According to the WHO, the asymptomatic transmission is the virus transmission from a person who does not develop symptoms
The Indian Council of Medical Research (ICMR) gave two recent figures, on separate days, about people without symptoms testing positive for COVID-19. This has created fear asymptomatic coronavirus patients suddenly falling very sick and infecting other people. Dr. R R Gangakhedkar, ICMR’s head of epidemiology and infectious diseases, on April 20, said that 80% of people have the infection without symptoms. These people will be asymptomatic but if their medical tests are conducted, there is a possibility that they will be positive. He further said that only after a person is symptomatic, the RT-PCR test comes positive and people take time to be symptomatic. The next day, he clarified that in India, 69% of those who had tested COVID-19 positive are asymptomatic. The 80% people that he had mentioned the previous day is based on just one study, Gangakhedkar was quoted saying in an IE report.
As per a study from China, 44% of those who had contracted the novel Coronavirus disease had caught it from an asymptomatic person. The study estimates that the viral shedding, which is the stage when an individual infects the other person, starts happening 2-3 days before the onset of symptoms. According to the researchers, the highest viral load in throat swabs has been observed at the time of symptom onset and concluded that infectiousness peaked on or before the onset of symptoms. The researchers estimated that in secondary cases, 44% of them were infected during the presymptomatic stage of index cases. This is in settings with clustering of substantial household, finding of the active case as well as quarantine outside the home.
The three stages of COVID-19 transmission recognized by the WHO are asymptomatic stage, presymptomatic stage, and symptomatic stage. Symptomatic transmission is the transmission of the infection from a person while they are experiencing the symptoms, by direct contact with infected persons, through respiratory droplets, or by contact with contaminated objects or surfaces. In this type of transmission, the incubation period of the virus ranges from 5 to 14 days. Presymptomatic transmission is the type of transmission when a person spreads the infection before he/she develops the symptoms, but eventually, they themselves develop the symptoms.
According to the WHO, the asymptomatic transmission is the virus transmission from a person who does not develop symptoms. A few laboratory-confirmed cases have been reported that are truly asymptomatic, and so far, there has been no documented asymptomatic transmission, WHO stated. However, this does not exclude the chances that it may occur. As part of contact tracing efforts, asymptomatic cases have been reported in some countries.
According to the US Centers for Disease Control and Prevention (CDC), both types of transmission of the virus- presymptomatic and asymptomatic, are possible. The viral shedding’s onset and duration, as well as the period of infectiousness for novel Coronavirus, are not yet known. Similar to infections with MERS-CoV as well as SARS-CoV, the SARS-CoV-2 RNA may be detected in the upper respiratory tract or lower respiratory tract for weeks after the onset of the illness. Detection of viral RNA, however, does not necessarily mean that COVID-19 is present. Reports are available on asymptomatic infections and pre-symptomatic infections with SARS-CoV-2, but their role in transmission is still unknown. The CDC further stated that the incubation period of SARS-CoV-2 as well as other coronaviruses such as MERS-CoV, SARS-CoV, ranges from 2 to 14 days.
AIIMS Director and a respiratory medicine specialist, Dr. Randeep Guleria was quoted in the report saying that till the time a vaccine is found, there is no alternative to basic safety practices like hand-washing, social distancing and wearing a mask. It is believed that a person after being infected by the virus can spread the disease up to 14 days. Since it is a new disease, knowledge about it is still evolving.
Recently, a 54-year-old woman has been tested positive in Kerala, almost a month after she arrived from abroad, and ever since she had been quarantined at home. According to Health officials, so far, there have been at least a dozen cases of people testing COVID-19 positive after having been quarantined themselves for 28 days. Recently, the state of Telangana decided to increase the home quarantine period from 14 days to 28 days. From the beginning, the Union Health Ministry has also advocated that patients should be followed up for 28 days instead of 14 days.