Air-conditioning systems ‘could spread virus’

Covid-19 found in hospital air duct as analysis suggests disease may be more contagious than thought

CORONAVIRUS could spread around buildings via air-conditioning systems or even on a draught, analysis suggests, after scientists found traces of the virus in a hospital air duct.

The results from swab analysis of the rooms used by three coronavirus patients indicate the disease may be more contagious than previously thought.

Even though the patient in question was suffering only “mild” symptoms, scientists from the National Centre for Infectious Diseases in Singapore found evidence of the virus in the hospital’s air exhaust.

This “suggests that small virus-laden droplets may be displaced by airflows and deposited on equipment such as vents”, they said.

It comes as Sir Patrick Vallance, the Government’s chief scientific adviser, said officials were considering isolating entire households in a bid to control the outbreak, after the second death from Covid-19 in Britain.

Currently experts are warning cohabitees of people with symptoms to minimise contact and to not share a bathroom if possible, but are not advising they stay at home as well.

Published in the Journal of the American Medical Association, the new findings have implications for the safety of people using buildings which recycle internal air. The same applies to cruise ships, which typically use a mix of recycled air already inside the vessel and fresh air from outside to save on costs.

It comes after more than 700 people came down with coronavirus and at least six died on board the Diamond Princess cryuise ship.

Experts say the policy of quarantining the entire ship in Japan turned it into a “breeding ground” for Covid-19.

Another cruise liner, the Grand Princess, is currently waiting off the coast of California while tests are carried out on dozens of passengers.

Meanwhile, medics in Malta have threatened to go on strike if authorities allow in the MSC Opera, carrying 2,302 passengers, over fears of the virus.

Towards the start of the global outbreak, which has seen 3,412 deaths, virologists suspected Covid-19 required larger, heavier droplets to survive outside the body. However, the fact that it appears to survive on smaller, lighter droplets – similar to seasonal influenza – makes it more contagious.

Prof James G Dwyer, from Purdue University, Indiana, said: “It’s standard practice for the air-conditioning systems of cruise ships to mix outside air with inside air to save energy. The problem is that these systems can’t filter out particles smaller than 5,000 nanometres. If the coronavirus is about the same size as SARS, which is 120 nanometres in diameter, then the air-conditioning system would be carrying the virus to every cabin.

“Cruise ships could minimise this problem by just using outside air and not recirculating it.”

The new Singaporean study came as airlines sought to reassure passengers that their aircraft ventilation systems do not recirculate coronavirus.

Etihad put out a statement saying its fleet is equipped with cabin air filtration systems “of similar quality to those used in hospital operating theatres”.

“In any confined area, there is a risk of contracting illnesses from other people,” the spokesman said.

“However, the risk is considered lower on aircraft because of the use of high efficiency particulate air (HEPA) filters, which are effective in capturing more than 99 per cent of airborne microbes in filtered air.”

Prof Jonathan Ball, professor of molecular virology at the University of Nottingham, criticised the idea of isolating whole families, saying: “An uninfected person poses no risk.

“If someone else within the family then develops symptoms they too should immediately isolate.

“Those in self-isolation should minimise interactions with household members.”