An alarming rise in asymptomatic persons — they do not show noticeable symptoms like illness, but can still pass the Coronavirus to others — turning out to be Covid-19 positive is the next big concern for the Government, already grappling with an ever-increasing tally of cases of the deadly pathogen in India.
On Sunday, the positive cases crossed the 16,000-mark while the toll was nearly 550 across the States.
With 186 asymptomatic cases, Delhi joined the list of States like Karnataka, where 60 per cent of the total 315 cases are asymptomatic ones. In worst-affected Maharashtra, the trend is more worrisome and alarming as over 70 per cent of novel coronavirus cases in the State are asymptomatic with patients having no knowledge that they were infected.
Various studies using the mathematical modelling of outbreaks in Tianjin, China, and Singapore in January and February have also found significant amounts of spread by people who had not shown or developed Covid-19 symptoms.
The asymptomatic cases came to the fore only after India started aggressive testing of all foreign-returned and those with travel history to Covid-19-incidence regions of the country. Some even tested positive way after completing the 14-day period.
A district-wise analysis of data in Karnataka up to April 16 shows 186 of the 315 Covid-19 patients to be asymptomatic patients.
Experts say that this trend will add additional stress on the state machinery, which is already struggling to cope with the increasing samples it has to test daily.
“If there are more asymptomatic cases than those patients with symptoms, the authorities will not be able to neglect a large section of the population, which means an added burden on testing labs,” one of them said. An asymptomatic person does not show noticeable symptoms like illness, but can still pass the virus to others.
According to researchers, with a very high viral load in their upper respiratory tract, such persons can shed the virus through spitting, touching their mouths or noses and then a surface, or possibly talking. People who don't feel ill end up coughing or sneezing occasionally.
“We are actually dealing with a very huge challenge along with the rest of the world. In this particular infectious disease, not only people who are symptomatic, but even asymptomatic persons as a carrier may pass on the infection,” Lav Agarwal, Joint Secretary, Union Health Ministry had said a few days ago.
If the asymptomatic cases are not tracked down early and subjected to the preventive and therapeutic interventions, the country might witness rapid spurt in the cases.
Maharashtra Chief Minister Uddhav Thackeray too cautioned that over 70 per cent of novel coronavirus cases reported in the state were asymptomatic and the patients did not know that they were infected. "70 to 75 percent positive cases are asymptomatic. At least 52 per cent of the patients are in serious conditions. Many have reported in the last stage. I want to appeal that do not hide symptoms," Thackeray said.
Similarly, in Tamil Nadu, which is the third worst-hit State many patients who have tested positive for COVID-19 , were asymptomatic. So far, 15 COVID-19 positive patients have died in Tamil Nadu while in Odisha, asymptomatic cases and discovery of coronavirus infection in persons even after the 14-day quarantine or isolation period has added to the trouble of the Government, underlining an urgent need to redefine efforts for containing spread of COVID-19 in the State.
While asymptomatic cases constitute almost the bulk of COVID-19 cases in the State, the pattern has led to serious concerns over their ability to spread the virus in the community without knowledge of themselves or their contacts.
Health experts have called for aggressive testing apart from carrying out strict containment measures at places where cluster of positive cases has emerged.
In an article in the New England Journal of Medicine, Bill Gates, co-chair of the Bill and Melinda Gates Foundation, expressed concern about the spread of the disease by people who haven't yet developed symptoms, or who are only a bit sick.
"There is also strong evidence that it can be transmitted by people who are just mildly ill or even presymptomatic. That means COVID-19 will be much harder to contain than the Middle East respiratory syndrome or severe acute respiratory syndrome (SARS), which were spread much less efficiently and only by symptomatic people," he said.
Others agree that people without serious symptoms play a substantial role in the spread of the new coronavirus.
"Asymptomatic and mildly symptomatic transmission are a major factor in transmission for Covid-19," said Dr. William Schaffner, a professor at Vanderbilt University School of Medicine.
Also, large-scale studies using mathematical modelling of outbreaks in Tianjin, China, and Singapore in January and February have found significant amounts of spread by people who had not yet developed symptoms.
The study shows that between 48% and 66% of the 91 people in the Singapore cluster contracted the infection from someone who was pre-symptomatic. Of the 135 people in the Tianjin cluster, between 62% and 77% caught it from someone who was pre-symptomatic.