Why outbreaks of infectious diseases are becoming so common

SARS-CoV-2. Monkey pox. polio. Marburg. These viruses are no longer only familiar to public health experts, but household names around the world thanks to their recent infiltration into human populations. Humans have always encountered pathogens of all kinds, but attacks are becoming more common and more intense than ever.

“We are moving into an era of epidemics and pandemics, and they will be more complex and more frequent,” says Jeremy Farrar, director of Wellcome, a global health charity that addresses health challenges. “We tend to see everybody [outbreak] on its own, as a separate episode. But the truth is that almost all of them are symptomatic of underlying drivers, all of which are part of 21st century life.

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

The explanation lies in the gathering perfect storm of factors that interfere with almost every way we live our modern lives, from the ubiquity of world travel to the deeper penetration of humans into previously untouched natural habitats and the modernization that has brought to climate change, urbanization, and overpopulation. Even the immediate and unfiltered way we communicate on social media contributes, as misinformation is often shared, believed and elevated to the same degree as credible messages. Then there is mercury and an increasingly unstable balance of geopolitics that has driven millions from their homes into refugee camps and migrant housing that are breeding grounds for infectious diseases.

Simply put, the many infectious diseases facing the world today are “simply the evolution of microbes and humans colliding,” says Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

Read more: A hotter world means more outbreaks of disease in our future

This interface is more common as people move closer to nature. Coronaviruses, for example, live in bats, while influenza viruses inhabit bird populations; both viruses spread wherever animals roam, which increasingly includes regions where they come into contact with humans.

Deforestation, climate change and urbanization make such interactions more likely. In the case of Ebola, experts say, the largest outbreak of the disease in West Africa in 2014 was likely fueled by the fact that urbanization concentrated more people in densely populated cities than was the case when the virus was first reported in humans in the 1970s. “In the 1990s and 2000s, Ebola did not change; what changed was that Ebola was a disease that was spreading in rural areas, that had affected isolated villages but had not reached the big urban centers,” Osterholm says. Urbanization and overcrowding in big cities, where sanitation and social distancing are not always practiced, mean that viruses and bacteria find it easier to seek out new hosts.

Improvements in travel also come with urbanization. And air travel doesn’t just transport people; it also carries whatever viruses and bacteria are hiding in other parts of the world in a matter of hours. The recent monkeypox epidemic which distribution to 94 countries in three months, is one example. The virus, which is endemic to central and west Africa, has taken 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 a real global challenge because transport was so slow and incomplete that it wouldn’t have spread the way modern air transport can,” Osterholm says. .


There may be another powerful force that makes such human-pathogen confrontations more significant and even more deadly. Viruses and other microbes are not separate agents of disease, but exist as a dynamic and ever-evolving community. Every human encounter is a chance for pathogens like viruses to become fitter and more adept at infecting and causing disease in humans. This is likely the case with coronaviruses; SARS and MERS, for example, cause infections with high mortality rates, but are not transmitted very efficiently from person to person. However, the next-generation virus SARS-CoV-2 has finally found a way to spread easily from one human host to another.

Something similar can happen with monkeypox. American scientists working with their colleagues in Nigeria, where the virus is endemic, began to see changes in the virus several years ago. “They saw that the virus was more efficient at transmitting the disease from person to person,” said Dr. Raj Panjabi, senior director for global security and biosecurity at the White House National Security Council. “This is a wake-up call. It signals that perhaps transmission has changed because the virus has adapted better to [live] among us.” Farrar notes that with each previous monkeypox outbreak in Africa, the chain of infection — one person infecting another — gradually lengthens, “and the infections last longer,” he says. “Instead of one or two infected, now it’s five to six people, then 10 to 12 people.”

Osterholm says all these converging factors put the world in a dangerous place. “Each of these is a public health problem in and of itself,” he says. “Add them all together and you have a crisis.”

Do people have a chance? “I think we’re the most vulnerable we’ve ever been in my professional career,” Farrar says. He sees the greatest threat to humans’ ability to prevent major pandemics coming from our inability to collaborate, share public health information, and build effective defenses against infectious diseases. “Biodiversity, land use, habitat protection and social media aside, the biggest challenge is geopolitics,” he says, citing aggression in Eastern Europe, East-West tensions and the disparity of health resources and health infrastructure between developed and developing countries. states. “Unless we resolve geopolitical issues, then I fear we will not see what emerges from China, Europe, Africa, the Americas and Southeast Asia. We must return to the understanding that the world is very small and we are interconnected.

Read more: Virus hunters are trying to prepare for the next pandemic

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

But developed countries must lead by example. The US is making some strides; President Biden revived the Global Health Security and Biodefense Directorate, which Panjabi heads, after it was disbanded during the Trump administration. Biden proposed a record investment of $88 billion to prepare the country for the next pandemic threat, spread over five years, which would prioritize investment in testing, vaccine and treatment research, as well as surveillance for new diseases and building supplies of personal protective equipment and trained health workers that can be deployed during a public health emergency. “Never before has so much money been requested for pandemic preparedness and global health security,” says Panjabi.

Securing this money will be a huge challenge. But such an 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 the National Institutes of Public Health — not just in the U.S. but around the world — the better prepared we will be,” Panjabi says. “These investments are aimed at achieving 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 the growing production to rapidly meet global needs.”

Rapid and effective response will have to become routine if we are to withstand the onslaught of outbreaks that are sure to come our way. “Microbial evolution is alive and well,” Osterholm says. “We are fighting an enemy that is growing and changing every day to accommodate the changes in the world.”

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