it is important to consider the possibility of strep tonsillitis and, when needed, start antibiotics without delay. [8]

Situation	What to do
Trouble breathing, or unable to swallow saliva and drooling	A peritonsillar abscess can lead to a complication that blocks the airway. [7] Call 119 right away.
Trouble opening the mouth, unable to swallow, or a muffled voice	These match the typical symptoms of a peritonsillar abscess. [7] Seek medical care, even at night.
Unable to drink fluids, passing little urine, or limp and listless	Seek medical care the same day. If the person is limp and slow to respond when spoken to, seek medical care right away, even at night or on a weekend or holiday.
Getting worse despite starting antibiotics, or symptoms continuing 5 days after the start of treatment	A 2024 US review article recommends seeing a doctor again in this case. [3] If you have symptoms from the rows above, follow the guidance in those rows. If not, see a doctor during regular clinic hours.
None of the symptoms above, and able to drink fluids	You do not need to see a doctor urgently. But if the fever and sore throat continue, see a doctor during regular clinic hours and ask about testing. For tonsillitis caused by a virus, treatment centers on pain relief medicine and fluids. [8] If signs of getting worse appear, seek medical care at that point.

If you need care at night or on a weekend or holiday, call ahead to describe your symptoms and confirm which medical facility can see you before you go.

When you get a strep test, what should you tell the doctor?

Tell the doctor the day the fever started, whether you have a cough, any lumps in your neck or pain when you press on them, and whether illness is going around near you. These help the doctor decide whether a strep test is needed. Scoring methods that estimate the chance of strep use items such as fever, whether there is a cough, swollen and tender lymph nodes in the neck, and the condition of the tonsils. [6] The doctor can check the tonsils during the exam, so tell them about the symptoms you noticed yourself, along with the day each one started.

If you have ever had an allergic reaction to a penicillin-type medicine, be sure to say so at your visit, because a different medicine will need to be chosen. If you keep getting sore throats, also tell the doctor how many you had in each year over about the past 3 years.

A 2024 US review article gives the following numbers as a guide for when to consider a tonsillectomy (surgery to remove the tonsils). [3] They are 7 strep throat infections in 1 year, 5 a year for 2 years in a row, or 3 a year for 3 years in a row. [3] However, the same review states that surgery to prevent infections is rarely recommended. [3] Guidance on when to consider surgery differs by country and by medical facility.

What to tell the doctor	Why it helps
Whether you have a fever, and the day it started	When the chance of strep is estimated with a score, whether there is a fever is one of the items. [6] Telling the doctor the day the fever started also makes it easier for them to understand how your illness has progressed.
Whether you have a cough	When the chance of strep is estimated with a score, the absence of a cough is also one of the items. [6]
Lumps in the neck, or pain when you press on them	When the chance of strep is estimated with a score, swollen lymph nodes in the neck that hurt when pressed are one of the findings checked. [6]
Illness going around nearby (family or school)	Please also tell the doctor whether illness is going around in your family or at school. It helps the doctor decide whether to suspect strep.
Drug allergies	If strep is confirmed and antibiotics are used, a penicillin allergy changes which medicine is chosen. [5]
How many times you have had a sore throat	The number of strep throat infections per year is used as a guide when considering a tonsillectomy. [3]

Before your visit, write these down in a notes app on your smartphone, and simply show them to the doctor in the exam room.

Summary

• Most cases of fever and sore throat are caused by viruses, and strep causes only some of them.
• A strep test is helpful when your symptoms and age suggest strep is possible, and a decision is needed on whether to use antibiotics.
• When strep is confirmed, antibiotic treatment is recommended. Even if your symptoms go away, do not stop the antibiotics partway; take them all. If you get worse after starting them, or if symptoms continue 5 days after the start of treatment, see a doctor again.
• If you have trouble opening your mouth, cannot swallow, or your voice sounds muffled, or if you have trouble breathing, see a doctor urgently (see the table in the article for guidance).
• At your visit, tell the doctor the day the fever started and whether you have a cough. Also mention any lumps in your neck or pain when you press on them, any illness going around near you, and any drug allergies. If you keep getting sore throats, also tell the doctor how many you had each year.

Frequently asked questions

Can adults get strep too?

Adults can get it too, but strep causes a somewhat smaller share of tonsillitis in adults than in children. In a 2023 report from the US, strep caused 5% to 15% of tonsillitis in adults, compared with 15% to 30% in children aged 5 to 15. [1] If you have a fever and a coating on your tonsils (whitish, pus-like material) but no cough, talk with your doctor about whether to get tested, even as an adult.

If my strep test is negative, does that mean I don’t need antibiotics?

A 2024 US review article recommends confirming with a culture when a child or teenager has a negative rapid antigen test. [3] How a negative result is handled differs by country and by medical facility. If the fever or sore throat gets worse after you are told the result is negative, see a doctor again. If you can no longer drink fluids, seek medical care the same day.

If my child is diagnosed with strep, when can they go back to school or daycare?

The Japan Pediatric Society gives guidance in its “Guide to Infectious Diseases to Be Prevented at Schools, Kindergartens, Certified Centers for Early Childhood Education and Care, and Nursery Schools” (revised April 2025). It states that a child stops being contagious within 24 hours of starting appropriate antibiotic treatment, so after that the child can return to school or childcare. However, the same guide states that a child with severe whole-body symptoms needs to rest while their condition is monitored. Depending on the circumstances, your child may be told to stay home from school or childcare for a period. Please tell the childcare center or school the day your child was diagnosed and the date and time they started antibiotics.

I get a fever and sore throat every year. Do I need surgery to remove my tonsils?

A 2023 report from the US strongly recommends watchful waiting (monitoring without surgery) if repeated tonsillitis happens less often than a certain number of times. [1] The guide is: fewer than 7 times in the past year, fewer than 5 a year for 2 years in a row, or fewer than 3 a year for 3 years in a row. [1] This guide is from the US, and views differ by country and by medical facility. When you talk with your doctor about surgery, tell them, as best you can, how many times a year you have had fever and sore throat.

Disclaimer

This article provides general medical information. It does not replace an examination, diagnosis or treatment by a doctor. The content is based on medical knowledge at the time of publication, but the right approach differs with each patient’s condition and background.

If you are worried about your symptoms, please talk to your regular doctor or a specialist medical facility.

References

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3. Hamilton JL, McCrea Ii L. “Streptococcal Pharyngitis: Rapid Evidence Review.” Am Fam Physician, 2024 Apr; 109(4): 343-349. PMID: 38648833
4. Pellegrino R, Timitilli E, Verga MC, Guarino A, Iacono ID, Scotese I, et al. “Acute pharyngitis in children and adults: descriptive comparison of current recommendations from national and international guidelines and future perspectives.” Eur J Pediatr, 2023 Dec; 182(12): 5259-5273. DOI: 10.1007/s00431-023-05211-w PMID: 37819417
5. Leung AKC, Lam JM, Barankin B, Leong KF, Hon KL. “Group A β-hemolytic Streptococcal Pharyngitis: An Updated Review.” Curr Pediatr Rev, 2024; 21(1): 2-17. DOI: 10.2174/1573396320666230726145436 PMID: 37493159
6. Linder JA, Watson ME, Wessels MR, Carter DM, Cohen AL, Dien Bard J, et al. “2025 Clinical Practice Guideline Update by the Infectious Diseases Society of America on Group A Streptococcal Pharyngitis: Risk Assessment Using Clinical Scoring Systems in Children and Adults.” Clin Infect Dis, 2026 Aug 24; 82(Suppl 3): i97-i104. DOI: 10.1093/cid/ciaf668 PMID: 41343363
7. Galioto NJ. “Peritonsillar Abscess.” Am Fam Physician, 2017 Apr 15; 95(8): 501-506. PMID: 28409615
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