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Cosmos Study

Strep Throat Infections Up 30% From 2017 Peak After Pandemic Drop

April 19, 2023
Dual-Team Study
Team A:Kersten Bartelt, RNAlex Piff
Team B:Christopher Alban, MDBrendan Joyce

Key Findings

  • Like other infectious illnesses, rates of strep throat infections dropped significantly in 2020, coinciding with COVID-19 pandemic precautions. Rates remained low throughout 2020 and 2021.  
  • Similar to prior to the COVID-19 pandemic, strep throat infections started to increase in September 2022. Strep throat then increased to the greatest rate of infection seen since 2017 in February 2023. 

In February 2023, the Centers for Disease Control and Prevention (CDC) noted an increase in group A Streptococcus, or strep, infections, particularly in children.1 Given this, we wanted to understand how the incidence of strep pharyngitis and strep tonsillitis (strep throat) in 2022 and 2023 compares to previous years. We identified 3.3 million strep throat infections across 982.3 million encounters from January 1, 2017, to February 28, 2023.  

From January 2017 through February 2020, strep throat infections followed a seasonal pattern, typically starting to increase in September and peaking at between 0.63 and 0.74% of encounters in February each year. Similar to other infectious respiratory illnesses like influenza and RSV, strep throat encounters dramatically decreased in March 2020, coinciding with the start of the COVID-19 pandemic. Rates remained low (less than 0.28% of encounters) but began to rise again in September 2022. As of February 2023, strep throat encounters increased to a rate nearly 30% greater than the previous peak seen in February 2017 (0.74% to 1.0% of encounters), as shown in Figure 1. 

Figure 1
Percentage of Encounters for Strep Throat
Percentage of Encounters for Strep Throat
Figure 1. Percentage of office visit and emergency encounters with a strep pharyngitis or strep tonsillitis diagnosis by month from January 2017 to February 2023. 

These findings of increased encounters for strep throat held true across all social vulnerability index (SVIs) quartiles, all U.S. census regions, and all races. Strep throat diagnoses were most common in patients ages 4-13, but all age groups followed similar trends, as shown in Figure 2. 

Figure 2
Percentage of Encounters for Strep Throat by Age
Percentage of Encounters for Strep Throat by Age
Figure 2. Percentage of office visit and emergency encounters with a strep pharyngitis or strep tonsillitis diagnosis by month from January 2017 to February 2023 stratified by age. 

These findings support the CDC’s preliminary reports of increased strep activity in 2022 and 2023, especially in children.1  

These data come from Cosmos, a HIPAA-defined Limited Data Set of more than 184 million patients from 199 Epic organizations including 1,147 hospitals and more than 24,900 clinics, serving patients in all 50 states and Lebanon. This study was completed by two teams that worked independently, each composed of a clinician and research scientists. The two teams came to similar conclusions. 

References

  1. Centers for Disease Control and Prevention. Increase in Invasive Group A Strep Infections, 2022–2023. Increase in Invasive Group A Strep Infections, 2022-2023 | CDC. Accessed on: March 14, 2023.