Yes, Group C Streptococcus (strep C) is contagious. It spreads between people through many of the same routes as the more familiar Group A strep, including respiratory droplets, direct skin contact, and shared food or drinks. While strep C causes a smaller share of sore throats than Group A, it produces nearly identical symptoms and can lead to serious complications if untreated.
How Strep C Spreads
Strep C passes from person to person through:
- Coughing and sneezing
- Skin-to-skin contact
- Sharing food, drinks, utensils, or cups
- Contaminated food, particularly unpasteurized dairy products
- Surgical wounds
- From mother to baby during childbirth
A person with strep C typically stops being contagious within 12 hours of starting antibiotics. Before treatment, or without it, the bacteria can spread for as long as symptoms last. Schools and child care centers generally follow the same exclusion rule used for Group A strep: children and staff should stay home until they’ve been on antibiotics for at least 12 hours.
Animal-to-Human Transmission
Unlike Group A strep, which only infects humans, some strep C species also live in animals. Zoonotic infections have been reported in people who work closely with farm animals, especially horses. Several documented outbreaks have been traced to unpasteurized or inadequately pasteurized dairy products, including one linked to fresh goat cheese. That said, the strains of strep C adapted to humans are genetically distinct from animal strains, and cross-species transmission is uncommon.
How Common Is Strep C?
Strep C accounts for roughly 6% of sore throat cases, based on a meta-analysis published in the Annals of Family Medicine. That number holds fairly steady across age groups, though some studies in college-age populations have found prevalence as high as 25%. For comparison, Group A strep causes about 20 to 30% of sore throats in children and 5 to 15% in adults, making strep C a less frequent but far from rare cause of pharyngitis.
Symptoms and Severity
Strep C infections produce a clinical picture that closely resembles Group A strep. The hallmark is a painful sore throat with redness and swelling, often accompanied by fever, swollen lymph nodes in the neck, and sometimes white patches on the tonsils. Because the symptoms overlap so heavily, you can’t distinguish between the two based on how you feel alone.
Most strep C throat infections are mild and resolve with antibiotics. However, strep C can occasionally cause more serious problems, including skin and soft tissue infections, septic arthritis, bone infections, pneumonia, and bloodstream infections. Post-infectious complications like kidney inflammation (glomerulonephritis) have been documented, particularly in outbreaks linked to contaminated dairy. Rheumatic heart disease from strep C has been reported but is extremely rare.
Why Standard Strep Tests Can Miss It
The rapid strep test your doctor uses in the office is designed to detect Group A strep only. It will not pick up Group C. This means you could have a strep C infection, test negative on the rapid test, and be sent home without antibiotics. A throat culture can grow Group C bacteria, but many clinics don’t specifically look for it unless the rapid test is negative and symptoms are persistent. PCR testing offers the most reliable detection, with higher sensitivity than either cultures or antigen tests, though it’s not available everywhere.
If you have classic strep throat symptoms but your rapid test comes back negative, it’s worth asking whether a culture or PCR test could identify non-Group A strep as the cause.
Treatment
Strep C responds to the same antibiotics used for Group A strep. Penicillin and amoxicillin are the standard first-line options, typically prescribed for 10 days. Most people start feeling better within two to three days, but finishing the full course matters to clear the bacteria completely and reduce the risk of complications. For people with penicillin allergies, alternative antibiotics are available.
Once you’ve been on antibiotics for 12 hours, you’re generally considered no longer contagious and can return to work, school, or normal activities as long as you feel well enough.