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Health education · InfectionsCare and treatments

Sore throat and strep: understanding the causes, tests and treatments

A sore throat does not automatically mean a strep infection. Most cases of pharyngitis and tonsillitis are caused by viruses.1,2

Recognizing the symptoms, understanding what tests are for and knowing the warning signs help you seek care at the right time and use antibiotics when they are needed.

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Causes

What causes a sore throat?

Several situations can cause pain, irritation or a burning feeling in the throat.

CauseWhat to understand
A viral infectionRespiratory infection viruses, such as the common cold, can cause a sore throat. The Epstein-Barr virus, which causes mononucleosis, is another possible cause.3
A bacterial infectionGroup A streptococcus is the main bacterium involved. It causes about 20 to 30% of pharyngitis cases in children and 5 to 15% in adults.1,2
IrritationSmoke, dust and other irritants can also cause or prolong throat pain.5

Treatment depends on the cause: an antibiotic does not work against a virus or a simple irritation.1

The bacterium

What is group A streptococcus?

Group A streptococcus, also called Streptococcus pyogenes, is a bacterium that can infect the throat and tonsils.

This infection mainly affects school-age children, aged 5 to 15. It is less common in adults and rare as pharyngitis in children under three.4,3

Close contact with an infected person is the main risk factor for transmission, especially in families, schools and daycares.4

Symptoms

What symptoms can suggest strep?

These signs are not enough to confirm that strep is present.

A strep throat infection can cause, among other things:1,2

  • a sore throat that starts suddenly;
  • pain when swallowing;
  • fever;
  • tender lymph nodes in the neck;
  • red or swollen tonsils, sometimes with whitish patches;
  • nausea, vomiting or a stomach ache, especially in children.

What signs point more to a viral infection?

A cough, runny nose, hoarse voice, conjunctivitis or mouth ulcers point more toward a viral cause.4,2

Without obvious viral signs, the appearance of the throat alone cannot distinguish a viral infection from a strep infection.4

Testing

Is a strep test always needed?

No. The test is chosen based on symptoms and the clinical assessment.2

The professional considers, among other things, age, fever, whether there is a cough, the lymph nodes and the appearance of the tonsils. A clinical tool, the modified Centor score, helps decide whether a swab is worthwhile.6

The goal is to test people in whom a strep infection is likely enough. In Quebec, this test is for people aged 3 and older.6,3

How is the swab done?

A swab is passed over the tonsils and the back of the throat. The sample can be used for different tests, depending on what is available:6

A rapid test

It looks for strep and gives a result quickly.

A throat culture

It is done in a laboratory and the result takes longer.

A molecular test

It detects the bacterium’s genetic material.

Does a negative rapid test always rule out strep?

Not necessarily: it depends on the type of test.

According to the INESSS Quebec protocol, a negative rapid antigen test must be followed by a culture in children under 15, in people who have already had a strep complication (such as acute rheumatic fever) and in people living in an Indigenous community.6

A molecular test is more sensitive: according to INESSS, a negative result does not need to be confirmed.7 The professional decides whether confirmation is needed.

Treatment

How is a sore throat treated?

When it is caused by a virus

Antibiotics are not useful. Care mainly aims to relieve pain, maintain hydration and allow rest.

Most viral pharyngitis gets better on its own in 3 to 5 days.1

When a strep infection is confirmed

An antibiotic is generally indicated. It reduces transmission, lowers the risk of some complications and shortens symptoms by about one day.1,2

Take the dose and duration prescribed, even if you feel better. Do not share antibiotics and do not use an old treatment without an assessment.9

At home

How to relieve symptoms at home?

A few simple measures improve comfort.5,8

Drink regularly

Hot or cold drinks, whichever feels better.

Eat soft foods

Soups, purées, eggs, yogurt: foods that are easy to swallow.

Rest

Rest helps the body recover.

Avoid irritants

Smoke, dust, citrus juices and alcohol.

Gargle

With warm salt water, for adults and children who can gargle without swallowing.

Relieve pain

With a medication suited to age and health.

Acetaminophen or ibuprofen may be suggested depending on the situation. Ibuprofen is contraindicated in babies under six months. Lozenges and ice cubes are recommended only from age 4. Ask a pharmacist if in doubt.5

For children: the comic « Clara and the sore throat »

Complications

What complications can occur?

Acute rheumatic fever and glomerulonephritis occur after the infection, because of the immune response. Antibiotics reduce the risk of acute rheumatic fever, but the evidence does not show that they prevent glomerulonephritis.4,10,2

Strep complications are rare, but they can include:3,4

  • an abscess around a tonsil or in the deep tissues of the throat;
  • acute rheumatic fever, an inflammatory reaction that can affect the heart and joints in particular;
  • kidney inflammation called post-streptococcal glomerulonephritis.

What about scarlet fever?

A strep infection can come with a red rash, with very rough skin that feels like sandpaper, and sometimes a red tongue that looks like a raspberry.5,8

A sore throat with this rash should be assessed.5

When to seek care

When should you seek care?

While on antibiotics

Contact a professional again if there is no improvement after 48 to 72 hours of treatment, or sooner if things get worse.6

An assessment is recommended in particular when:5,8

  • the pain has lasted more than three days without improvement;
  • a sore throat, fever and difficulty swallowing appear after contact with someone who has a strep infection;
  • the skin changes colour or becomes very rough, like sandpaper;
  • the fever does not come down despite medication;
  • a person aged 75 or older has difficulty doing one or two daily activities;
  • the symptoms get worse.

When should you go to the emergency room?

Do not wait for a simple strep test if there is:5

  • difficulty breathing;
  • inability to swallow water or your own saliva;
  • drooling because swallowing is impossible;6
  • unusual drowsiness, confusion or rapid deterioration;
  • significant signs of dehydration.

Very severe pain on one side, difficulty opening the mouth, swelling or stiffness of the neck, or a muffled voice also need urgent assessment.6

In respiratory distress or immediate danger, call 911. For guidance based on your symptoms, call Info-Santé at 811, option 1.5

Transmission

How to limit transmission?

Washing your hands often and not sharing objects that have been in contact with the sick person’s mouth help limit the spread. It is also recommended to change your toothbrush 24 hours after starting antibiotics.8

When a strep infection is confirmed, the Quebec protocol allows a return to school or daycare after 24 hours of treatment, depending on general condition.6,3 Fever or still feeling very unwell may mean staying home longer.

When to consult at the Clinique IPS du Palais?

Sore throats are among the common health problems the clinic can assess, according to the applicable clinical criteria. A nurse practitioner can examine the throat, decide whether a test is worthwhile and suggest suitable treatment, within the limits of her scope of practice.

Sore throat is also one of the examples of reasons for a teleconsultation at the clinic, with a photo sent in. If you have warning signs, go to the emergency room without waiting.

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FAQ

Frequently asked questions

Do white spots always mean strep?

No. The appearance of the tonsils alone cannot confirm the cause. A test may be needed depending on the assessment.4

Can you test positive without being sick?

Yes. Some people carry strep without symptoms. They generally do not need treatment.11 This is another reason to choose tests carefully and interpret results in context.

Should a child under 3 be tested?

Generally not: strep pharyngitis is rare at that age and the test is for people aged 3 and older.4,6 A child under 3 with a sore throat and fever should still be assessed based on their symptoms.

Sources

  1. Government of Quebec. Pharyngite ou amygdalite à streptocoque A, Québec.ca (in French). Updated April 22, 2024, accessed October 29, 2026. quebec.ca
  2. Institut national d’excellence en santé et en services sociaux (INESSS). Pharyngite-amygdalite chez l’enfant et l’adulte, optimal use guide (in French). March 2016, updated September 2017, accessed October 29, 2026. inesss.qc.ca
  3. Ministère de la Santé et des Services sociaux. Prévention et contrôle des infections dans les services de garde et écoles du Québec – Guide d’intervention, chapter 6 (in French). September 2024, accessed October 29, 2026. msss.gouv.qc.ca
  4. Centers for Disease Control and Prevention (CDC). Clinical Guidance for Group A Streptococcal Pharyngitis. November 18, 2025, accessed October 29, 2026. cdc.gov
  5. Santé Québec. Mal de gorge (health advice, in French). Updated September 22, 2026, accessed October 29, 2026. sante.quebec
  6. INESSS. Protocole médical national : pharyngite-amygdalite (No. 888054, in French). June 2025, accessed October 29, 2026. inesss.qc.ca
  7. INESSS. Initier une mesure diagnostique et thérapeutique chez une personne qui présente des signes et symptômes de pharyngite-amygdalite, supporting report (in French). June 2025, accessed October 29, 2026. inesss.qc.ca
  8. Santé Québec. Streptocoque (health advice, in French). Updated September 22, 2026, accessed October 29, 2026. sante.quebec
  9. Health Canada. Ce que vous devez savoir au sujet des médicaments antimicrobiens, y compris les antibiotiques (French version of the fact sheet). Modified December 17, 2024, accessed October 29, 2026. canada.ca
  10. CDC. Clinical Guidance for Post-Streptococcal Glomerulonephritis. August 5, 2025, accessed October 29, 2026. cdc.gov
  11. Shulman ST, Bisno AL, Clegg HW, Gerber MA, Kaplan EL, Lee G, Martin JM, Van Beneden C. Clinical Practice Guideline for the Diagnosis and Management of Group A Streptococcal Pharyngitis: 2012 Update by the Infectious Diseases Society of America. Clinical Infectious Diseases, 2012, accessed October 29, 2026. doi.org

This sheet provides general information and does not replace an assessment by a health professional. Published October 29, 2026.