GUWAHATI, March 25 - With over 30,000 people returning to their homes in Assam from various places in the last three days, the State � which has so far not reported any positive case � is on its toes, hoping that the virus does not spread here as well.
As the Prime Minister announced a 21-day lockdown from last night, many here are wondering why the government went for a three-week shutdown instead of 14 days.
Experts, keeping in view the global experiences of countries which have been successful in containing the spread of COVID-19 unlike some others where thousands of people died, have recommended that effective measures for social distancing should be taken to contain the spread of this pandemic.
While the World Health Organization (WHO) estimates the incubation period of COVID-19 could be up to 14 days, this upper limit was actually observed for a small proportion of cases of SARS (severe acute respiratory syndrome). In the context of an accelerating COVID-19 epidemic and growing uncertainty, a higher upper limit � possibly 21 days � for the incubation period (the period between exposure to an infection and the appearance of the first symptoms) seems reasonable and warranted in the interest of adequately protecting the public, they feel.
According to internal medicine and critical care consultant Dr Raj Dutta, a latest Chinese study found that a full range of incubation periods of the COVID-19 cases ranged from zero to 33 days among 2015 cases.
There were six (0.13 per cent) symptom-free cases, including four females with a median age of 25.5 years and two males with a median age of 36 years. The median incubation period of both male and female adults was similar (7-day) but significantly shorter than that (9-day) of child cases. This cohort contained four transmission generations, and incubation periods of the cases between generations were not significantly different, suggesting that the virus has not been rapidly adapted to human beings.
�Interestingly, incubation periods of 233 cases (11.6 per cent) were longer than the WHO-established quarantine period (14 days). Data modelling suggested that if adults take an extra four-day or seven-day of isolation (a quarantine period of 18 or 21 days), 96.2 per cent or 98.3 per cent, respectively, of the people who are developing symptoms will be more effectively quarantined,� Dr Dutta explained referring to the study.
Patients transmitted via lunch or dinner parties (i.e., gastrointestinal tract infection through oral transmission) had a significantly longer incubation period (9-day) than other adults transmitted via respiratory droplets or contaminated surfaces and objects.
Experts say quarantine measures separate and restrict the movement of people who were exposed to a contagious disease, so as to provide appropriate care if they become ill, and to protect the public from infection. Discharging someone from quarantine before the end of the actual incubation period of the disease can prove disastrous, if that person subsequently develops the disease while not contained.
�We must get the upper limit of the incubation period right, or we could defeat the purpose of quarantining,� they said.