Why Infectious Disease Outbreaks Are Becoming So Common

SARS-CoV-2. Monkeypox. Polio. Marburg. These viruses are no longer familiar just to public-health experts, but household names around the world, thanks to their recent incursions into human populations. People have always confronted pathogens of all sorts, but the attacks are becoming more commonplace, and more intense, than they ever have before.

“We are going through an era of epidemics and pandemics, and they are going to be more complex and more frequent,” says Jeremy Farrar, director of Wellcome, a global health charitable foundation that addresses health challenges. “We tend to see each [outbreak] in its own right, as an individual episode. But the truth is that they are almost all a symptom of underlying drivers, all of which are part of 21st-century life.”

The world has seen polio outbreaks before, for instance, as well as monkeypox clusters and cases of Marburg, a cousin of the deadly Ebola virus. We’ve even seen earlier versions of SARS-CoV-2 in the coronavirus outbreaks of 2002 and 2012. So why are these outbreaks piling up, seemingly all of sudden, and at the same time?

The explanation lies in a gathering perfect storm of factors that taps into nearly every way we live our contemporary lives—from the ubiquity of worldwide travel to humans’ deeper encroachment into previously untouched natural habitats and the modernization that has led to climate change, urbanization, and overcrowding. Even the instantaneous and unfiltered way we communicate on social media is contributing, since misinformation is often shared, believed, and elevated to the same degree as trustworthy messages. Then there is the mercurial and increasingly unstable balance of geopolitics driving millions from their homes and into refugee camps and migrant housing, which are fertile grounds for infectious diseases to spread.

Simply put, the multitude of infectious diseases facing the world today is “just the evolution of microbes and humans coming to a collision course,” says Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

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That interface is occurring more frequently as people creep closer to nature. Coronaviruses, for example, live in bats, while influenza viruses inhabit bird populations; both viruses spread wherever the animals roam, which increasingly involves regions where they come into contact with people.

Deforestation, climate change, and urbanization make such interactions more likely. In the case of Ebola, say experts, the largest outbreak of the disease in West Africa in 2014 was likely amplified by the fact that urbanization had concentrated more people into densely packed cities than had been the case when the virus was first reported in people in the 1970s. “In the 1990s and 2000s, Ebola hadn’t changed; what changed was that Ebola had been a rural-village disease that had affected isolated villages, but hadn’t reached big urban centers,” says Osterholm. Urbanization and overcrowding in large cities where sanitation and social distancing aren’t always practiced mean that viruses and bacteria find it easier to seek new hosts.

Improvements in travel have also come with urbanization. And air travel doesn’t just transport people; it also brings whatever viruses and bacteria they may be harboring to other parts of the world in a matter of hours. The recent monkeypox outbreak, which spread to 94 countries in three months, is one example. The virus, which is endemic in Central and Western Africa, hitched rides on people from that region to festivals around the world, and then landed in countries where cases are rarely reported. “If monkeypox had happened 100 years ago, the world would hardly have seen any real global challenge, because transportation was so slow and incomplete that it wouldn’t have spread the way modern air travel can make happen,” says Osterholm.

There may be another powerful force at work making such confrontations between people and pathogens more significant and even more deadly. Viruses and other microbes aren’t individual agents of disease, but exist as a dynamic and ever-evolving community. Every encounter with a human is a chance for pathogens like viruses to become fitter and more adept at infecting and causing disease in people. That’s likely the case with coronaviruses; SARS and MERS, for example, caused infections with high fatality rates but were not transmitted very effectively from person to person. The next-generation virus SARS-CoV-2, however, finally found a way to spread easily from one human host to another.

Something similar may be occurring with monkeypox. U.S. scientists, working with their counterparts in Nigeria, where the virus is endemic, began seeing changes in the virus several years ago. “They were seeing that the virus was more efficient at transmitting disease from human to human,” says Dr. Raj Panjabi, senior director for global security and biodefense at the White House National Security Council. “That’s an alarm bell. It signals that maybe the transmission changed because the virus adapted better to [live] among us.” Farrar notes that with each previous monkeypox outbreak in Africa, the chain of contagion—one person infecting another—has gradually gotten longer, “and the infections last longer,” he says. “Instead of one or two people infected, it’s now five to six people, then 10 to 12 people.”

Osterholm says all of these converging factors puts the world in a perilous place. “Any one of these on their own is a problem for public health,” he says. “Add them all together, and you get a crisis.”

Do humans have a chance? “I think we are at the most vulnerable we have ever been in my professional career,” says Farrar. He sees the biggest threat to people’s ability to stave off major pandemics coming from our inability to cooperate, share public-health information, and mount an effective defense against infectious diseases. “Putting aside biodiversity, land use, protection of habitats, and social media, the biggest challenge is geopolitics,” he says, citing the aggressions in Eastern Europe, East-West tensions and the inequity of health resources and health infrastructure between developed and developing countries. “Unless we resolve geopolitical issues, then I’m afraid that we won’t have sight of what is emerging from China, Europe, Africa, the Americas, and Southeast Asia. We’ve got to get back to understanding that the world is very small, and we are interconnected.”

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He is optimistic that COVID-19 and the other ongoing outbreaks may have finally awakened a global awareness of this need for collaboration. The World Bank recently mobilized a $10 billion annual fund dedicated to helping countries in the developing world improve their surveillance methods for detecting and—most importantly—sharing information about unusual cases of infectious diseases that could represent new public-health threats. The funds will bolster these countries’ networks of community health workers and lab-testing capabilities, as well as their access to tests, vaccines, and treatments. Farrar notes that global contributions to the fund, including from China, are hopeful signs that “maybe this is one way to bring the world back together again” around the challenge of pandemic preparedness.

But developed countries need to lead by example. The U.S. is making some strides; President Biden revived the Directorate for Global Health Security and Biodefense, which Panjabi heads, after it was dissolved during the Trump Administration. Biden has proposed a record $88-billion investment in preparing the country against the next pandemic threat, spread over five years, that would prioritize investment in testing, vaccine, and treatment research, as well as in monitoring for new diseases and building up supplies of personal protective equipment and trained health care workers who could be deployed during a public-health emergency. “There has never been that much money requested for pandemic preparedness and global health security ever,” says Panjabi.

Securing that money will be an enormous challenge. But such investment is ultimately the most cost-effective way to combat public-health threats, before cases of a new disease turn into clusters—then outbreaks, epidemics, and pandemics. “The more we do to strengthen national public-health institutes—not just in the U.S. but around the world—the more prepared we will be,” says Panjabi. “These investments build towards the ambitious goals, such as developing effective vaccines and therapeutics within 100 days of identifying a threat, producing sufficient quantities to vaccinate the United States population within 130 days, and supporting surge production to rapidly meet global needs.”

Responding quickly and effectively will have to become routine if we are to weather the onslaught of outbreaks sure to head our way. “Microbial evolution is alive and well,” says Osterholm. “We are fighting an enemy that is growing and changing every day to accommodate as the world changes.”