Why do adults tend to get strep (streptococcal) throat less often than children?

Why Adults Get Strep Throat Less Frequently Than Children

Adults experience significantly lower rates of Group A streptococcal (GAS) pharyngitis compared to children due to fundamental epidemiological and immunological differences—GAS causes only 5-15% of acute pharyngitis cases in adults versus 15-35% in children. 1

Primary Epidemiological Factors

Age-Related Incidence Patterns

• School-age children (5-15 years) represent the peak demographic for GAS pharyngitis, with prevalence rates substantially higher than any other age group 1
• Adults aged 15-44 years have GAS carriage rates of only 2.3%, compared to 10.9% in children aged 14 years or less 1
• In adults over 45 years, asymptomatic carriage drops even further to 0.6% 1

Exposure and Transmission Dynamics

• Adults with higher occupational or household exposure to children face increased risk—specifically parents of school-age children and those working closely with children have rates approaching pediatric levels 1
• In family studies, when school-age children develop GAS pharyngitis, 43% of families experience at least one secondary case, with adults being equally susceptible when exposed 2
• The primary reservoir for GAS transmission remains school-age children, where 15-20% may be asymptomatic carriers during winter and spring months 1

Immunological Considerations

Acquired Immunity Through Repeated Exposure

• Development of acute rheumatic fever (ARF) requires repeated GAS exposures or immune system priming, which explains why ARF is extremely rare in adults even with untreated streptococcal pharyngitis 1
• Children under 3 years also show low rates of GAS pharyngitis and ARF, suggesting that multiple exposures over time are necessary to develop the immune response patterns seen in school-age children 1
• Adults have typically accumulated immunity from childhood exposures, reducing both infection rates and complication risks 1

Clinical Implications of Lower Adult Prevalence

Diagnostic Approach Differences

• The low prevalence of GAS in adults (5-15%) versus children (15-35%) fundamentally changes the diagnostic strategy, with some guidelines suggesting that negative rapid antigen detection tests (RADT) in adults do not require confirmatory throat culture 1
• This contrasts sharply with pediatric recommendations where negative RADTs should be confirmed by throat culture due to higher pretest probability 1
• The extremely low risk of ARF in adults—even with undiagnosed and untreated GAS pharyngitis—further justifies less aggressive diagnostic approaches 1

Treatment Considerations

• Despite lower infection rates, adults who do develop GAS pharyngitis present with similar clinical features to children and benefit equally from antibiotic therapy when infection is confirmed 2
• However, the number needed to treat for symptom reduction is 6 after 3 days and 21 after 1 week, representing modest benefit regardless of age 1

Common Pitfalls to Avoid

• Do not assume all adult sore throats are viral—approximately 24% of adults presenting with pharyngitis may have GAS infection, particularly younger adults and those with household exposure to children 3, 2
• Avoid empiric antibiotic treatment without testing, as over 60% of adults with sore throat receive unnecessary antibiotics despite the low prevalence of bacterial infection 1
• Remember that adults with confirmed GAS pharyngitis have similar secondary transmission rates within families as children, making appropriate diagnosis and treatment important for outbreak control 2