MILWAUKEE (SPECTRUM NEWS) — In recent months, the scientific world has seen a steady flow of research updating what we know about the novel coronavirus, SARS-CoV-2, and how it affects humans. Because the virus is so new, researchers are still grappling with many questions about its function. And because of the nature of the scientific process, no single study can completely answer those questions. Instead, new research is constantly challenging our understanding of the pandemic.

Here, we explore some recent studies that have shed new light on the virus and its impacts.

Coronavirus may attack the brain too

Since the pandemic started, we’ve thought of SARS-CoV-2 as a respiratory virus first and foremost. The virus infects the lungs, causing the central symptoms like cough and shortness of breath that we’ve come to recognize. 

But there’s growing evidence that the virus also makes its way into many other parts of the body — including the heart, kidneys, and, new research shows, possibly the brain as well.

A recent study from Yale researchers indicated that the virus might be able to take over brain cells called neurons and use their mechanisms to produce more viral copies. 

“Altogether, our study provides clear demonstration that neurons can become a target of SARS-CoV-2 infection, with devastating consequences,” the authors write in the study, which was published as a preprint and has not yet gone through the peer review process.

Doctors have been noticing neurological symptoms in COVID-19 patients for some time now, ranging from fatigue, inattention, and general “brain fog” to intense delirium and strokes. 

The Yale researchers believe that such symptoms could be a result of the virus directly infecting brain cells. They used three settings to test the virus’s ability to infect the brain: lab-grown “organoids” modeled after human brain tissue, mice infected with the virus, and brain tissue from patients who died with COVID-19. 

In all three of these setups, the researchers found that the coronavirus could infect neurons — even though the surface protein ACE2, which the virus uses to invade cells, are thought to be less common in the brain. They concluded that the virus could cause intense damage by taking over neurons and using their machinery to multiply, while simultaneously killing off neighboring cells by using up all the available oxygen.

“If the brain does become infected, it could have a lethal consequence,” Akiko Iwasaki, the study’s lead author, told The New York Times.

Still, questions remain about whether these brain cell infections are widespread, and if they’re actually the main driver of the neurological symptoms. Experts say these symptoms might also have to do with the overstimulation of the immune system, which can cause other problems in the body as it goes into overdrive trying to respond to the virus.

Like with many aspects of this virus, more research is needed to fully understand how the virus can affect the brain and nervous system — and how doctors can best treat the COVID-19 patients facing a wide array of neurological problems.

The pandemic is setting the world back on development goals

Along with the sickness and death directly caused by COVID-19, the pandemic will likely have major and long-lasting effects on the efforts to address public health, poverty, and education across the world, organizations warn.

A report from the United Nations this month said that COVID-19 could lead to an increase in preventable child deaths for the first time in decades. 

In a survey of 77 countries over the summer, UNICEF researchers found that around 68% had reported some kind of disruption in health checks or immunization for children. Agencies reported that financial difficulties, shutdowns of services and transportation, and fear of getting infected with COVID-19 all played a role in limiting access to children’s health care.

“When children are denied access to health services because the system is overrun, and when women are afraid to give birth at the hospital for fear of infection, they, too, may become casualties of COVID-19,” UNICEF Executive Director Henrietta Fore said in a press release. “Without urgent investments to re-start disrupted health systems and services, millions of children under five, especially newborns, could die.”

Another report from UNICEF and humanitarian organization Save the Children estimated that the pandemic has pushed 150 million more children into multidimensional poverty. That’s a 15% increase since before the pandemic, and officials warned that the situation will probably get worse in the months to come.

In its annual Goalkeepers Report, the Bill and Melinda Gates Foundation also shared some dire news: “By nearly every indicator, the world has regressed” during the pandemic, the foundation shared in a press release.

The report measures the world’s progress toward the UN Sustainable Development Goals, which aim to address global challenges like poverty, inequality, climate change, and justice. In recent years, the world has made progress on all 18 of these goals; this year, though, we’ve moved backward on “the vast majority,” according to the report.

Extreme poverty has increased by 7% worldwide because of the pandemic, the foundation finds. And vaccine coverage, used here as a measure of how well health systems are functioning, is dipping to levels last seen in the 1990s — “setting the world back about 25 years in 25 weeks,” the report says.

“One of the most troubling things about this pandemic is that by disrupting health systems and the global economy, it’s starting to erase the progress people have made toward living healthier, more productive lives,” Melinda Gates said in a press release.

Huge genetic study shows the coronavirus mutating

A research team in Houston released a new preprint study this month looking at the genetic sequences of 5,085 coronavirus samples — likely making it the largest study of its kind in the U.S. The study shows that the virus has accumulated some mutations as it’s continued its spread, though there isn’t evidence that the virus has become any deadlier or caused more severe symptoms. 

Viruses tend to accumulate mutations as they spread. Every time a virus makes a new copy, there’s a potential for a copying error that could lead to a mutation. 

Generally, coronaviruses seem to change more slowly than other viruses and have a “proofreading” enzyme that can correct mistakes in the copying process. Data suggests coronaviruses change at about half the rate of influenza and one-quarter the rate of HIV.

But as the virus has spread widely across the world, it’s gotten more and more opportunities to change.

“We have given this virus a lot of chances,” study author James Musser told The Washington Post. “There is a huge population size out there right now.”

The scientists noted that one particular strain of the coronavirus grew more prevalent over the course of their study, making up almost all of the infections in Texas’ second peak over the summer. This strain includes a mutation that scientists have dubbed “D614G,” which changes one amino acid in the spike protein — the part of the virus that attaches to our cells. 

Between March 5 and May 11, which the researchers classified as the first wave of infections, 82% of the samples they collected in Houston had this mutation. But in the second wave, from May 11 to July 7, the mutation showed up in 99.9% of samples. 

Other scientists have also reported that the strain has become common elsewhere in the U.S. and across the world. Musser and his team concluded that this growing prevalence means the mutation makes the virus more contagious, allowing it to out-compete other versions. 

Still, some experts say that strain of the virus might have just gotten lucky, essentially, in its spread. The mutation isn’t new — experts saw it show up as early as January — and because pretty much all humans are susceptible at the moment, there’s no real evolutionary pressure on the virus to keep changing.

“As far as the virus is concerned, every single person that it comes to is a good piece of meat,” William Hanage, an epidemiologist at the Harvard T. H. Chan School of Public Health, told Nature.

Either way, experts say it’ll be important to keep sequencing the virus’s genes, especially as efforts continue to develop effective vaccines. 

Evidence builds for aerosol transmission, though debates continue

Can the coronavirus spread through tiny aerosols? It’s a question that has been argued constantly over the course of the pandemic, and one that has important implications for how we think about protecting ourselves.

A growing number of experts, officials, and agencies have acknowledged the likelihood that the virus can travel in aerosol form, which means it could stick around in the air longer and spread farther than in the heavier droplet form.

The debate has been ongoing for months. Back in July, more than 200 scientists signed an international open letter pushing the World Health Organization to acknowledge the potential for airborne spread, as agencies were still saying that most infections came from larger droplets or “fomites” — objects contaminated with the virus. 

“We are concerned that the lack of recognition of the risk of airborne transmission of COVID-19 and the lack of clear recommendations on the control measures against the airborne virus will have significant consequences,” the authors wrote.

The WHO has since updated its guidance to say that aerosol transmission “cannot be ruled out,” though they say more study is needed.

Recently, the Centers for Disease Control and Prevention added another layer of complication when they first posted, then quickly walked back, an update about airborne transmission on their website.

In September, the CDC updated its guidance on “How COVID-19 Spreads” to say that the virus spreads most commonly through “respiratory or small particles, such as those in aerosols.” But days later, they removed that language, saying the change was posted in error.

Much of our public health guidance would remain the same if aerosol transmission is possible: Wear a mask, limit your interactions, wash your hands, keep your distance. But airborne spread would also mean that we should stress the importance of ventilation and airflow, and generally understand that 6 feet of distance might not be enough to protect us. 

Though the information we have isn’t perfect, many experts have said the evidence should be enough for us to take such extra precautions. Outbreaks have already been reported in closed settings like restaurants, bars, and churches, and especially moving toward colder weather, activities may be moving indoors into more shared-air spaces.

In a column for TIME last month, chemistry professor Jose-Luis Jimenez wrote that “the evidence in favor of aerosols is stronger than that for any other pathway, and officials need to be more aggressive in expressing this reality if we want to get the pandemic under control.”

And in an interview last week, infectious disease expert Anthony Fauci agreed that the evidence was enough.

“I believe and I think there's good enough data that aerosol transmission does occur,” Fauci said.