Another pandemic is not a matter of “if” but “when.” That’s the consistent assessment from the World Health Organization, the CDC, and infectious disease experts worldwide. The timing and severity are impossible to predict, but the biological and environmental conditions that produce pandemics are intensifying, not fading. Several specific threats are already on the radar, and global preparedness has improved since COVID-19, though significant gaps remain.
Why Experts Say It’s Inevitable
Pandemics are a recurring feature of human history, not rare anomalies. New infectious diseases have emerged at an accelerating pace over the past several decades, and the underlying forces driving that trend are getting stronger. Habitat destruction, urbanization, deforestation, and wildlife trade all push humans and animals into closer contact, creating more opportunities for viruses to jump species. When ecosystems fragment, the animal species that thrive tend to be the ones already adapted to living near people, like rats, bats, and certain birds, which increases the chance of a virus making the leap.
Climate change compounds the problem. Rising temperatures expand the geographic range of mosquitoes and other disease-carrying organisms, exposing new populations to infections they’ve never encountered. Warmer conditions also speed up how fast pathogens and their carriers reproduce. Meanwhile, environmental stress weakens wildlife immune systems, causing animals to shed more viruses into the environment. Biodiversity loss removes a natural buffer: diverse ecosystems dilute pathogen spread, so as species disappear, infection pressure on humans rises.
The Threats Being Watched Right Now
The WHO maintains a priority list of diseases with the highest pandemic potential. It currently includes COVID-19, Ebola, Marburg virus disease, Lassa fever, MERS, SARS, Nipah virus, Crimean-Congo hemorrhagic fever, Rift Valley fever, and Zika. The list also includes something called “Disease X,” a placeholder representing a pathogen that doesn’t yet cause human disease but could trigger a serious international outbreak. The concept exists specifically to force researchers and governments to prepare for the unknown, not just the familiar.
The most closely watched threat right now is H5N1 bird flu. Since 1997, more than 970 human infections have been reported across 24 countries. The United States has been dealing with an ongoing outbreak tied to infected animals: as of the end of 2024, the CDC had monitored over 10,600 people exposed to infected animals, tested more than 540, and confirmed 63 cases. The critical detail is that human-to-human transmission has not been identified in the U.S., and the last confirmed instance of even limited, non-sustained person-to-person spread anywhere in the world was in 2007. The CDC is also not seeing genetic changes in the virus that would help it infect humans more easily. That’s reassuring for now, but influenza viruses mutate constantly, which is why surveillance remains so intense.
The Slow-Burning Crisis of Drug Resistance
Not every pandemic threat comes from a novel virus. Antimicrobial resistance, where bacteria evolve to survive the drugs designed to kill them, is a growing emergency that could reshape infectious disease in the coming decades. A 2024 analysis published in The Lancet projects that by 2050, drug-resistant bacterial infections could directly kill an estimated 1.91 million people per year and play a role in 8.22 million annual deaths globally. For context, an earlier landmark estimate in 2014 warned of 10 million deaths per year from this problem, a figure that helped place drug resistance among the most serious health threats of the century.
Drug resistance doesn’t look like a traditional pandemic with a single explosive outbreak, but it erodes the foundation that modern medicine depends on. Routine surgeries, cancer treatment, and organ transplants all rely on antibiotics working. As more infections become untreatable, the toll compounds steadily rather than arriving in a single wave.
How Preparedness Has Changed
The COVID-19 pandemic exposed enormous weaknesses in global response systems, but it also accelerated investments in early detection and faster countermeasures. One of the most significant advances is wastewater surveillance. By testing sewage for viral genetic material, public health agencies can detect outbreaks before people show up at clinics. In a study of long-term care facilities, wastewater testing detected outbreaks ahead of clinical testing in about 60% of confirmed cases, and a negative wastewater result reliably predicted that no outbreak was brewing. This approach is now being expanded to track influenza, bird flu, and other pathogens in communities across the U.S. and Europe.
On the vaccine front, an international initiative called the 100 Days Mission aims to develop a new vaccine against a future pandemic pathogen within 100 days of that threat being recognized. The goal depends on continued investment in manufacturing capacity, health systems, and equitable global distribution. Platform technologies like mRNA, which proved their speed during COVID-19, are central to this effort. Pharmaceutical companies, government agencies, and international organizations are all investing in the ability to rapidly adapt these platforms to new targets.
The concept of Disease X is itself a preparedness tool. Rather than waiting for an unknown virus to emerge and then scrambling, researchers are proactively studying entire viral families, mapping how they transmit, how they affect the human body, and what immune responses matter. This work involves every level of the public health system, from the WHO and the CDC down to state health departments and individual hospitals, as well as pharmaceutical companies developing flexible vaccine technologies.
The Pandemic Agreement
In May 2025, WHO member states adopted a landmark legal instrument called the WHO Pandemic Agreement, designed to strengthen prevention, preparedness, and response globally. A central pillar is a system for sharing pathogen samples and genetic sequences rapidly across borders, paired with a commitment to share the benefits (vaccines, treatments, diagnostics) fairly and equitably based on public health need. The agreement also establishes a global supply chain network coordinated by the WHO to distribute pandemic health products quickly, along with a financial mechanism to help countries build their preparedness capacity.
The agreement isn’t fully operational yet. An intergovernmental working group is still negotiating the details of the pathogen-sharing system, and once that piece is finalized, 60 countries need to formally ratify the agreement before it takes legal effect. The political will to complete this process will be tested by competing national interests, but the framework represents the most ambitious attempt at coordinated pandemic governance since the International Health Regulations were updated in 2005.
What This Means Practically
The honest answer is that another pandemic will happen, but no one can tell you when or what pathogen will cause it. It could be a mutated strain of bird flu, a virus jumping from wildlife in a deforested region, or something entirely unexpected. The gap between detection and global spread has narrowed as international travel makes it possible for a new pathogen to reach multiple continents within days.
What has genuinely improved is the speed at which the world can identify and respond to threats. Wastewater monitoring provides earlier warnings. Vaccine platforms can be adapted in weeks rather than years. Genomic sequencing can characterize a new virus within days of its discovery. These tools don’t prevent pandemics, but they compress the timeline between emergence and response, which directly determines how many people get sick and how severely.
The factors pushing toward the next pandemic, including habitat destruction, climate change, global travel, and antimicrobial resistance, are not slowing down. Preparedness has improved, but it remains uneven across countries. The question isn’t whether another pandemic is coming. It’s whether the systems built since COVID-19 will hold up when it does.