Is a New Pandemic on the Horizon? Key Factors to Consider

New infectious diseases continue to emerge, raising concerns about another global pandemic. Climate change, urbanization, and increased human-wildlife interaction create opportunities for pathogens to spread. Scientists monitor these risks to anticipate and prevent outbreaks.

Understanding the key drivers of disease emergence is essential in assessing pandemic threats.

Viral Threats With High Outbreak Potential

Novel viruses capable of causing widespread outbreaks remain a major concern. Zoonotic spillover events, where viruses jump from animals to humans, have led to some of history’s most devastating pandemics, including HIV, influenza, and SARS-CoV-2. These events are increasing due to habitat destruction, wildlife trade, and agricultural expansion, which bring humans into closer contact with previously isolated viral reservoirs. Bats, rodents, and primates are significant hosts, harboring viruses with pandemic potential, including coronaviruses, filoviruses, and paramyxoviruses.

Coronaviruses remain a pressing threat. SARS-CoV-2 demonstrated how rapidly a novel coronavirus can spread, and related viruses such as SARS-CoV and MERS-CoV have exhibited high mortality rates. Surveillance efforts have identified numerous SARS-like coronaviruses in bats, some with genetic features that could enable human transmission. A Nature Medicine (2023) study highlighted the potential for recombination between different coronaviruses, which could generate variants with enhanced infectivity or immune evasion.

Filoviruses such as Ebola and Marburg virus remain concerning due to their high fatality rates and potential for human-to-human transmission. The 2014-2016 West African Ebola outbreak showed how urban transmission can amplify spread, overwhelming healthcare systems. A Lancet Infectious Diseases (2024) study identified new Ebola strains with mutations that may influence transmissibility, emphasizing the need for continued genomic surveillance.

Influenza viruses also pose a persistent pandemic threat, particularly avian strains such as H5N1 and H7N9. These viruses have caused sporadic human infections with high mortality rates, and concerns remain about their potential to acquire mutations enabling sustained human-to-human transmission. The WHO classifies certain avian influenza strains as having “high pandemic potential.” A 2024 Science study examined genetic changes in H5N1 that could enhance its ability to bind to human respiratory receptors, a key factor in transmissibility.

Bacterial Adaptations Driving Rapid Spread

Bacteria evolve mechanisms that enhance their transmission and persistence, accelerating disease spread. One of the most concerning factors is the rapid acquisition of antibiotic resistance, which allows bacterial pathogens to survive treatments that once controlled them. Horizontal gene transfer, particularly through plasmids and transposons, spreads resistance genes between bacterial populations. A Nature Microbiology (2023) study found multidrug resistance genes increasingly present in environmental reservoirs, including wastewater and agricultural runoff, providing a continuous source of resistant bacteria.

Beyond resistance, bacteria employ structural adaptations that facilitate dissemination. Biofilm formation, in which bacterial communities encase themselves in a protective matrix, enhances survival on surfaces and medical devices, increasing the risk of healthcare-associated infections. Pseudomonas aeruginosa and Staphylococcus aureus are notorious for biofilm-mediated persistence, complicating eradication efforts. Research in The Lancet Microbe (2024) highlighted how biofilm-associated infections lead to prolonged disease courses, as embedded bacteria exhibit up to 1,000 times greater resistance to antimicrobials compared to their planktonic counterparts.

Respiratory bacteria such as Streptococcus pneumoniae and Bordetella pertussis have evolved mechanisms to enhance airborne dissemination. A 2024 Cell Host & Microbe investigation uncovered genetic mutations in Mycobacterium tuberculosis that increase aerosol stability, extending the time viable bacteria can remain suspended in air. This adaptation lengthens transmission windows, making containment more challenging in densely populated areas.

Environmental persistence further amplifies bacterial spread. Vibrio cholerae, the causative agent of cholera, can enter a dormant state known as viable but non-culturable (VBNC), allowing it to persist in aquatic environments before reactivating under favorable conditions. A mBio (2023) study identified genetic regulators that control this transition, showing how bacterial pathogens can evade detection and resurface unpredictably. This complicates outbreak prediction and underscores the need for continuous environmental monitoring.

Emerging Fungal Species In Unstable Ecosystems

Fungal pathogens are an increasing threat as shifting climates create new opportunities for their emergence and spread. Changes in temperature, humidity, and soil composition are altering fungal distributions, allowing species to thrive in new regions. Candida auris, a multidrug-resistant yeast, has spread globally since its identification in 2009. Researchers link its emergence to rising global temperatures, which may have facilitated its adaptation to human body temperature—a trait uncommon among environmental fungi.

Ecosystem disruptions are also driving fungal proliferation by altering host-pathogen dynamics. Deforestation, agricultural expansion, and urban encroachment disturb soil microbiomes, enabling opportunistic fungi to expand their range. Coccidioides species, responsible for Valley fever, have spread beyond their historical range in the southwestern U.S., with cases now appearing in previously unaffected states. This expansion is linked to soil disturbances and prolonged drought conditions that favor fungal spore dispersal. Similarly, Histoplasma and Blastomyces have been detected in new areas, raising concerns about their increasing prevalence.

Fungal resistance to antifungal treatments further complicates management. Unlike bacterial pathogens, fungi have fewer available antifungal drugs, making resistance particularly concerning. The widespread use of azole fungicides in agriculture has contributed to the rise of azole-resistant Aspergillus fumigatus infections. Studies show resistant strains are now commonly found in the environment, suggesting agricultural fungicide use is exerting selective pressure on fungal populations. This resistance threatens first-line antifungal treatments, necessitating stricter regulations on fungicide application.

Parasitic Organisms Surviving In Changing Climates

Rising global temperatures and shifting precipitation patterns are reshaping the distribution and resilience of parasitic organisms. Warmer winters and longer growing seasons have extended the active periods of many vectors, such as mosquitoes and ticks, which transmit parasitic diseases. Malaria, caused by Plasmodium species, has begun appearing at higher altitudes in regions like the Ethiopian Highlands, where cooler temperatures historically limited mosquito survival. Similarly, tick-borne parasites like Babesia microti, responsible for babesiosis, are expanding northward in North America, aided by milder winters.

Climatic shifts influence parasite life cycles, often accelerating transmission. Increased humidity and rainfall create ideal breeding conditions for waterborne parasites like Schistosoma species, which rely on freshwater snails as intermediate hosts. Erratic flooding expands these snail habitats, leading to higher infection rates. Extreme weather events, such as hurricanes and monsoons, further exacerbate disease spread by contaminating drinking water sources with parasitic cysts from Giardia and Cryptosporidium, increasing outbreak risks.

Infectious Disease Clusters From Urbanization

Rapid urban expansion intensifies conditions that facilitate infectious disease outbreaks. High population densities and inadequate infrastructure create environments where pathogens spread easily. Overcrowded housing, poor sanitation, and limited healthcare access contribute to diseases such as tuberculosis, dengue fever, and leptospirosis. Informal settlements, often lacking clean water and waste management, become breeding grounds for waterborne and vector-borne infections. A Lancet Global Health (2023) study found that urban slums in Southeast Asia had significantly higher dengue infection rates than rural areas, largely due to standing water accumulation and insufficient mosquito control.

Mass transportation accelerates disease spread by allowing pathogens to move quickly across regions. Subways, buses, and air travel create high-contact environments where respiratory infections, including influenza and COVID-19, propagate efficiently. Research in Nature Communications (2024) analyzed viral transmission in public transit systems and found that high-touch surfaces, such as handrails and ticket machines, harbored viable virus particles for extended periods. Addressing these vulnerabilities through improved sanitation, vector control, and public health interventions will be essential in mitigating large-scale outbreaks.

Role Of Wildlife In Pathogen Emergence

Human encroachment into wildlife habitats has significantly increased the likelihood of novel pathogen spillover events. Deforestation, agriculture, and trade bring humans into close contact with wild animal reservoirs. Many emerging infectious diseases originate from zoonotic sources, with viruses, bacteria, and fungi adapting to human hosts following repeated exposure. The illegal wildlife trade has been implicated in the transmission of several high-profile pathogens, including SARS-CoV and Nipah virus. A World Organisation for Animal Health (2023) report emphasized that unregulated wildlife markets remain a persistent risk factor for zoonotic disease emergence.

Changes in animal migration patterns due to habitat loss and climate shifts further contribute to disease emergence. Bats, known reservoirs for viruses such as Ebola and coronaviruses, are increasingly forced into proximity with human populations. Monitoring wildlife health and implementing conservation strategies to preserve natural habitats may help reduce spillover events, ultimately lowering pandemic risks.