Since March 2 when the second wave of coronavirus disease (Covid-19) cases was reported in Delhi and Hyderabad, India has not reported any case of community transmission, but the government is working to control cases of focal outbreaks in some states.
Almost a dozen technical teams from the Centre have been sent to places such as Agra, Jaipur, Pune, Delhi and Bhilwara in past one month to contain localised focal outbreaks.
Focal outbreaks or local clustering of positive cases usually occur when family members, neighbours, friends or colleagues acquire infection from an "imported case", where a person who gets infected abroad but tests positive after arriving in India.
"The local clustering of cases was reported from places such as Agra (Uttar Pradesh), Jaipur and Bhilwara (Rajasthan); we managed to contain both Agra and Jaipur, and Bhilwara is in the phase of containment. We can't call it community transmission because through successful contact tracing our teams managed to pinpoint the source of infection, the index patient who had a travel history or history of having come in contact with an infected person," said a senior scientist involved in Covid-19 containment who spoke on condition of anonymity.
"We are also investigating Maharashtra and Kerala (for such cluster transmission) as numbers are increasing in these two states; it could also be clustering or probably purely travel-related. As soon as clustering was established, we quickly implemented containment strategies, and it worked," the scientist added.
How does the cluster containment strategy work? The Union health ministry has a "Micro Plan for Containing Local Transmission of Coronavirus Disease (COVID-19)" in a defined geographic area. This involves a focal area and then a buffer area surrounding it where containment measures are put in place.
As of now, the government has not begun door-to-door testing to contain the infection, and has largely relied on the Kerala model wherein everyone within a 3km radius (focal area) of a positive case, and buffer area (5km) are screened for symptoms in cases where clustering has been established.
"We do random testing in the cluster and testing of all high-risk personnel and pneumonia patients in the area to check for the extent of transmission. Those who show symptoms are usually placed under isolation as suspected cases. This helps break the chain of transmission. Once the transmission link is broken, the localised outbreak is contained," the scientist said.
Pneumonia patients are closely monitored as pneumonia is one of the conditions that severely ill Covid-19 positive patients develop.
"Door-to-door testing in a country of 1.3 billion people is not feasible. However, to contain local outbreak of Zika in Jaipur in 2018, random testing was done in the areas from where clustering was reported to contain the spread," said Dr Nivedita Gupta, a senior scientist with the Indian Council of Medical Research during one of council's briefings.
A Lancet paper published last week on investigation of three clusters of Covid-19 in Singapore showed that 36 Covid-19 cases were linked epidemiologically to the first three clusters of circumscribed local transmission. Direct or prolonged close contact was reported in affected individuals, among 425 people who were quarantined. The median incubation period of SARS-CoV-2 was four days. It did not exclude indirect transmission.
The paper added: "SARS-CoV-2 is transmissible in community settings, and local clusters of Covid-19 are expected in countries with high travel volume from China before the lockdown of Wuhan and institution of travel restrictions. Enhanced surveillance and contact tracing is essential to minimise the risk of widespread transmission in the community."
National Centre for Disease Control (NCDC) is also keeping an eye open for cases of Covid-19 as a part of its large-scale surveillance under the integrated disease surveillance programme.
"ICMR does sample surveillance and our surveillance is on a larger scale, based on clinical signs and symptoms, as our teams are trained to pick up signs of clustering of fever cases in community. Our disease surveillance network is for 33 diseases, including Nipah, Ebola, H1N1, and Covid-19 is now a part of it; the network reaches even the village level through adequately trained ASHA and anganwadi workers," said Dr Sujeet K Singh, director, NCDC.
Close to 2 lakh people are under community surveillance as part of IDSP's contact tracing efforts, according to data released by the Union health ministry on Tuesday.
Experts say country's IDSP units have wider reach and can be utilised for community surveillance. "IDSP is a very old programme and it has grassroot level reach. We can get very accurate data up to village level. Since in a hugely populated, and resource constrained country like India, it is not possible to test everyone, quarantine is the best option," says Dr Jugal Kishore, head, community medicine, Safdarjung Hospital.
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