An experiment using smoke to simulate how aerosol infections work is seen in this photo provided by Aichi Prefectural University in Nagakute, Aichi Prefecture.

       TOKYO -- The new omicron variant of the coronavirus is spreading unchecked across the world. And recent research suggests that omicron virus particles floating in the air in aerosols may stay viable longer than their delta variant cousins -- the version that fueled Japan's fifth infection wave -- thanks to a kind of improved protective coating, potentially boosting its transmissibility.

       It is well known now that the coronavirus spreads when someone breathes in virus particles in tiny droplets -- aerosols -- expelled when an infected person exhales or coughs. The same mechanism is at work for other airborne pathogens like tuberculosis and measles, and all could be called "aerosol infections."

       There have been multiple reports of omicron being transmitted by such aerosols as well. In a Hong Kong hotel, a person was infected by another guest staying in a room across the hall. In another case, 61 of some 600 passengers on flights from South Africa to the Netherlands were found to have COVID-19, 13 of them with omicron.

       "Previous variants are being spread by aerosols too," noted Nobuaki Shimizu, a professor and infection control expert at Aichi Prefectural University in Nagakute, Aichi Prefecture. "In places like on the Diamond Princess (cruise ship) and in hospitals, stale air containing the virus was recycled repeatedly, so there were a lot of cluster infections even among people staying in different rooms. There needs to be an investigation into exactly what is happening with the ventilation in that Hong Kong hotel and on airplanes, but it's certain that there are aerosol omicron infections."

       But how is omicron spread through the air? A University of California research team created an aerosol containing the coronavirus and, using the Summit supercomputer at the Oak Ridge National Laboratory in Tennessee, simulated the mechanics of an aerosol spread. According to the team's findings, which have not yet been peer reviewed, it appears that substances called mucins -- proteins from the lung's mucus lining -- in human aerosols attract the spike proteins studding the coronavirus. The reason is simple physics: the mucins are negatively charged, and the spike proteins have a positive charge, so the mucins seem to gather around the virus particles.

       According to a New York Times report on the research, the team believes the mucins that bind with the spike proteins form a protective coating, preventing damage to the virus. And the omicron variant acquires a more effective coating than the delta variant, meaning it could stay infectious outside the body for longer.

       Total coronavirus infection numbers remain low in Japan. But the dry air that accompanies the coming of winter makes it easier to catch aerosol-borne infections, and it is thought that the increased social activity around the end of the year will boost transmission risks.

       Professor Shimizu pointed out that previous variants such as alpha and delta began their spread inside the country at times just like now, when overall infections were at a low ebb. In South Africa, too, omicron case numbers began to grow around the time the delta variant had been brought under control. "It's easier for new variants to spread when older ones are on the decline, as that means the new version has fewer competitors," said Shimizu.

       Asked about steps Japan should take to counter the potential spread of omicron domestically, Shimizu pointed out that "urethane foam masks have almost no anti-infection effect." He added, "Making sure there are no gaps (between your mask and your face), such as by wearing two unwoven cloth masks, is effective, as is making sure to maintain proper ventilation."

       On how the virus is transmitted, the Ministry of Health, Labor and Welfare had previously only mentioned fluid spray and close contact. However, in October 2021 the ministry updated the information on its website to acknowledge aerosol infections. It also amended the transmission route information in its diagnosis and treatment advice to doctors, from "spray and close contact," to "spray and aerosol."

       (Japanese original by Naomi Hayashi, Lifestyle and Medical News Department)

       Font Size S M L Print Timeline 0