Strep throat

Strep throat is a bacterial infection of the throat and tonsils caused by group A Streptococcus (Streptococcus pyogenes). It is most common in school-age children but can affect people of any age. Symptoms include sudden sore throat, pain with swallowing, fever, and swollen lymph nodes without the cough and runny nose typical of viral colds.

Because strep throat can lead to complications such as rheumatic fever if untreated (particularly in some populations), confirming the diagnosis with a rapid test or culture and treating with antibiotics is important. Most people feel better within a day or two of starting antibiotics and are less contagious after 12–24 hours of treatment.

Classic features of strep throat include:

• Sudden onset of sore throat
• Painful swallowing
• Fever
• Red and swollen tonsils, sometimes with white patches or streaks of pus
• Tiny red spots on the soft or hard palate (petechiae)
• Swollen, tender lymph nodes in the neck
• Headache, abdominal pain, nausea, or vomiting (especially in children)
• Body aches and fatigue
• In some cases, a sandpaper-like rash of scarlet fever

Cough, runny nose, hoarseness, and pink eye suggest a viral cause more than strep.

Strep throat is caused by group A Streptococcus bacteria. It spreads through respiratory droplets from coughing, sneezing, or shared food and drinks. People are most contagious when symptomatic and remain so until treated with appropriate antibiotics for at least 12–24 hours. Asymptomatic carriers exist but are less likely to spread disease or develop complications.

Risk is highest in:

• School-age children (5–15 years)
• Parents and others in close contact with school-age children
• Crowded settings (schools, daycare, military barracks)
• Seasonal peaks in late autumn, winter, and early spring in many climates

Complications of untreated or incompletely treated strep throat can include:

• Peritonsillar or retropharyngeal abscess
• Otitis media and sinusitis
• Scarlet fever
• Post-streptococcal reactive arthritis
• Rheumatic fever (can damage the heart) — now uncommon in many high-resource settings but still important globally
• Post-streptococcal glomerulonephritis
• Invasive disease (rare) such as bacteremia or necrotizing fasciitis
• PANDAS/PANS — controversial pediatric neuropsychiatric associations under study

Reduce spread by:

• Washing hands frequently
• Covering coughs and sneezes
• Not sharing utensils, drinks, or toothbrushes
• Staying home from school or work until fever-free and on antibiotics for at least 12–24 hours
• Replacing toothbrush after starting antibiotics (optional but commonly advised)

Because viral pharyngitis is much more common than strep, testing is used to confirm bacterial infection before antibiotics:

• Rapid antigen detection test (RADT) from a throat swab — results in minutes
• Throat culture — more sensitive; used to confirm negative rapid tests in children and adolescents
• Molecular tests in some settings

Testing is generally not needed when viral features (cough, runny nose, hoarseness, oral ulcers) predominate. Centor or McIsaac scores can help estimate probability and guide testing decisions in adults.

See a clinician for a sore throat with fever, swollen lymph nodes, or rash — especially in children — or if symptoms are severe or last longer than a few days. Seek urgent care for difficulty breathing or swallowing, severe drooling, neck stiffness, or a muffled “hot potato” voice, which may indicate a deeper infection such as peritonsillar abscess.

Confirmed strep throat is treated with antibiotics to shorten symptoms slightly, reduce contagiousness, and prevent rheumatic fever:

• Penicillin or amoxicillin for 10 days remains first-line for most patients without allergy
• Intramuscular benzathine penicillin G as a single dose when adherence is a concern
• For penicillin allergy: cephalexin, cefadroxil, clindamycin, azithromycin, or clarithromycin depending on allergy type and local resistance
• Complete the full course even if symptoms resolve quickly
• Pain relief with acetaminophen or ibuprofen; throat lozenges and soft foods for comfort
• Corticosteroids are sometimes used as an adjunct for severe symptoms under clinician judgment

Follow-up testing is not routinely needed if symptoms resolve.

While recovering:

• Take all prescribed antibiotics
• Rest and drink plenty of fluids
• Use pain relievers as directed
• Gargle with warm salt water; use throat lozenges if age-appropriate
• Choose soft, easy-to-swallow foods
• Use a humidifier if air is dry
• Stay home until fever is gone and antibiotics have been taken for at least 12–24 hours

Bring:

• Symptom onset and associated features (fever, rash, cough, runny nose)
• Exposure to known strep cases
• Antibiotic allergies
• Prior episodes of strep throat
• Questions about testing, antibiotic choice, and when return to school is safe