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Coronavirus transmission by asymptomatic patients is rare, says WHO

Delhi government says a total of 2,207 security guards have been deployed in the hospitals run by them, these include female security guards as well as those who are posted in sensitive areas. Photo: Ramesh Pathania/MintPremium
Delhi government says a total of 2,207 security guards have been deployed in the hospitals run by them, these include female security guards as well as those who are posted in sensitive areas. Photo: Ramesh Pathania/Mint

  • the available evidence from contact tracing reported by member states suggests that asymptomatically-infected individuals are much less likely to transmit the virus than those who develop symptoms

NEW DELHI: It is rare that asymptomatic covid-19 positive patients can spread the virus to their contacts, the World Health Organization (WHO) said on Tuesday.

The apex global health agency, in its interim guidance on use of masks, indicated that comprehensive studies on transmission from asymptomatic individuals are difficult to conduct, but the available evidence from contact tracing reported by member states suggests that asymptomatically-infected individuals are much “less likely" to transmit the virus than those who develop symptoms.

"From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual," Maria Van Kerkhove, infectious disease epidemiologist and the technical lead on covid-19, WHO, said in a press conference in Geneva on Monday.

Despite several studies from across the world that asymptomatic covid-19 patients are a major threat in containment efforts of the disease, Kerkhove said based on data from countries there are very few cases of spread. “We are constantly looking at this data and we are trying to get more information from countries to truly answer this question," Kerkhove said, adding it still appears to be “rare that asymptomatic individuals actually transmit onward".

Kerkhove also said in a tweet on Tuesday, “In these data, it is impt to breakdown truly asymptomatic vs pre-symptomatic vs mildly symptomatic also to note that the percentage reported or estimated to be "asymptomatic" is not the same as the percentage that are asymptomatic that actually transmit."

A study published in the Annals of Internal Medicine last week said asymptomatic persons seem to account for approximately 40% to 45% of SARS-CoV-2 infections, and they can transmit the virus to others for an extended period, perhaps longer than 14 days. The researchers warned that the virus might have greater potential than previously estimated to spread silently and deeply through human populations.

“It has been suspected that infected persons who remain asymptomatic play a significant role in the ongoing pandemic, but their relative number and effect have been uncertain," the study said.

Public health experts have questioned the WHO's statement and said it is undermining the spread of the highly infectious disease.

“As asymptomatic transmissions are difficult to pick up, surveillance data must underestimate silent transmission. Respiratory symptoms are common WITHOUT Covid-19, retrospective asking of symptoms must also under-estimate the percentage of Covid-19 without symptoms," tweeted, Chi C Leung, chairman, Advisory Committee of Hong Kong Medical Association and editor-in-chief, International Journal of Tuberculosis and Lung Disease.

The health ministry in India last month decided to revise patient discharge policy on the basis of a similar evidence even though it maintained that over 70% of the positive cases are asymptomatic in India. Lav Agarwal, joint secretary at the health ministry had said, “The new discharge policy is based on evidence where we have found that presymptomatic, mild symptomatic cases, or moderate cases for that matter not having fever for 10 days will not be able to spread the infection to others."

However, the government has directed patients not to move around after leaving the covid facility and should self-quarantine himself/herself for at least seven days and also must take all necessary precautions.


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