How I’ll decide when it’s time to ditch my mask

For weeks, I have been watching coronavirus cases drop across the United States. At the same time, cases were heading skyward in many places in Europe, Asia and Oceania. Those surges may have peaked in some places and seem to be on a downward trajectory again, according to Our World in Data.

Much of the rise in cases has been attributed to the omicron variant’s more transmissible sibling BA.2 clawing its way to prominence. But many public health officials have pointed out that the surges coincide with relaxing of COVID-19 mitigation measures.

People around the world are shedding their masks and gathering in public. Immunity from vaccines and prior infections have helped limit deaths in wealthier countries, but the omicron siblings are very good at evading immune defenses, leading to breakthrough infections and reinfections. Even so, at the end of February, the U.S. Centers for Disease Control and Prevention posted new guidelines for masking, more than doubling the number of cases needed per 100,000 people before officials recommended a return to the face coverings (SN: 3/3/22).

Not everyone has ditched their masks. I have observed some regional trends. The majority of people I see at my grocery store and other places in my community in Maryland are still wearing masks. But on road trips to the Midwest and back, even during the height of the omicron surge, most of the faces I saw in public were bare. Meanwhile, I was wearing my N95 mask even when I was the only person doing so. I reasoned that I was protecting myself from infection as best I could. I was also protecting my loved ones and other people around me from me should I have unwittingly contracted the virus.

But I will tell you a secret. I don’t really like wearing masks. They can be hot and uncomfortable. They leave lines on my face. And sometimes masks make it hard to breathe. At the same time, I know that wearing a good quality, well-fitting mask greatly reduces the chance of testing positive for the coronavirus (SN: 2/12/21). In one study, N95 or KN95 masks reduced the chance of testing positive by 83 percent, researchers reported in the February 11 Morbidity and Mortality Weekly Report. And school districts with mask mandates had about a quarter of the number of in-school infections as districts where masks weren’t required (SN: 3/15/22).

With those data in mind, I am not ready to go barefaced. And I’m not alone. Nearly 36 percent of the 1,916 respondents to a Science News Twitter poll said that they still wear masks everywhere in public. Another 28 percent said they mask in indoor crowds, and 23 percent said they mask only where it’s mandatory. Only about 12 percent have ditched masks entirely.

Some poll respondents left comments clarifying their answers, but most people’s reasons for masking aren’t clear. Maybe they live in the parts of the country or world where transmission levels are high and hospitals are at risk of being overrun. Maybe they are parents of children too young for vaccination. Perhaps they or other loved ones are unvaccinated or have weakened immune systems that put them at risk for severe disease. Maybe, like me, they just don’t want to get sick — with anything.

Before the pandemic, I caught several colds a year and had to deal with seasonal allergies. Since I started wearing a mask, I haven’t had a single respiratory illness, though allergies still irritate my eyes and make my nose run. I’ve also got some health conditions that raise my risk of severe illness. I’m fully vaccinated and boosted, so I probably won’t die if I catch the virus that causes COVID-19, but I don’t want to test it (SN: 11/8/21). Right now, I just feel safer wearing a mask when I’m indoors in public places.

I’ve been thinking a lot about what would convince me that it was safe to go maskless. What is the number or metric that will mark the boundary of my comfort zone?

The CDC now recommends using its COVID-19 Community Levels map for determining when mask use is needed. That metric is mostly concerned with keeping hospitals and other health care systems from becoming overwhelmed. By that measure, most of the country has the green light to go maskless. I’m probably more cautious than the average person, but the levels of transmission in that metric that would trigger mask wearing — 200 or more cases per 100,000 population — seem high to me, particularly since CDC’s prior recommendations urged masking at a quarter of that level.

The metric is designed for communities, not individuals. So what numbers should I, as an individual, go by? There’s always the CDC’s COVID-19 Integrated County View that tracks case rates and test positivity rates — the percentage of tests that have a positive result. Cases in my county have been ticking up in the last few days, with 391 people having gotten COVID-19 in the last week — that’s about 37 out of every 100,000 people. That seems like relatively low odds of coming into contact with a contagious person. But those are only the cases we know about officially. There may be many more cases that were never reported as people take rapid antigen tests at home or decide not to test. There’s no way to know exactly how much COVID-19 is out there.

And the proportion of cases caused by BA.2 is on the rise, with the more infectious omicron variant accounting for about 35 percent of cases nationwide in the week ending March 19. In the mid-Atlantic states where I live, about 30 percent of cases are now caused by BA.2. But in some parts of the Northeast, that variant now causes more than half of cases. The increase is unsettling but doesn’t necessarily mean the United States will experience another wave of infections as Europe has. Or maybe we will. That uncertainty makes me uncomfortable removing my mask indoors in public right now.

Maybe in a few weeks, if there’s no new surge in infections, I’ll feel comfortable walking around in public with my nose and mouth exposed. Or maybe I’ll wait until the number of cases in my county is in single digits. I’m pretty sure there will come a day when I won’t feel the need to filter every breath, but for me, it’s not that time yet. And I truthfully can’t tell you what my magic number will be.

Here’s what I do know: Even if I do decide to have an unmasked summer, I will be strapping my mask back on if COVID-19 cases begin to rise again.

50 years ago, scientists thought a desert shrub might help save endangered whales

The sperm whale is an endangered species. A major reason is that the whale oil is heat-resistant and chemically and physically stable. This makes it useful for lubricating delicate machinery. The only substitute is expensive carnauba wax from the leaves of palm trees that grow only in Brazil … [but] wax from the seeds of the jojoba, an evergreen desert shrub, is nearly as good.

After sperm whale oil was banned in the early 1970s, the United States sought to replenish its reserves with eco-friendly oil from jojoba seeds (SN: 5/17/75, p. 335). Jojoba oil’s chemical structure is nearly identical to that of sperm whale oil, and the shrub is native to some North American desert ecosystems, making the plant an appealing replacement. Today, jojoba shrubs are cultivated around the world on almost every continent. Jojoba oil is used in hundreds of products, including cosmetics, pharmaceuticals, adhesives and lubricants. Meanwhile, sperm whale populations have started to recover under international anti-whaling agreements (SN: 2/27/21, p. 4).

How a virus turns caterpillars into zombies doomed to climb to their deaths

Higher and higher still, the cotton bollworm moth caterpillar climbs, its tiny body ceaselessly scaling leaf after leaf. Reaching the top of a plant, it will die, facilitating the spread of the virus that steered the insect there.

One virus behind this deadly ascent manipulates genes associated with caterpillars’ vision. As a result, the insects are more attracted to sunlight than usual, researchers report online March 8 in Molecular Ecology.

The virus involved in this caterpillar takeover is a type of baculovirus. These viruses may have been evolving with their insect hosts for 200 million to 300 million years, says Xiaoxia Liu, an entomologist at China Agricultural University in Beijing. Baculoviruses can infect more than 800 insect species, mostly the caterpillars of moths and butterflies. Once infected, the hosts exhibit “tree-top disease,” compelled to climb before dying and leaving their elevated, infected cadavers for scavengers to feast upon.
The clever trick of these viruses has been known for more than a century, Liu says. But how they turn caterpillars into zombies doomed to ascend to their own deaths wasn’t understood.

Previous research suggested that infected caterpillars exhibit greater “phototaxis,” meaning they are more attracted to light than uninfected insects. Liu and her team confirmed this effect in the laboratory using cotton bollworm moth caterpillars (Helicoverpa armigera) infected with a baculovirus called HearNPV.

The researchers compared infected and uninfected caterpillars’ positions in glass tubes surrounding a climbing mesh under an LED light. Uninfected caterpillars would wander up and down the mesh, but would return to the bottom before pupating. That behavior makes sense because in the wild, this species develops into adults underground. But infected hosts would end up dead at the top of the mesh. The higher the source of light, the higher infected hosts climbed.

The team moved to the horizontal plane to confirm that the hosts were responding to light rather than gravity, placing caterpillars in a hexagonal box with one of the side panels illuminated. By the second day after infection, host caterpillars crawled to the light about four times as often as the uninfected.

When the researchers surgically removed infected caterpillars’ eyes and put the insects in the box, the blinded insects were attracted to the light a quarter as often as unaltered infected hosts. That suggested that the virus was using a caterpillar’s vision against itself.

The team then compared how active certain genes were in various caterpillar body parts in infected and uninfected larvae. Detected mostly in the eyes, two genes for opsins, the light-sensitive proteins that are fundamental for vision, were more active after an infection with the virus, and so was another gene associated with vision called TRPL. It encodes for a channel in cell membranes involved in the conversion of light into electrical signals.

When the team used the gene-editing tool CRISPR/Cas9 to shut off the opsin genes and TRPL in infected caterpillars, the number of hosts attracted to the light in the box was cut roughly in half. Their height at death on the mesh was also reduced.

Baculoviruses appear capable of commandeering the genetic architecture of caterpillar vision, exploiting an ancient importance of light for insects, Liu says.

Light can cue crucial biological processes in insects, from directing their developmental timing, to setting their migration routes.

These viruses were already known to be master manipulators in other ways, tweaking their hosts’ sense of smell, molting patterns and the programmed death of cells, says Lorena Passarelli, a virologist at Kansas State University in Manhattan, who was not involved with the study. The new research shows that the viruses manipulate “yet another physiological host process: visual perception.”

There’s still a lot to learn about this visual hijacking, Passarelli says. It’s unknown, for instance, which of the virus’s genes are responsible for turning caterpillars into sunlight-chasing zombies in the first place.

New images reveal details of two bacteria’s molecular syringes

Some bacteria carry tiny syringes filled with chemicals that may thin out competitors or incapacitate predators. Now, researchers have gotten up-close views of these syringes, technically known as contractile injection systems, from a type of cyanobacteria and a marine bacterium.

Figuring out how key parts of the molecular syringes work may help scientists devise their own nanomachines. Artificial injection machines could direct antibiotics against troublesome bacteria while leaving friendly microbes untouched.

Genes encoding pieces of the injection machinery are found in many bacterial species. But, “just by looking at the genes, it’s quite hard to predict how these contractile injection systems work,” says Gregor Weiss, a cellular structural biologist at ETH Zurich.
So Weiss and colleagues examined bacterial syringes using cryo-electron microscopy, in which cells are flash frozen to capture cellular structures as they typically look in nature (SN: 6/22/17).

Previously, researchers have found syringes anchored in some bacteria’s outer membranes, where the bacteria can shoot their payload into cells they bump into. Other species’ injectors squirt their contents into the environment.

But in a type of cyanobacteria called Anabaena, the syringes are in an unusual place, nestled in the membrane of the internal structure where the bacteria carry out photosynthesis, Weiss and colleagues report in the March Nature Microbiology. Buried inside the cells, “it’s hard to imagine how [the syringes] could get out and interact with the target organism,” Weiss says.
Anabaena may use its syringes against itself to trigger programmed cell death when the cyanobacteria come under stress. In the team’s experiments, ultraviolet light or high salt levels in water triggered some syringes to dump their payload. That led to the death of some Anabaena cells in the long chains that the cyanobacteria grow in, forming hollow “ghost cells.”

Ghost cells shed their outer wall and membrane, exposing unfired syringes in the inner membrane to the outside. The ghosts may act like Trojan horses, delivering their deadly payload to predators or competitors, the team hypothesizes. The researchers haven’t yet found which organisms are the probable targets of Anabaena’s syringes.

Inside a type of marine bacteria called Algoriphagus machipongonensis, the story is a bit different. Here, the syringes have a different architecture and float unmoored within the bacterial cell, ETH Zurich’s Charles Ericson and colleagues report in the March Nature Microbiology. The injectors are also found in the liquid in which the bacteria are grown in the laboratory, but how they get out of the cell is a mystery. Perhaps they are released when the bacteria die or get eaten by a predator, Ericson says.

The team also found two proteins loaded inside the Algoriphagus’ syringes, but what those proteins do isn’t known. The researchers tried genetically engineering E. coli to produce one of the proteins, but it kills the bacteria, says study coauthor Jingwei Xu, also at ETH Zurich.
Comparing the structures of syringes from various species, the researchers identified certain structures within the machines that are similar, but slightly different from species to species. Learning how those modifications change the way the injectors work may allow researchers to load different cargoes into the tubes or target the syringes against specific bacteria or other organisms. “Now we have the general blueprint,” Ericson says, “can we re-engineer it?”