Study affirms need for widespread testing
Testing per million
National average
Rank among states and UT based on tests per million
THE FINDINGS SUGGEST THAT FOR EVERY PERSON VISIBLY SICK AND SPREADING THE SYMPTOM, THERE WILL BE MORE THAN ONE WHO SILENT SPREADER
NEW DELHI: People who show no symptoms of a Covid-19 illness are likely to have comparable levels of the virus in their body as those who exhibit signs of the disease such as fever and cough, according to a new peer-reviewed study of the outbreak in a small town Italian town that recorded the country’s first death.
The findings reaffirm the need for indiscriminate testing of people and widespread use of facecovering objects such as masks, especially in a country like India where detection of silent spreaders could prove to be difficult due to high population density.
The study covered most of the 3,200 people in the town of Vò who were tested for infection at the start of a 14-day lockdown and after two weeks. “Notably, 42.5% (95% CI 31.5-54.6%) of the confirmed infections detected across the two surveys were asymptomatic (i.e. did not have symptoms at the time of swab testing and did not develop symptoms afterwards)... We found no statistically significant difference in the viral load of symptomatic versus asymptomatic,” the report by researchers from University of Padua and Imperial College London said. Italy was one of the first Western nations to be prominently hit by the pandemic, with close to 15% of all infected people succumbing to the viral illness. The fatality ratio is close thrice the global average.
While viral load does not exactly reflect how infectious a person is, it largely is believed to be a contributor to “viral shedding.” The findings suggest that for every person visibly sick and spreading the symptom, there will be more than one who might be spreading it silently.
“The result on asymptomatic carriers is key… This tells us that if we find a certain number of symptomatic people testing positive, we expect the same number of asymptomatic carriers that are much more difficult to identify and isolate,” said one of the authors, Enrico Lavezzo, from the department of molecular medicine of the University of Padua, in an email to HT.
“On the one hand, it is likely that a symptomatic infection transmits large quantities of virus, e.g. via coughing, it is also reasonable to think that symptoms may induce a symptomatic infection to stay at home thus limiting the number of contacts and hence the transmission potential,” Lavezzo said, adding that asymptomatic people are then more likely to fuel an outbreak if they carry on with their activities as usual.
This makes widespread testing crucial. “Our research shows that testing of all citizens, whether or not they have symptoms, provides a way to manage the spread of disease and prevent outbreaks getting out of hand,” said co-lead researcher Andrea Crisanti, who holds positions in University of Padua as well as the Imperial College.
In India, all close contacts of a confirmed infected person are eligible for a test, but people with no symptoms and who cannot establish they were in close contact with a confirmed patient are eligible -- a decision that takes into account the limited availability of test.
India has made covering the face mandatory for people and Prime Minister Narendra Modi urged citizens to follow this rule during a televised address on Tuesday.
The study also showed that a lockdown drastically cut transmission rates, which meant that, “despite silent and widespread transmission, the disease can be controlled,” Crisanti added.