In a journal recently a research paper is published named “Serial Interval of SARS-CoV-2 was Shortened Over Time by Non-pharmaceutical Interventions”. According to it, China was able to contain COVID-19 because of its ability to manage the serial interval.
Since the outbreak of COVID-19, almost every time we listen or read about new terms related to the pandemic and now it becomes common. Benjamin Cowling and other researchers at the University of Hong Kong written the research paper that has been published in the Journal Science.
About Serial Interval
Serial interval is the period between symptom onset of a primary case and symptom onset of secondary cases (contacts) that are generated by the primary case. Or we can say that the serial interval is the gap or duration between the onset of COVID-19 symptoms in Person X and Person Y, who is infected by Person X.
Origin of Serial interval term
It was first used by the British physician William Pickles, who had at the beginning referred to it as transmission interval with reference to hepatitis epidemic in the UK during 1942-45.
After some time or later, RE. Hope Simpson a British physician used the term serial interval. He defined the term as the interval between the successive illness onsets.
Explanation provided by the researchers in their paper titled “Serial interval of SARS-CoV-2 was shortened over time by non-pharmaceutical interventions”.
They explained that the dependency of serial interval is on other epidemiological parameters like the incubation period and the reproduction rate or R naught.
What is the incubation period?
It is the time between exposure of a person to the virus and symptom onset.
What is Reproduction rate?
It is the number of people who will be infected by one infected person.
Changes in serial interval indicate:
The serial interval will help to gauge the effectiveness of infection control interventions apart from indicating the immunity of rising population and forecast the incidence of future.
Also, more quickly people who contracted COVID-19 are identified and isolated, the serial interval will become shorten and so, the opportunities for the transmission of virus will be cut down.
Therefore, it is necessary to manage serial interval and for that a proper system of contact tracing, quarantine and isolation protocols are followed or should be in place.
Serial interval managed by China and South Korea
– In Wuhan, China the serial interval came down from 7.8 days to 2.6 days between early January and early February. They quarantine the contacts within one day from symptom onset and this helped to reduce the transmission by 60 per cent.
– In South Korea, the serial interval was estimated to be 3.63 days.
– Both the countries put efforts for contact tracing, quarantine and isolation to ensure that the infected patients could not infect any more people later in the infection cycle.
– And the interventions were also controlled such as intra-and inter-city travel. Different forms of social distancing were also implemented on wide-scale to kept the serial interval low.