(CNN) A widespread sense that time has split into two -- or pandemics creating a "before" and "after" -- is an experience that's associated with many traumatic events.
That's the reflection of Elizabeth Outka, a professor of English at the University of Richmond and author of "Viral Modernism: The Influenza Pandemic and Interwar Literature."
This social phenomenon is both psychologically and practically relevant, in that pandemics -- including the 1918 influenza and Covid-19 pandemics -- significantly affect how we assess and act on risk, or stay resilient, but also how we work, play and socialize.
The startling and harrowing nature of the 1918 flu and its fatal consequences induced a sense of caution that, in some places, had permanent implications for how people would respond to disease outbreaks in later decades -- such as using isolation and quarantine, according to a 2010 paper by Nancy Tomes, a distinguished professor of history at Stony Brook University.
Similarly, as the Covid-19 pandemic fades, "some existing trends will remain," said Jacqueline Gollan, a professor of psychiatry and behavioral sciences at Northwestern University's Feinberg School of Medicine in Chicago.
For example, the recent expansion and use of online shopping, telehealth services, hybrid work models and technology that allows virtual gatherings will endure, Gollan said. And "given our recognition that global crises occur," she added, "we're likely to retain an inventory of cleaning supplies and personal protection materials. We are also likely to adopt habits that improve cleanliness to promote personal or group hygiene."
As the world gradually reopens in a patchwork of ways amid other crises -- much like how states' reopenings varied after the 1918 flu and World War I -- we'll be evaluating many of the lifestyle habits we've engaged in before and during the pandemic, said CNN Medical Analyst Dr. Leana Wen, an emergency physician and visiting professor of health policy and management at the George Washington University Milken Institute School of Public Health.
These are the changes that might stick around post-pandemic.
While public health officials discouraged people from unnecessary contact with others during the 1918 flu, some people broke the rules at the height of that pandemic -- which meant that, afterward, continued compliance with safety precautions to prevent another outbreak didn't last for everyone, according to Tomes' research.
As Covid-19 restrictions ease, some people, including infectious disease experts, have felt OK shaking hands again if others are cautious or fully vaccinated. But others didn't like this social custom even before the pandemic, Wen said. Those who have been wanting to change things up may see now as the opportunity to do so.
"I also hope there will be alternatives to handshakes as in, maybe instead of doing handshakes, we have the elbow bump or the namaste greeting as the baseline of a greeting, especially between strangers," Wen said. Simply waving is another option that's taken hold.
The aftermath of the 1918 flu didn't keep everyone off of public transportation, but it did create some level of caution about how the virus could spread in such places.
As late Canadian physician William Osler observed, the flu traveled only as fast as modern transportation, meaning "it was human bodies and not some ethereal atmospheric force that spread it," Tomes wrote.
Getting the masses to be safe after the 1918 flu was difficult, but minimizing contact via isolations and quarantines seemed "to offer the best chance we have of controlling the ravages of influenza," wrote late bacteriologist Edwin O. Jordan in 1925.
Depending on future rates of cases of coronavirus, flu or other viruses, when choosing travel destinations, people might have considerations they may not have contemplated in the past, Wen said.
Travelers' recent decisions to drive to destinations close to home, rather than fly to faraway places, could indicate there are remaining concerns about Covid-19 risk, experts have said. "In the next few years," Wen added, "we are going to see coronavirus rage in parts of the world that don't have it well controlled."
"The influenza pandemic heightened a contrast between the safe home and the dangerous public space that had already become a familiar theme in the late 19th century," Tomes wrote.
The adoption of safety precautions such as coughing into handkerchiefs or avoiding crowds to try to manage the 1918 flu didn't have a ubiquitously positive impact on individuals' safety habits over the next decade, since some people abandoned such practices. However, some behaviors did influence how people and institutions responded to later disease outbreaks.
When influenza broke out in 1928, for example, some colleges and universities immediately isolated people sick with flu, Tomes wrote. "By acting quickly, college authorities at the University of Oregon limited the spread of influenza to less than 15% of the student body."
Interwar educators, advertisers and public health officials "embraced the gospel of germs with great enthusiasm," Tomes wrote. New health curricula in the 1920s introduced kindergarteners to handkerchiefs, while elementary school children learned versions of the "'handkerchief drill,' in which they sneezed into their hankies with military-style precision."
Promoting hygiene by invoking flu fears, some ads for mouthwash, cough drops and tonics reminded readers that "'a cold may be something far more dangerous,'" Tomes wrote. Women were encouraged to learn the early signs of contagious diseases so they could remind their children and husbands about careful coughing and sneezing and get them to a doctor's care as soon as possible. (Men being less disciplined about hygiene during the Covid-19 pandemic was a theme of the 1918 flu, too.)
After more than a year of wearing masks to keep ourselves and others safe during the Covid-19 pandemic, some experts foresee masks becoming a permanent part of our arsenal against coronavirus and other viruses or bacteria.
"You're sneezing a little bit, you don't know whether it's a cold or allergies -- I could imagine people putting on masks in those circumstances or people putting on masks when they're going traveling," Wen said.
Flu deaths in 1918 and World War I created substantial workforce vacancies that "provided an opportunity for women to step into lines of work previously deemed inappropriate or too dangerous, such as the textile industry and manufacturing, science and research and even medical laboratory occupations," wrote Lindsey Clark, an assistant professor at the University of Arkansas for Medical Sciences, in a March 2021 paper.
These feats were catalysts for women gaining social and financial independence, and the right to vote in 1920. While the 1918 pandemic drew women into the workforce in different ways, reports have shown the Covid-19 pandemic forced more than 2.3 million women to give up their roles.
"When schools and daycares shut down or moved to a virtual platform, women's jobs were disproportionately affected because they are still the primary care givers in the home," Clark wrote. "In one survey, 1 in 4 women who became unemployed during this pandemic did so due to lack of childcare -- double the rate of men." These disparities could urge employers and academia to consider alternatives, Clark added, such as flexible work schedules and virtual courses that would allow women more feasible access to higher education.
Difficulty finding child care and jobs as the world reopens could cause challenging or insurmountable career setbacks and financial losses, CNN has previously reported. Some schools and child care facilities are still somewhat remote, operating on shorter schedules or fully booked, according to another recent CNN report -- and some children's exposure to Covid-19 at school has caused parents to have to temporarily telework again, causing friction between resuming business as normal and the lasting pandemic effects on the community side.
In 1918, "the infrastructure of scientific research was a tiny fraction, infinitesimal compared to today," said John M. Barry, author of "The Great Influenza: The Story of the Deadliest Pandemic in History." "But the response of the scientific community was very solid today, that basically everybody dropped whatever they were doing and tried to work on the disease. Now, given the timeframe even today, we would not have developed the vaccine in time to do anything against that (1918) pandemic because it moved so quickly. And, of course, they did try to develop vaccines, but they didn't know what the pathogen was."
The research that defined viruses came several years after the 1918 pandemic. The Covid-19 aftermath will bring "measurable changes" and scientific advances, Barry added, since academic silos have broken down in a good way, allowing interdisciplinary research, collaboration and creativity that have paid off in the fields of medicine, technology and more.
READ MORE: Johns Hopkins' dashboard: The people behind the pandemic's most visited site
For example, a Johns Hopkins University-based team of infectious disease experts, data engineers, software developers and research scientists created the live coronavirus cases and deaths tracking map that governments, public health departments and news outlets -- including CNN -- have relied on for pandemic updates. This data analysis infrastructure could be useful for endeavors such as mitigating potential future epidemics and studying how climate and seasonality might have contributed to coronavirus spread.
After the Covid-19 pandemic shifted many children from in-person schooling to virtual learning, some parents have grown fond of homeschooling while others probably would rather never, ever attempt it again.
"According to a survey by EdChoice, 64 percent of parents said their view of homeschooling has become more favorable as a result of the pandemic," Joshua Coleman, a psychologist in private practice in Oakland, California, and a senior fellow with the Council on Contemporary Families, told CNN via email.
"On the other hand, many of those who were forced into it said that it was incredibly hard and not something they wanted to repeat," added Coleman, the author of "Rules of Estrangement: Why Adult Children Cut Ties & How to Heal the Conflict."
Regardless of whether parents continue to homeschool, their children could still take on extracurriculars without the commute.
"Even though I've studied remote work and taught online classes, I'd always assumed that my kids' oboe lessons and art classes would always be in person with remote instruction being a suboptimal modality for such classes," said Ravi S. Gajendran, Florida International University's chair of the global leadership and management department, and associate professor in the College of Business. "But I've been surprised at how close online classes are to the in-person experience and am more open as a consequence."
During the deadly second wave of the 1918 flu, a health committee recommended stores and factories stagger their business hours, and that people try to walk to work to prevent overcrowding on public transportation, according to the US Centers for Disease Control and Prevention. Those suggestions don't seem to have lasted long after that pandemic. In contrast, Covid-19 forced many businesses to close or go completely virtual, and one of the most significant areas in which we'll likely see lasting, post-coronavirus pandemic changes is in how work is performed, Gajendran said.
"Companies are likely to think of remote work as a business continuity mechanism, one that they can readily shift to if new variants of the coronavirus emerge that get past the protections the current vaccines afford," Gajendran said via email. "This is also likely to make hybrid work a key part of how work is performed because it provides flexibility not only with dealing with the pandemic but also offers a way of keeping operations going during other emergencies such as natural disasters and terror attacks."
More of our daily lives -- such as meetings, appointments, trainings and activities both inside and outside of work -- might be conducted online, Gajendran said. "Offices are going to be redesigned with the assumption that a lot of work and collaboration is going to involve a higher proportion of online interactions than in the past."
Resulting changes, like fewer business lunches, could shuffle cities built on downtown, in-person work, Barry said.
"I think the architecture may change and (have) more focus on ventilation in buildings. I hope they go back to the ability to open a window in an office building," he added, laughing. "That would be nice."