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"Blatant violations of Covid norms have been observed in several parts of the country, especially in public transport and at hill stations..." the letter said, "Consequently, increase in 'R' factor in some states is a matter of concern. 'R' factor above 1.0 is an indicator of (high) spread of COVID-19."
"... authorities concerned be made responsible for ensuring Covid-appropriate behaviour in all crowded places, such as shops, malls, markets, restaurants and bars, bus stations, railway platforms/stations, banquet halls/marriage halls, stadia/sports complexes (if opened up) ... as well as all other areas identified as hotspots for transmission of COVID-19," the Home Ministry said.
"It is emphasised that the second wave of Covid is not over. We ought to remember that while the reach of vaccination is increasing considerably, there is no room for complacency..." the ministry added.
The letter comes a day after Prime Minister Narendra Modi warned the country that continued laxity in adhering to the rules - which include wearing face masks and maintaining social distancing in public spaces - could invite a potentially disastrous third wave of infections.
The Prime Minister's warning came after images from hill stations and city markets - of thousands of people without masks and zero social distancing - were circulated on social media, drawing severe criticism from medical experts and the Health Ministry.
"... today I will say emphatically that it is not okay to have huge crowds in hill stations and markets without masks. The virus does not come and go on its own... we bring it with us when we disobey the rules. Experts are warning us repeatedly that careless behaviour - like overcrowding - will lead to an increase in Covid cases," he said.
The Home Ministry reiterated that warning: "You would appreciate that we must guard ourselves against complacency and laxity, which creep in as positivity declines. Instead, during period of low positivity, efforts must be stepped up to prevent any future surge."
The 'R' factor is a measure of how many people are being infected by one infected person. An 'R' of 1 means one person will, on average, infect one other person. In a pandemic situation the 'R' target is less than 1.0, which ensures the virus will eventually stop spreading because it cannot infect enough people to sustain the outbreak.
This morning the 'R' value was 0.95 - up from .89 a week ago and .74 four weeks ago. At the peak of the second wave - when over four lakh new cases were reported daily - the 'R' value was 1.32 - the highest since April 2020.
A recent study by scientists from Chennai's Institute of Mathematical Sciences says increasing 'R' values means a falling national active caseload - this morning it was around 4.29 lakh - the lowest since March 25 - must be viewed with caution. "Even a .1 change can make a big difference..." the lead researcher on the study said.