New Delhi, May 25
Maintaining social distance of two metres is not enough as coronavirus, that spreads via aerosol, can be carried up to 10 metres through the air, experts warned on Tuesday, adding that double masks, coupled with hand hygiene and proper ventilation could be the key to curb the spread.
Coronavirus was earlier deemed to be spread via droplets. But a new assessment published in the medical journal The Lancet last month revealed that there is consistent, and strong evidence to prove that the SARS-CoV-2 virus, which causes Covid-19, is predominantly transmitted through the air.
On the other hand, evidence supporting large droplet transmission was almost non-existent. Earlier this month, the US Centers for Disease Control and Prevention (CDC) said that coronavirus is airborne.
The Indian government also, in a recent advisory, said that aerosols can travel up to 10 metres from the infected person, and that aerosols, through the infected person, can fall within two metres but can be carried up to 10 metres through the air.
"Obviously, a distance of two metres is not enough. That the virus is aerosol-borne probably explains why the disease is spreading more rapidly. What we must stress more on is Covid-appropriate behaviour," HS Chhabra, Medical Director of Indian Spinal Injuries Centre, told IANS.
"The virus can sustain in the air for six hours and it can travel 10 metres of distance. One should wear double masks and when someone is wearing double masks, then two metres distance is enough," added Vikas Maurya, Director and HOD, Pulmonology, Fortis Hospital, Shalimar Bagh.
The Union government's Principal Scientific Advisor, Prof K Vijay Raghavan, recently released an advisory "Stop the Transmission, Crush the Pandemic - Masks, distance, sanitation and ventilation, to prevent the spread of SARS-CoV-2 virus", which highlights the important role well-ventilated spaces play in diluting the viral load of infected air in poorly-ventilated houses, offices etc.
Ventilation can decrease the risk of transmission from one infected person to the other.
The advisory reads that just as smells can be diluted from the air through opening windows and doors and using exhaust systems, ventilating spaces with improved directional air flow decreases the accumulated viral load in the air, reducing the risk of transmission.
As people have become over-dependent on ACs, 90 per cent of the air is recirculated within the building and only 5 per cent fresh air is brought in most modern buildings.
"This increases the risk of cross-infection significantly as we now know that the coronavirus can be transmitted through aerosols. Where possible in hospitals, windows must be opened on opposite walls to allow for cross ventilation and natural air exchange," Rahul Kadri, Partner and Principal Architect at Mumbai-based IMK Architects, told IANS.
"In sterile zones, air conditioning systems will need to be upgraded to incorporate a three-stage filtration process with UV treatment in the AHU (Air Handling Unit) or ducts in order to dilute and remove contaminated indoor air," he said.
If an area is well-ventilated, then there is nothing much to worry but when an area is not properly ventilated, people need to maintain proper distance and wear masks, the experts said. But for people living in congested areas, maintaining distance or ventilation is a hard task.
Experts suggested that people living in smaller houses and congested areas must wear masks all the time, even when at home to avoid the spread and for ventilation, they must use air outlets or exhaust fans.
Public transport, offices and malls with no ventilation poses a big risk when it comes to infection spread.
"Introducing exhaust systems to improve air flow in AC buses and metros, putting HEPA filters in AC systems wherever possible and cleaning and replacing them regularly is important. In malls and big offices, systems like roof ventilators and HEPA filters can help," Chhabra said.
"It is a massive exercise but that is the answer if the virus is aerosol-borne in which case it remains suspended in the air for quite a long time -- as long as 3-4 hours," he noted.
Along with double masks, hand hygiene, people must frequently clean high contact points like door handles, switches, tables, chairs, etc, regularly disinfect floors, keep doors and windows ajar even while the AC is on, health experts emphasised.
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