CHENNAI: Up to nine people can get infected while travelling on a half-full city bus with one Covid-19 positive passenger, shows a study by scientists at the Anna University and Puducherry-based ICMRVector Control Research Centre. The numbers can increase if there are more infected patients or if the bus is more crowded or if the passengers travel longer distances. In the study, recently published in peer-reviewed scientific journal VirusDisease (formerly known as ‘Indian Journal of Virology), scientists used the 21-G Tambaram to Broadway bus route to simulate the Covid-19 infection scenario.
They assumed that five passengers board or leave the bus at each of the 40 stops on the 36.1km route. There would be 20 passengers at all times. “We assumed at least one of the passengers was SARS-CoV-2 infected at the initial point,” said the study’s first author Ganesh Ram Arumugam, assistant professor in the department of instrumentation engineering at Anna University. The mathematical model allows infected individuals to enter and exit the bus at subsequent bus stops randomly. The aim was to estimate the number of secondary infections on one of the longest bus routes during a pandemic.
The reproductive number (R0) — an epidemiological metric used to measure the transmissibility of infectious agents — was estimated taking into consideration duration of travel, time at each bus stop, total infection, the total number of passengers, and volume of breathing space inside the bus. “The reproduction number increases progressively over the duration of the trip for a single index case and is higher at the bus stops after the entry of the additional primary cases.
At the end of the journey, the R0 reaches a value of 1.04,” said co-author Kamalanand Krishnamurthy, assistant professor in the department of instrumentation engineering at Anna University The number of secondary infections for each trip from Tambaram to Broadway varies from five to nine for each trip, depending on the number of people on the bus, he said. “People must wear masks and maintain social distance to reduce the risk of infection,” he said. The highest number of secondary infections was observed at the destination terminus due to the prolonged exposure, he said. The study also picked up the potential locations (bus stops) for higher secondary infections due to the local population density, the corresponding author Lourduraj De Britto from the ICMR- Vector Control Research Centre wrote.
They assumed that five passengers board or leave the bus at each of the 40 stops on the 36.1km route. There would be 20 passengers at all times. “We assumed at least one of the passengers was SARS-CoV-2 infected at the initial point,” said the study’s first author Ganesh Ram Arumugam, assistant professor in the department of instrumentation engineering at Anna University. The mathematical model allows infected individuals to enter and exit the bus at subsequent bus stops randomly. The aim was to estimate the number of secondary infections on one of the longest bus routes during a pandemic.
The reproductive number (R0) — an epidemiological metric used to measure the transmissibility of infectious agents — was estimated taking into consideration duration of travel, time at each bus stop, total infection, the total number of passengers, and volume of breathing space inside the bus. “The reproduction number increases progressively over the duration of the trip for a single index case and is higher at the bus stops after the entry of the additional primary cases.
At the end of the journey, the R0 reaches a value of 1.04,” said co-author Kamalanand Krishnamurthy, assistant professor in the department of instrumentation engineering at Anna University The number of secondary infections for each trip from Tambaram to Broadway varies from five to nine for each trip, depending on the number of people on the bus, he said. “People must wear masks and maintain social distance to reduce the risk of infection,” he said. The highest number of secondary infections was observed at the destination terminus due to the prolonged exposure, he said. The study also picked up the potential locations (bus stops) for higher secondary infections due to the local population density, the corresponding author Lourduraj De Britto from the ICMR- Vector Control Research Centre wrote.
