Monkeypox. Polio. Covid. A quick glance at the news on any given day seems to indicate that outbreaks, epidemics, and perhaps even pandemics are increasing in frequency.
Granted, these types of events are hardly new; from the plagues of the 5th and 13th centuries to the Spanish flu in the 20th century and SARS-CoV-2 today, they’ve been with us from time immemorial.
What appears to be different, however, is not their frequency, but their intensity, with research reinforcing that we may be facing unique challenges and smaller windows to intervene as we move forward.
Findings from a modeling study, published in 2021 in Proceedings of the National Academy of Sciences, underscore that without effective intervention, the probability of extreme events like COVID-19 will likely increase threefold in the coming decades.
Amesh Adalja, MD, senior scholar, Johns Hopkins Center for Health Security, Baltimore, told this news organization.
“It’s all been based on some unusual cluster of cases that were causing severe disease and overwhelming local authorities. So often, like Indiana Jones, somebody got dispatched to deal with an outbreak,” Dr. Adalja said.
In a perfect post-COVID world, government bodies, scientists, clinicians, and others would cross silos to coordinate pandemic prevention, not just preparedness. The public would trust those who carry the title “public health” in their daily responsibilities, and in turn, public health experts would get back to their core responsibility – infectious disease preparedness – the role they were initially assigned following Europe’s Black Death during the 14th century. Instead, the world finds itself at a crossroads, with emerging and reemerging infectious disease outbreaks that on the surface appear to arise haphazardly but in reality are the result of decades of reaction and containment policies aimed at putting out fires, not addressing their cause.
Dr. Adalja noted that only when the threat of biological weapons became a reality in the mid-2000s was there a realization that economies of scale could be exploited by merging interests and efforts to develop health security medical countermeasures. For example, it encouraged governments to more closely integrate agencies like the Biomedical Advanced Research and Development Authority and infectious disease research organizations and individuals.
Still, while significant strides have been made in certain areas, the ongoing COVID-19 pandemic has revealed substantial weaknesses remaining in public and private health systems, as well as major gaps in infectious disease preparedness.
The role of spillover events
No matter whom you ask, scientists, public health and conservation experts, and infectious disease clinicians all point to one of the most important threats to human health. As Walt Kelly’s Pogo famously put it, “We have met the enemy, and he is us.”
“The reason why these outbreaks of novel infectious diseases are increasingly occurring is because of human-driven environmental change, particularly land use, unsafe practices when raising farmed animals, and commercial wildlife markets,” Neil M. Vora, MD, a physician specializing in pandemic prevention at Conservation International and a former Centers for Disease Control and Prevention epidemic intelligence officer, said in an interview.
In fact, more than 60% of emerging infections and diseases are due to these “spillover events” (zoonotic spillover) that occur when pathogens that commonly circulate in wildlife jump over to new, human hosts.
Several examples come to mind.
COVID-19 may have begun as an enzootic virus from two undetermined animals, using the Huanan Seafood Market as a possible intermediate reservoir, according to a July 26 preprint in the journal Science.
Likewise, while the Ebola virus was originally attributed to deforestation efforts to create palm oil (which allowed fruit bat carriers to transfer the virus to humans), recent research suggests that bats dwelling in the walls of human dwellings and hospitals are responsible for the 2018 outbreak in the Democratic Republic of Congo.
(Incidentally, just this week, a new Ebola case was confirmed in Eastern Congo, and it has been genetically linked to the previous outbreak, despite that outbreak having been declared over in early July.)
“When we clear forests, we create opportunities for humans to live alongside the forest edge and displace wildlife. There’s evidence that shows when [these] biodiverse areas are cleared, specialist species that evolved to live in the forests first start to disappear, whereas generalist species – rodents and bats – continue to survive and are able to carry pathogens that can be passed on to humans,” Dr. Vora explained.
So far, China’s outbreak of the novel Langya henipavirus is believed to have spread (either directly or indirectly) by rodents and shrews, according to reports from public health authorities like the European Centre for Disease Prevention and Control, which is currently monitoring the situation.
Yet, an overreliance on surveillance and containment only perpetuates what Dr. Vora says are cycles of panic and neglect.
“We saw it with Ebola in 2015, in 2016 to 2017 with Zika, you see it with tuberculosis, with sexually transmitted infections, and with COVID. You have policymakers working on solutions, and once they think that they’ve fixed the problem, they’re going to move on to the next crisis.”
It’s also a question of equity.
Reports detailing the reemergence of monkeypox in Nigeria in 2017 were largely ignored, despite the fact that the United States assisted in diagnosing an early case in an 11-year-old boy. At the time, it was clear that the virus was spreading by human-to-human transmission versus animal-to-human transmission, something that had not been seen previously.
“The current model [is] waiting for pathogens to spill over and then [continuing] to spread signals that rich countries are tolerant of these outbreaks so long as they don’t grow into epidemics or pandemics,” Dr. Vora said.
This model is clearly broken; roughly 5 years after Nigeria reported the resurgence of monkeypox, the United States has more than 14,000 confirmed cases, which represents more than a quarter of the total number of cases reported worldwide.