“Over the past year, the lack of consistent and cohesive messaging among scientists and lawmakers has seeded confusion over what makes up risky behavior, what activities should be avoided and why. That is beginning to change as consensus builds and scientists better understand the virus.
In the U.S., scientists at first advised people against wearing masks, in part because of shortages, while the idea of stay-at-home orders received severe pushback from some lawmakers. Early in the pandemic, testing was limited to people with symptoms, also partly due to shortages. That advice has shifted, but a year later, sufficient testing remains a critical issue.
Countries such as New Zealand and others in Asia adhered to a combination of basic mitigation strategies from the start—particularly masking, large-scale testing and lockdowns that broke transmission chains. They have tended to fare better than those that didn't.
In one of his first moves, President Biden signed executive orders to require masks be worn on federal property and at airports and other transportation hubs. The administration said it is focusing on increasing the availability of vaccines, and also stressed the importance of widely available testing, which still lags in low-income and minority communities .
The current scientific playbook follows from two of the biggest research insights since the start of the pandemic. First, individuals who aren't showing symptoms can transmit the virus . Infectious-disease experts worry most about this silent spread and say it is the reason the pandemic has been so hard to contain. While visibly sick people can pass on the virus, data cited by the Centers for Disease Control and Prevention estimate that 40% to 45% of those infected never develop symptoms at all. With the new viral variants that can transmit more readily, the potential for silent spread is even higher , infectious-disease experts said.
Secondly, researchers now know that tiny airborne particles known as aerosols play a role in the spread of Covid-19. These can linger in the air and travel beyond 6 feet.
An early hallmark of the pandemic response focused on the risk of transmission through large respiratory droplets that typically travel a few feet and then fall to the ground. Businesses rushed to buy plexiglass barriers, creating shortages.
The barriers can be good at preventing larger virus-containing droplets from landing on and infecting healthy individuals. They may offer some protection in shielding workers who have brief face-to-face interactions with many people throughout the workday, such as cashiers and receptionists, some occupational-health experts said.
Yet in settings like offices, restaurants or gyms, the role of the barriers is murkier, because activities like talking loudly and breathing deeply create aerosols that can waft on air currents and get around shields.
Also, installing such barriers could affect airflow throughout the space, environmental-health experts said. It is possible they could limit proper ventilation , making things worse, they said.
"There seems to be an assumption that particles are going to get stopped by the barriers, which is simply not true," said Lisa Brosseau, an industrial hygienist and research consultant for the University of Minnesota's Center for Infectious Disease Research and Policy. Airborne particles ferrying the virus "really distribute all over the place."
The emphasis on intense surface cleaning has diminished as scientists have come to understand that indirect transmission through contaminated surfaces doesn't play as critical a role in the spread of Covid-19 as they thought in the early days of the pandemic. In September, the CDC published sanitation guidelines for offices, workplaces, homes and schools that said that, for most surfaces, normal, routine cleaning should suffice, and that frequently touched objects, such as light switches and doorknobs, should be cleaned and disinfected.
"Sanitation is important in general always," said Deborah Roy, president of the American Society of Safety Professionals. "The idea is we went overboard at the beginning because of the amount of unknowns. Now, we're in a situation where we have more information."
Temperature checks have become less popular among some employers because scientists now know that not all Covid-19 patients get fevers. One large study published online in November in the New England Journal of Medicine showed only 13% of Covid-19 patients reported a fever during the course of their illness.
Scientists now understand that brief encounters with an infected person can lead to spread , according to an October case study—an advance from earlier, when the rule of thumb was to avoid close contact for 15 consecutive minutes or longer. The report urged people to consider not just time and proximity in defining close contact with a Covid case, but also ventilation, crowding and a person's likelihood of generating aerosols. Following the report, the CDC changed its definition of close contact to a total of 15 minutes or more over a 24-hour period.
Fresh air and effective filters indoors are important because they can remove virus particles before they have time to infect.
Masks offer a similar benefit, by lowering the amount of particles that infected individuals emit. Some scientists say there could be a benefit to doubling up on masks , as a second layer may improve both filtration and fit, so long as the masks are worn correctly.
A study published in October found that in countries where mask wearing was the norm or where governments put in place mask mandates, coronavirus mortality rates grew much more slowly than in countries without such measures. This fall, the CDC said that masks also offer some personal protection by reducing a wearer's exposure to infected particles.
The combination of airborne particles and personal interactions, even among people who don't feel ill, can turn wedding receptions , plane rides and choir practices into superspreading, potentially deadly events.
"For Covid, those two factors—asymptomatic spread and aerosolization—is what made mask-wearing so essential," said Megan Ranney, emergency physician and assistant dean at Brown University.
Airborne transmission experts recommend that building managers pump in clean, fresh air between three to six times an hour and that they install filters that are proven to effectively trap and remove a substantial number of virus-carrying particles.” [1]
And in Lithuania, it is required to ventilate work premises only every hour. Strange are those who write such rules.
1. New Playbook for Covid-19 Protection Emerges After Year of Study, Missteps; Mask-wearing, good air flow and frequent rapid tests are more important than surface cleaning, temperature checks and plexiglass. Scientists say America needs to double down on protection protocols as potentially more-contagious coronavirus variants take hold and vaccines are slow to roll out. Hernandez, Daniela; Toy, Sarah; McCabe, Caitlin. Wall Street Journal (Online); New York, N.Y. [New York, N.Y]26 Jan 2021.
