india

Updated: Mar 21, 2020 12:48 IST

It is the second week of February in south Korea. News is trickling in of an exploding coronavirus outbreak in mainland China’s Wuhan city that has affected tens of thousands of people and killed hundreds already.

But in the capital Seoul, authorities are satisfied with strict containment measures and airport controls put in place after isolating a 35-year-old Chinese woman upon landing at Incheon airport on January 20. The number of cases is relatively low, 30, and the casualties are in single digits.

Aggressive testing and tracking of infected people has helped the government keep a handle on the disease.

All that is about to change.

Unknown to authorities, a 61-year-old woman in the country’s fourth-largest city, Daegu, is attending services of a fringe Christian cult. She has a fever, but thinks it is a common cold. She will attend four congregations before getting herself tested; and testing positive for the coronavirus on February 17.

February 19, and the number of cases in south Korea has surged to 346. The woman, dubbed Patient 31, will go on to infect at least 1,160 people, upend the country’s plan of containing the deadly contagion and become a global example of a Covid-19 super spreader.

Now, a breakthrough study has called for speedily arresting such super-spreading events (SSEs) because they lead to an explosive growth in the early stages of the outbreak and contribute to sustained transmission in the later stages.

The paper, to be published in the Emerging Infectious Diseases journal of the Centre for Disease Control and Prevention in the United States, came on a day fears surged in India after Bollywood singer Kanika Kapoor, who tested positive for the coronavirus infection, was revealed to have attended social events with top politicians, forcing many leaders to go into quarantines. One of those politicians attended both Parliament and a breakfast meeting with the President.

In SSEs, one infected person passes the contagion to a large number of others, typically by attending a public event or being in a public place. Most SSEs conform to the 80:20 rule that holds 20% of the infected population typically responsible for 80% of the infections.

“Although we still have limited information on the epidemiology of this virus, there have been multiple reports of SSEs, which are associated with both explosive growth early in an outbreak and sustained transmission in later stages,” said the study’s authors, Thomas R Frieden and Christopher T Lee.

“Although SSEs appear to be difficult to predict and therefore difficult to prevent, core public health actions can prevent and reduce the number and impact of SSEs. To prevent and control of SSEs, speed is essential,” they added. The study identified five key factors in mitigating SSEs.

The first is pathogenic, which comprises understanding the transmission potential, persistence capacity and virulence of the virus. The second is host, including the duration, location and burden of the infection. The third is environmental, which includes population density and availability and use of infection prevention and control measures in healthcare facilities. The fourth is behavioral, which includes social customs, health-seeking behavior, and adherence to public health guidance. The fifth is response, which includes the timely and effective implementation of prevention and control measures within the community and in health care settings.

“SSE prevention and mitigation depends, first and foremost, on quickly recognizing and understanding these events,” the authors said, using a statistical analysis of data from Hong Kong, Vietnam, Singapore, and Canada to show that delaying the 2003 SARS control measures by just a week could have tripled the size of the epidemic that killed 774.

“Because individual superspreaders can only be identified retrospectively, universal implementation of triage procedures, rapid diagnosis and isolation, administrative controls (flow patterns and procedures for patients, visitors, and staff), and engineering controls (isolation rooms, partitions, ventilation systems) are all necessary,” the paper said.

Globally, experts have used the case of Patient 31 in south Korea to caution authorities and governments about the danger of super-spreaders.

“Countries should develop and implement protocols for implementation of rapid identification, diagnosis, and isolation of patients,” the authors said.