Explained: What is serial interval, and how can it be managed to control Covid-19?

News: According to a study, China which has now gone over a month without any locally transmitted Covid-19 cases was able to contain Covid-19 due to its ability to manage the serial interval.


  • Serial Interval: It is the duration between symptom onset of a primary case and symptom onset of secondary cases(contacts) generated by the primary case. 
    • In simple terms, the serial interval is the gap between the onset of Covid-19 symptoms in Person A and Person B who is infected by Person A.
  • Origin: The term was first used by British physician William Pickles, who had initially referred to it as transmission interval with reference to a hepatitis epidemic in the United Kingdom during 1942-45.
  • Factors on which Serial Interval depends:
    • Incubation period: It is the time between a person’s exposure to the virus and symptom onset.
    • Reproduction rate or R naught: It is the number of people who will be infected by one infected person.
  • Significance: The serial interval helps to gauge the effectiveness of infection control interventions besides indicating rising population immunity and forecast future incidence.