Strep throat is highly contagious. It is caused by the bacteria Streptococcus pyogenes (group A strep) and spreads primarily through respiratory droplets when an infected person talks, coughs, or sneezes. It can also spread via direct contact with infected sores or by touching surfaces contaminated with these droplets and then touching the nose or mouth
. People can begin spreading the bacteria during the incubation period, which is typically 2 to 5 days after exposure, even before symptoms appear
. Those who show symptoms are generally more contagious than asymptomatic carriers, though asymptomatic individuals can still spread the infection
. Without antibiotic treatment, an infected person can remain contagious for up to two to three weeks. However, once antibiotics are started, contagiousness usually decreases significantly within 24 to 48 hours, making it safer to return to normal activities after this period
. Summary of contagiousness:
- Mode of spread: Respiratory droplets, direct contact, contaminated surfaces
- Incubation period: 2–5 days (contagious even before symptoms)
- Contagious period untreated: Up to 2–3 weeks
- Contagious period with antibiotics: Usually less than 24–48 hours after starting treatment
Preventive measures include good hand hygiene, covering coughs and sneezes, avoiding sharing utensils, and staying home until at least 24 hours after starting antibiotics
. This high contagiousness explains why strep throat spreads quickly in close- contact settings such as households, schools, and daycare centers, especially among children
