The two most common questions about Covid-19 tell a larger story about the pandemic

There's a lot to be confused about when it comes to the Covid-19 pandemic. There's a vaccine race to keep up with, the dynamics of social distancing, and the lingering question: How long will it all last?

Inverse asked readers about which pandemic topics they thought were the most confusing. More than 1,000 people wrote in and two topics rose to the top.

Thirty-four percent of Inverse's survey respondents thought the public was still the most confused about mask effectiveness. That was followed by 26 percent of people, who believed that the asymptomatic spread of the virus was especially perplexing. The two questions — and their answers below — are two vital subplots in the larger story of this pandemic: Misinformation thrives when the facts aren't clear.

About this series — Inverse polled you, our readers, about what you see as the biggest questions regarding Covid-19. More than 1,000 people responded. Read more stories below:

• Scientists answer the biggest Covid-19 vaccine question
• Remdesivir, Dexamethasone: The most confusing treatment questions, answered
• The most common social distancing confusion, explained by medical experts

Do coronavirus masks work?

When the pandemic began, government officials like the Surgeon General made it clear that masks were to be reserved for healthcare workers – who at the time, were facing disastrous shortages of personal protective equipment.

Then in April, after a viral social media movement took hold abroad and new evidence emerged, the CDC's stance on masks changed.

Catherine Clase, an associate professor of medicine at McMaster University, explains that at the outset of the mask debate, there wasn't much research showing whether they worked to control viruses outside of a hospital. Public health officials that were honest about the uncertainty ended up with an unexpected consequence.

"Instead of inspiring public confidence, which transparency should do, that had a negative unintended consequence of making people feel that the decision was not as clear cut," she tells Inverse.

Anthony Fauci, the National Director of Allergy and Infectious Diseases has also noted that there were missteps in communicating about masks. Today, there's an abundance of evidence demonstrating how masks work – even homemade cloth masks.

In a recent review, and a plain-language summary, published in Annals of Internal Medicine, Clase notes that masks don't stop every virus-laden droplet you encounter. Rather, they stop enough of them to make the environment safer for those around you.

The overall effect is a safer world for everyone. She explains it elegantly:

"Every virus-laden particle retained in a mask is not available to hang in the air as an aerosol or fall to a surface to be later picked up by touch."

That's even the case for smaller aerosols – droplets that are less than five microns large, but nonetheless help the virus spread. Aerosols sometimes begin as large droplets, and then dehydrate into smaller droplets as they encounter drier air, Clase explains.

"If you can stop them as larger particles within a few centimeters of the lips, then I think that gives us some theory to explain how masks may be helpful."

Her literature review also highlights a 2013 paper showing that cloth masks made of T-shirts could stop 51 percent of aerosols laden with a virus smaller than the flu. Those made from tea towels could stop 72 percent of those aerosols. Surgical masks were still best and stopped 90 percent.

There are countless visualizations showing just how effective masks are for stopping droplets during talking (which can release thousands of droplets), sneezing, or coughing. For instance, one visualization that compared surgical masks to face shields showed that face shields allowed smaller aerosols to drift away from a coughing mannequin – a face mask allowed far fewer aerosols to escape.

The United States never implemented a federal mask mandate, but individual cities and states have.

A paper published in Health Affairs analyzed Covid-19 case data from 15 states between April and May in states that implemented mask mandates. Within the first day after a mandate was put in place, they found that the growth rate of new cases declined by one percent. By day 22, that rate declined by about two percent.

That's not as marginal as it may seem, Clase points out. The authors estimate a ballpark measure of how many cases those mandates prevented by the end of May: somewhere between 230,000 to 450,000. They were about 16 to 19 percent as effective as school closings, bans on gatherings, and closure of businesses – far more socially disruptive policies than wearing a cloth on your face.

Masks aren't perfect. But they are one of the best tools we have; CDC director Robert Redfield suggested that masks may control the pandemic even better than a vaccine. And additional modeling studies have noted that if 50 percent of people wore masks, we could flatten the Covid-19 curve.

"We shouldn't let the perfect be the enemy of the good," Clase concludes. "Almost any mask is going to be providing some degree of protection."

Can asymptomatic people spread Covid-19?

The experience of Covid-19 comes in many flavors. Some 942,000 people have died of this disease worldwide. Others escape without so much as a tickle in their throat.

The latter are asymptomatic cases: They have the virus and can spread it, but may not even know they have it.

Research has shown that they play a large role in sustaining the pandemic. One June PNAS paper suggested that even if all symptomatic cases were controlled, the virus may still surge. To avoid future outbreaks, the authors estimate that one-third of asymptomatic cases must be identified.

It's easier to visualize the nightmare of asymptomatic spread in a case study. A paper in Nature outlines how asymptomatic spread took over Vó, Italy, a town 31 miles from Venice.

The scientists tested Vó residents twice: once around the time a lockdown was implemented and again when lockdown was lifted. They were able to test 86 percent of the population (2,812 people) the first time and 71 percent (2,343 people) the second time. At the end of lockdown, about 1.2 percent of the town had Covid-19. Of those they tested, 42.5 percent never showed symptoms.

Ilaria Dorigatti is a co-author of that case study and a lecturer at Imperial College London. She tells Inverse that asymptomatic spread is clearly a problem, but we're still not sure how exactly and how well asymptomatic people spread the disease compared to those with symptoms.

"Quantifying the contribution of asymptomatic infections to the transmission of SARS-CoV-2 remains an open question and is a research priority," she tells Inverse.

We're also unsure of why some people never show symptoms, she adds, though there's ongoing research in a few areas including:

• How the immune system fights off infection
• The amount of virus someone is exposed to
• The viral load (the amount of virus in the body, the study in Vo found no significant differences in viral load for asymptomatic people compared to symptomatic people)
• Demographics like age and sex
• Pre-existing conditions
• Potentially genetics or other unknowns.

What we are sure of is how to control the impact of asymptomatic spreaders: Through continuous testing, and contact tracing of people who test positive. Other public health measures like limiting large gatherings also helps — especially if a gathering includes someone who unknowingly has the virus.

"Super-spreading events typically occur at gatherings, and more frequently in indoor spaces with poor ventilation," Dorigatti says. "This explains why in some countries interventions focus on limiting the size of gatherings."

Importantly, there's one tool that can help mitigate the impact of asymptomatic spreaders even more: a mask.