How Strep Throat is Transmitted
Strep throat spreads primarily through respiratory droplets when infected individuals cough or sneeze, with transmission occurring mainly during close contact with symptomatic patients. 1
Primary Transmission Routes
Respiratory Droplet Transmission
- Group A streptococcus (GAS) is transmitted predominantly through respiratory droplets released when infected persons cough or sneeze, traveling a few feet through the air before settling. 2, 1
- This droplet transmission requires relatively close contact with symptomatic individuals to pose significant infection risk. 1
- The bacteria can also spread through direct contact with infected respiratory secretions. 1
Contact Transmission
- Contaminated hands are the predominant mode of transmission for most respiratory pathogens, including strep throat. 2
- Indirect contact transmission occurs when the infectious agent transfers through contaminated intermediate objects such as door handles, countertops, or other fomites. 2
- While streptococci can survive in dust and on surfaces, environmental fomite transmission is not the primary route and accounts for less than 10% of cases in outbreak investigations. 1
Contagiousness by Patient Type
Symptomatic Patients (Highest Risk)
- Patients with acute streptococcal pharyngitis are the most contagious, actively shedding bacteria through respiratory secretions. 1
- These symptomatic individuals pose substantially higher transmission risk to close contacts compared to carriers. 1
Asymptomatic Carriers (Minimal Risk)
- Chronic carriers (less than 5% of adults) are unlikely to spread the organism to close contacts and pose very low transmission risk. 1
- During winter and spring, up to 20% of asymptomatic school-aged children may carry GAS for several months, but these carriers rarely transmit infection. 1
- Carriers have GAS present but show no immunologic response (no rising antibody titers). 1
Household and Close Contact Considerations
- Approximately 25% of household members of an index patient may harbor GAS in their upper respiratory tracts. 2
- However, routine throat cultures or treatment for asymptomatic household contacts is not necessary except in specific high-risk situations (history of rheumatic fever, outbreak settings, or frequent infections). 2, 1
- Secondary cases of severe invasive GAS infection have rarely occurred in family and institutional contacts. 2, 1
Prevention Strategies
Hand Hygiene
- Hand hygiene using alcohol-based hand rub or soap and water is the single most important method of preventing transmission of infectious agents including strep throat. 2
- Hand hygiene should be performed before and after contact with each patient or their immediate environment. 2
Respiratory Hygiene
- Respiratory hygiene and cough etiquette should be implemented as part of standard precautions to decrease transmission of respiratory tract pathogens. 2
Common Pitfalls
- Do not routinely screen or treat asymptomatic household contacts unless specific high-risk circumstances exist, as this is not cost-effective and carriers pose minimal transmission risk. 2, 1
- Recognize that environmental decontamination, while important in healthcare outbreak settings, is not the primary focus for typical community transmission prevention. 1
- Understand that the contagious period is highest during acute symptomatic illness, not during the carrier state. 1