Yes, there are more infectious diseases popping up these days — experts say there are 7 clear reasons why

• Polio, monkeypox, marburg virus, and other infectious diseases are surging around the globe.
• Experts say there's not one thing driving the surge — a multi-layered perfect storm has been brewing for some time.

2022 has been a banner year for global infectious disease spread — and it's not just COVID.

First, there were the reports of little kids with mysterious and life-threatening liver failure across the US and Europe. Then monkeypox cases surged across the globe like never before.

Meningitis has killed at least a dozen people in Florida this year, according to state epidemiologists, while a fatal parechovirus infected newborns across several states — at least one baby died in Connecticut. In Australia and Belgium, diphtheria made a comeback, and cases of the Marburg virus are being identified for the first time ever in Ghana.

Then, just last week, New York City announced that there is polio in its wastewater, mirroring a highly unusual trend picked up in London's sewers in the spring.

"It's like all the biblical plagues are coming back, right?" Dr. Madhukar Pai, a global health expert at McGill, told Insider.

It didn't happen overnight, and it's not a direct result of the pandemic either, but disease experts agree: the pace of these infectious outbreaks is quickening.

Pai and other top-tier experts say there is no single, "simplistic" explanation. Instead, there is a wide web of at least seven powerful, interwoven issues undergirding the trend.

"It's definitely not something that we hoped would happen in public health, but it's also a situation which we feared might happen," Dr. Jay Varma, an expert in disease control and prevention at Cornell, said. "If you think about it almost like a sports event, the offense has gotten more intense — if you consider the viruses and pathogens that are out there — and our defense has weakened at the same time."

Here are the top seven factors driving disease outbreaks in 2022.

ONE: Humans and animals have more close contact

As climate change pushes people and animals out of their homes, pets and animal products travel the globe, and worldwide demand for meat reaches all-time highs, we're collectively coming in contact with all kinds of animals far more often than we used to.

"The human-animal interface has been broken," as Dr. Larry Brilliant, who helped eradicate smallpox, recently put it.

The World Health Organization estimated in 2014 that 75% of today's emerging pathogens have "originated in animals," a number that has been accelerating in recent decades.

Human-animal interaction is how COVID first spread into people. Ebola, HIV, MERS, SARS, influenza, and monkeypox all have animal reservoirs, too. When a disease pivots from animals into people, it always has the potential to spawn a new outbreak.

"The first factor that's driving transmission is increasing interaction between humans and animals, in settings that are not entirely natural, or settings that are different from the way they have been in the past," Varma said.

Deforestation, sequestration of livestock, and illicit wildlife trade — they all play a role.

"Human population is now so enormous that we will infiltrate into all sorts of ecosystems where we will encounter novel organisms — organisms to which we don't have much prior immunity," Pai added.

TWO: The pace of global travel and migration

The global, interconnected, social nature of modern life helps spread diseases between people more efficiently than ever. Any infectious disease anywhere in the world is just one flight away.

"Every time someone gets on a plane, there is some very tiny risk that they'll be carrying something new with them," Dr. Eric Rubin, editor in chief of the New England Journal of Medicine, told Insider. "The more people get on planes, the more that risk goes up."

It's a numbers game. And with the number of air travelers now skyrocketing, new pathogens can travel very fast, and very far.

In 2022, both monkeypox and polio hitched a ride on planes, infecting people on new continents. Conversely, when global travel ground to a halt in 2020, the flu essentially disappeared for a year.

THREE: The worsening climate crisis

A paper released in the journal Nature on August 8 suggests that most of the human pathogens on Earth will be "aggravated" by climate change in some way. Many of them already have been.

"Insect-borne diseases are really changing their patterns, because the insects that carry them now have a much broader range," Rubin said, citing the way that Zika — once a disease contained to Africa — has been allowed to spread across Asia and the Americas.

Chikungunya, too, is now a global disease, not the regional threat it once was.

"The tropics has moved into Europe and North America," Varma said.

FOUR: Not enough routine vaccines for kids

During the pandemic, vaccination rates plummeted across the globe in a way that hasn't been documented in decades. The WHO calls it the "largest sustained decline in childhood vaccinations in approximately 30 years."

Add to that the vaccination backsliding that was already underway in many rich countries, fueled by misinformation and vaccine hesitancy, and it was inevitable that an uptick in vaccine-preventable disease spread would happen once lockdowns, social distancing, and masking measures eased.

"We need everyone to be getting vaccinated, or we all face risks," Varma said.

In some areas of Rockland County, New York, where polio has left at least one young, unvaccinated man paralyzed this year, just 37% of little kids are up to date on their polio vaccines. (For context: nationally, nearly 93% of babies are vaccinated against polio.)

FIVE: The whole world is paying the price for years of neglecting developing countries' disease outbreaks

"All these years, Africans had monkeypox, nobody did a thing, nobody gave them vaccines," Pai said. "Now, suddenly, all the rich nations are going after — and getting — monkeypox vaccinations?"

Eventually, he said, "we pay the price" for such "archaic," "parochial," and short-sighted disease management.

"If monkeypox had been handled better in Africa, it wouldn't have spread around the world. If COVID had been handled better in low and middle income countries, new variants would not have emerged. If Ebola had been contained in West Africa, even before it spread, then it wouldn't have arrived in the US."

SIX: Our shifting perception of disease threats

We've also been shaped by our experiences during the pandemic, and we can't help but bring that knowledge into infectious disease news we read now.

In some cases, it's overblown, Pai said. "Some little outbreak happens in some corner of some market in China, immediately everybody across the world is freaking out."

In many, heightened concern is warranted.

These days, scientists also have better tools than ever for noticing what's going on — sequencing viruses, testing cases, and sounding alarm bells they couldn't have years ago.

"COVID has really changed the way we notice these things," Rubin said, speaking about average news readers and professional scientists alike. "Every day there's a disease of some sort reported somewhere in the world," he said — and that is, in part, because we are all paying more attention to them than we used to.

SEVEN: We're still not sure how COVID exposure has affected our immune systems

New disease threats are especially alarming right now because it's not yet clear to us what effect prior COVID could be having on our immune defenses.

"We will learn in the coming months and years," Pai said, "whether COVID does mess up the immune system to some degree or the other, which makes us more susceptible."

Already, he's worried that doctors' overdependence on steroid and antibiotic prescriptions during the pandemic may spur more fungal infections, superbugs, and antimicrobial resistance.

Another pandemic is coming. We could stop it — but experts fear 'we've given up'

Scientists estimate our odds of experiencing another pandemic "may double in coming decades," as disease outbreaks fueled by this wide array of interrelated, complex factors become more and more common.

But when it comes to disease prevention, "you're better off not thinking that the 10 plagues have been released simultaneously," Rubin said. "Each disease is distinct," with different biological features, distinct reasons for emerging, and varying modes of transmission and prevention.

"The answer is more investment in public health, right?" Pai said. It's often "stuff that we've given up on," he said, interventions that are "undermined," like clean drinking water, good sanitation, vaccines, equitable access to treatment and clinical care, as well as robust disease research.

"Our racism in the way we think about infectious diseases," he says, "eventually will come back and haunt us — which is what is happening."