Symptomatic patients have a greater propensity for transmission: Experts

According to the experts’ analysis, spread in large clusters was also primarily through symptomatic people.

According to the experts’ analysis, spread in large clusters was also primarily through symptomatic people.  

‘They throw out higher viral particles through cough and sneeze, spreading the infection to more people’

An analysis of 3,404 positive patients between March 9 and June 1 in the State has shown that while both symptomatic and asymptomatic people transmit the infection, the former have greater propensity for transmission.

The spread of the infection is high in clusters where symptomatic patients are the source patients, revealed the analysis taken up by a group of experts led by V. Ravi, Head of Neuro-Virology at NIMHANS and part of the State’s COVID-19 expert committee.

“Symptomatic patients can spread the infection to a large number of people because when they cough and sneeze they throw out higher viral particles. In comparison, the infection spread through asymptomatic patients is limited to smaller numbers as they do not cough and sneeze,” Dr. Ravi told The Hindu.

From the 3,404 patients, the expert group has completed contact tracing and source analysis for 966 patients. “In these, we found that 144 were source cases who had spread the infection to an additional 822 people. Of the 144, 90 were symptomatic patients and 54 asymptomatic. On further analysis, it was found that the 90 symptomatic patients gave the infection to 645 people and 54 asymptomatic patients to 177 persons,” explained Dr. Ravi. “On an average, each symptomatic patient has spread the infection to 7.1 individuals as against every asymptomatic patient who spread the infection to 3.2 individuals,” he said.

Spread in large clusters was also primarily through symptomatic people. “For instance, the source patients in the Jubiliant pharma company cluster in Nanjangud and the Chandini Chowk cluster in Shivajinagar of Bengaluru were symptomatic. Hence, it is very important to track symptomatic patients,” Dr. Ravi said.

The Jubiliant pharma cluster was the largest cluster in the State, wherein 74 persons had contracted the infection through the source case patient no. 52. However, it still remains a mystery on how P-52 got infected.

In Shivajinagar, where 47 persons have been infected, the source was patient no. 653, a housekeeper at a quarantine hotel in the area, who transmitted the virus to a nurse from Shifa Hospital from whom the cluster developed.

“Whenever a symptomatic patient spreads the infection, the percentage of symptomatic cases among the total infected is high. However, when asymptomatic patients spread the infection, it is more likely that the infected person will also be asymptomatic,” Dr. Ravi said, quoting the analysis.

Early detection

With the analysis revealing that the pandemic seems to be primarily driven by symptomatic cases in Karnataka till June, Dr. Ravi is of the opinion that people with mild symptoms, if detected early and admitted to hospitals and treated, can avert death.

It can be recalled that a position statement by the National Centre for Infectious Diseases and the Chapter of Infectious Disease Physicians, Academy of Medicine, Singapore, had also stated that transmissibility through asymptomatic cases is low.

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Printable version | Jul 8, 2020 7:01:18 AM | https://www.thehindu.com/news/national/karnataka/symptomatic-patients-have-a-greater-propensity-for-transmission-experts/article31957572.ece

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