* I’ve told you before about how some folks are hypothesizing that the south and southwest are being hit so hard because the heat is driving people to the air conditioning at indoor venues. New York Times…

The coronavirus is finding new victims worldwide, in bars and restaurants, offices, markets and casinos, giving rise to frightening clusters of infection that increasingly confirm what many scientists have been saying for months: The virus lingers in the air indoors, infecting those nearby.

If airborne transmission is a significant factor in the pandemic, especially in crowded spaces with poor ventilation, the consequences for containment will be significant. Masks may be needed indoors, even in socially distant settings. Health care workers may need N95 masks that filter out even the smallest respiratory droplets as they care for coronavirus patients.

Ventilation systems in schools, nursing homes, residences and businesses may need to minimize recirculating air and add powerful new filters. Ultraviolet lights may be needed to kill viral particles floating in tiny droplets indoors.

The World Health Organization has long held that the coronavirus is spread primarily by large respiratory droplets that, once expelled by infected people in coughs and sneezes, fall quickly to the floor.

But in an open letter to the WHO, 239 scientists in 32 countries have outlined the evidence showing that smaller particles can infect people and are calling for the agency to revise its recommendations. The researchers plan to publish their letter in a scientific journal.

* Meanwhile…

The problem with air conditioning is that it doesn't provide enough fresh air to properly ventilate an indoor space. Most systems recirculate most or 100% of the air to reduce the cost of cooling.

— Matthew Dalton (@DJMatthewDalton) July 6, 2020

* From Harvard…

Drawing on insights from another deadly airborne disease, tuberculosis, a Harvard infectious disease expert suggested Friday that air conditioning use across the southern U.S. may be a factor in spiking COVID-19 cases and that ultraviolet lights long used to sterilize the air of TB bacteria could do the same for SARS-CoV-2.

Edward Nardell, professor of medicine and of global health and social medicine at Harvard Medical School (HMS) and professor of environmental health and of immunology and infectious diseases at the Harvard T.H. Chan School of Public Health, said that hot summer temperatures can create situations similar to those in winter, when respiratory ailments tend to surge, driving people indoors to breathe — and rebreathe —air that typically is little refreshed from outside. […]

Germicidal lamps, a technology that Nardell said is almost 100 years old, have been proven effective in protecting against tuberculosis infection and are already in use in some settings to fight SARS-CoV-2. Compared with mechanical ventilation and portable room air cleaners, the lights, according to one study, have been shown to be up to 10 times more effective, Nardell said.

* From the American Society of Heating, Refrigerating and Air-Conditioning Engineers…

Transmission of SARS-CoV-2 through the air is sufficiently likely that airborne exposure to the virus should be controlled. Changes to building operations, including the operation of heating, ventilating, and air-conditioning systems, can reduce airborne exposures.

Ventilation and filtration provided by heating, ventilating, and air-conditioning systems can reduce the airborne concentration of SARS-CoV-2 and thus the risk of transmission through the air. Unconditioned spaces can cause thermal stress to people that may be directly life threatening and that may also lower resistance to infection. In general, disabling of heating, ventilating, and air-conditioning systems is not a recommended measure to reduce the transmission of the virus.

* From late last month…

New York malls will need high quality air systems that can filter out the coronavirus before they will be allowed to reopen, Gov. Andrew Cuomo said on Monday.

“Any malls that will open in New York, large malls, we will make it mandatory that they have air filtration systems that can filter out the Covid virus,” Cuomo said at a press briefing.

High efficiency particle air filters, or HEPA filters, have been shown to help reduce the presence of Covid-19 in the air, according to a presentation from Cuomo.

Gov. Pritzker should give this serious consideration.

* In the meantime, wear a mask, particularly when you’re indoors to protect everyone else. Unfortunately for frontline workers, a national PPE shortage is looming once again…

The personal protective gear that was in dangerously short supply during the early weeks of the coronavirus crisis in the U.S. is running low again as the virus resumes its rapid spread and the number of hospitalized patients climbs. […]

In a letter to Congress last week, the health department in DuPage County, Illinois, near Chicago, said all hospitals in the county are reusing protective gear “in ways that were not originally intended and are probably less safe than the optimal use of PPE.”

The DuPage County department is a supplier of last resort that steps in when facilities have less than two weeks’ worth of gear. As of Monday, it had only nine days of some supplies at the current request level. A rise in new infections could make the supply go much faster.

The American Medical Association wrote to the Federal Emergency Management Agency, Vice President Mike Pence and members of Congress calling for a coordinated national strategy to buy and allocate gear.

This is a national defense issue. We need a national response.