A recent case of a Covid-positive 25-year-old ENT postgraduate student has illustrated that close and sustained indoor proximity to Covid-19 patients will lead to infection despite masking.
Frontline medical personnel have also reiterated the point.
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The student, found positive at the Bangalore Medical College and Research Institute (BMCRI) last Tuesday, may have contracted the disease after visiting a pub on January 1 and is said to have infected a 30-year-old nurse after a 30- to 40-minute interaction in an office on-campus on Monday, sources said.
The infection happened despite the individuals involved were wearing masks. While the student wore an N-95 mask, the nurse protected herself with a triple-layered surgical mask.
“The postgraduate student did not remove her mask, but the nurse may have done so for a few minutes. This was a closed room. The two people were sitting about six feet apart,” a source said.
The student was found to be positive a day later. She is said to not have had symptoms. The nurse went on to develop a severe sore throat, along with mild fever.
Medical personnel said the nurse had developed symptoms even though she was vaccinated twice with Covishield and had also received a booster dose in the form of Covaxin.
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Dr Saptarshi Basu, Professor of Mechanical Engineering at the Indian Institute of Science (IISc), who has conducted fluid mechanics studies and efficacy of facemasks, noted that a masked person who spends time with a Covid-19 positive patient indoors faces a risk of infection, especially if confronted with Omicron.
“During the second wave, people would get sick if they ingested roughly about 100 virions of the Delta variant. With Omicron, infections can happen with the ingestion of just 20-30 virions. Masks when used in a sustained fashion indoors do not offer fool-proof protection,” Dr Basu said.
He pointed to several factors where a mask may not work — gaps around the nose left by masks in addition to improperly worn masks that expose people to gradually rising concentration of virions in aerosols circulating in indoor air.
“Closed places of any sort are a problem. Air conditioning poses particular hazards as 90% of the airflow is recycled air,” he said.
It is not yet known which variant of the virus the two positive cases were infected by.
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