The world has long battled invisible enemies—viruses and pathogens that emerge without warning, disrupting lives and claiming millions. While humanity has made remarkable strides in medicine, the shadows of past pandemics remind us how quickly our progress can be tested. The most unnerving aspect? The next threat may already be lurking, unseen and unpredictable, waiting for the perfect moment to strike.

In a time when zoonotic spillovers are on the rise, and climate change reshapes ecosystems, the possibility of another devastating outbreak feels less like a distant worry and more like an inevitability. Could it be an evolution of a familiar foe or an entirely new menace? The answers may lie in the emerging diseases scientists are racing to understand—each with the potential to reshape the course of history.

1. Coronavirus

The next pandemic could once again be driven by a coronavirus. Past outbreaks such as Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS) have demonstrated the ability of coronaviruses to jump from animals to humans, causing significant public health crises. The World Health Organization (WHO) has consistently emphasized the ongoing risk of these zoonotic viruses, underscoring the need for vigilance and preparedness.

COVID-19, caused by the SARS-CoV-2 virus, remains an active global health challenge. While some countries have relaxed reporting and surveillance measures, the virus continues to circulate widely. Wastewater surveillance data reveals infection rates that far exceed official counts, indicating the persistence of the pandemic.

2. Crimean-Congo Hemorrhagic Fever

Crimean-Congo Hemorrhagic Fever (CCHF) is a tick-borne viral disease that poses a significant threat to global health, with the potential to incite the next pandemic. The World Health Organization (WHO) has identified CCHF as a priority pathogen due to its high fatality rate and expanding geographic range.

CCHF is primarily transmitted to humans through bites from infected Hyalomma ticks or via direct contact with the blood or tissues of infected livestock, such as cattle, sheep, and goats. Human-to-human transmission can also occur through exposure to infectious blood or bodily fluids. 

The disease manifests suddenly with symptoms including high fever, muscle aches, dizziness, neck pain, backache, headache, sore eyes, and photophobia. As the illness progresses, severe symptoms such as large areas of severe bruising, severe nosebleeds, and uncontrolled bleeding at injection sites can occur, leading to a case fatality rate of up to 40%. 

Climate change plays a role in the spread of CCHF. Rising temperatures and altered precipitation patterns have expanded the habitat of Hyalomma ticks into new regions, including parts of Europe. A study in PLOS Neglected Tropical Diseases discusses the establishment of Hyalomma marginatum ticks in southern France and the concurrent appearance of CCHF cases in neighboring Spain, indicating the disease’s northward expansion. Another study conducted in Iran found a strong association between meteorological factors and the occurrence of CCHF, further suggesting that climate change could lead to increased outbreaks. 

3. Paramyxoviruses

Paramyxoviruses, a diverse family of single-stranded RNA viruses, have long been associated with human diseases such as measles and mumps. However, emerging members like the Nipah and Hendra viruses have raised significant concerns due to their high fatality rates and potential to cause the next pandemic.

A significant concern with paramyxoviruses is their zoonotic potential—the ability to jump from animals to humans. Bats, particularly fruit bats of the genus Pteropus, serve as natural reservoirs for henipaviruses. Spillover events often occur when humans come into contact with infected animals or their secretions. For instance, the Nipah virus has been transmitted to humans through the consumption of contaminated date palm sap and direct contact with infected pigs.

Human-to-human transmission has also been documented, notably with the Nipah virus in Bangladesh and India, where person-to-person spread has been observed in healthcare settings. This capability raises concerns about the potential for wider outbreaks.

4. Influenza

Influenza, commonly known as the flu, is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs. While often perceived as a routine seasonal ailment, influenza has a notorious history of evolving into pandemics with devastating global impacts. 

• The 1918–1919 Pandemic (H1N1): Known as the “Spanish Flu,” this pandemic infected approximately one-third of the global population, resulting in an estimated 50 million deaths.
  
• The 1957–1958 Pandemic (H2N2): Referred to as the “Asian Flu,” it caused about 1.1 million deaths worldwide.
   
• The 1968–1969 Pandemic (H3N2): Known as the “Hong Kong Flu,” this pandemic led to approximately 1 million deaths globally.

Avian influenza, or “bird flu,” primarily affects bird species but has the potential to infect humans. The highly pathogenic avian influenza A (H5N1) virus is of particular concern due to its high mortality rate in humans and its ability to infect a broad range of hosts.

Human infections with avian influenza viruses can occur through direct contact with infected birds or contaminated environments. Activities such as slaughtering, defeathering, and handling carcasses of infected poultry are high-risk behaviors. While human-to-human transmission is rare, the possibility exists, especially in cases of close and prolonged contact.

5. Rift Valley Fever

Rift Valley Fever (RVF) is a viral zoonosis that primarily affects animals but can also infect humans. Transmitted by mosquitoes and other blood-feeding insects, RVF poses significant health risks, particularly in regions where humans and livestock interact closely. 

Humans typically contract RVF through direct contact with the blood, body fluids, or tissues of infected animals during activities such as slaughtering, butchering, or veterinary procedures. Consuming unpasteurized or uncooked milk from infected animals also poses a risk. Occupational groups like herders, farmers, and slaughterhouse workers are particularly vulnerable.

RVF is also transmitted to humans through bites from infected mosquitoes, primarily Aedes species. These mosquitoes can acquire the virus from feeding on infected animals and subsequently transmit it to humans.

Climate change significantly influences the epidemiology of RVF. Increased rainfall and flooding create favorable breeding conditions for mosquito vectors, leading to higher transmission rates. A study in East Africa, published in BMJ Global Health, observed that climate variability, including changes in temperature and precipitation, expanded the geographic range of RVF outbreaks.

Additionally, warmer temperatures can accelerate the life cycle of mosquitoes, enhancing their capacity to transmit the virus. The Centers for Disease Control and Prevention (CDC) notes that climate change affects the spread of vector-borne diseases, including RVF, by altering vector distribution and abundance.

6. Zika Virus

Zika virus, primarily transmitted by Aedes mosquitoes, has emerged as a significant global health concern due to its rapid spread and severe health implications, particularly for pregnant women and their infants.

The primary mode of Zika virus transmission is through the bite of infected Aedes mosquitoes, notably Aedes aegypti. These mosquitoes are aggressive daytime biters but can also bite at night. The virus can also be spread through sexual contact with an infected person, even if they are asymptomatic. Pregnant women can also transmit the virus to the fetus, leading to congenital infections

The incubation period for Zika virus disease is estimated to be 3–14 days. Many infected individuals remain asymptomatic; however, when symptoms do occur, they are generally mild and last for 2–7 days. Common symptoms include fever, rash, conjunctivitis, muscle and joint pain, headache, and malaise.

Since its identification in Uganda in 1947, Zika virus has spread across Africa, Asia, the Americas, and the Pacific. As of 2022, 89 countries and territories have reported evidence of mosquito-borne Zika virus transmission.

7. Lassa Fever

Lassa fever is an acute viral hemorrhagic illness endemic to parts of West Africa, notably Nigeria, Liberia, Sierra Leone, and Guinea. Transmitted primarily through contact with the urine or feces of infected Mastomys rats, Lassa fever poses significant health risks, especially in regions with high rodent populations and limited healthcare infrastructure. 

Humans typically contract Lassa fever through exposure to food or household items contaminated with the urine or feces of infected Mastomys rats. These rodents are common in West Africa and often live in close proximity to human dwellings.

The incubation period for Lassa fever ranges from 6 to 21 days. Approximately 80% of infections are mild or asymptomatic; however, severe cases can present with fever, headache, vomiting and diarrhea, facial swelling, chest pain, neurological issues, and bleeding from gums, eyes, or nose. In severe cases, multi-organ failure can occur.

In October 2024, a suspected case of Lassa fever was reported in Iowa, USA, involving an individual who had recently traveled to West Africa. This incident highlights the potential for Lassa fever to spread beyond its traditional endemic regions. 

8. Disease X

The term “Disease X” serves as a placeholder adopted by the World Health Organization (WHO) to represent a hypothetical, unknown pathogen that could cause a future epidemic or pandemic. This concept underscores the necessity for proactive preparedness against emerging infectious threats.

In 2018, the WHO introduced “Disease X” into its list of priority pathogens to acknowledge the potential emergence of an unforeseen infectious agent capable of causing significant public health emergencies. Factors such as increased human-animal interactions, global travel, urbanization, and ecological changes heighten the risk of novel pathogens emerging and spreading rapidly.

The COVID-19 pandemic exemplifies the realization of Disease X, as SARS-CoV-2 was an unknown virus that led to a global health crisis. This experience highlights the critical need for ongoing surveillance, research, and investment in public health infrastructure to mitigate the impact of future pandemics. 

My Personal RX on Staying Healthy Amid Emerging Threats

As a doctor, I always advocate for practical, sustainable habits that empower individuals to protect their health proactively. With the rise of emerging health threats, building resilience is more important than ever. Here are my personal recommendations to strengthen your body and mind against the unexpected:

1. Prioritize a Strong Immune System: Your immune system is your first defense. Incorporate a targeted blend of nutrients like those found in my Immune Support to ensure your body’s immune reserves are always ready.
2. Stay Active Daily: Regular exercise improves circulation, boosts immunity, and reduces stress—a trifecta for keeping your body prepared to fight infections.
3. Understand the Gut-Brain Connection: Your gut plays a central role in overall health. Delve into resources like my book Heal Your Gut, Save Your Brain to learn how to optimize your gut health and, in turn, enhance your mental well-being.
4. Get Quality Sleep: Aim for 7-9 hours of restorative sleep each night. It’s during sleep that your body repairs and fortifies its defenses.
5. Adopt Mindful Nutrition: Incorporate a variety of fruits, vegetables, lean proteins, and whole grains into your diet. Consider fermented foods to nurture a healthy gut microbiome.
6. Wash Your Hands Regularly: This simple habit can prevent a multitude of infections. Keep hand sanitizer on hand for times when soap and water aren’t available.
7. Stay Hydrated: Proper hydration supports cellular functions and overall vitality, making it an essential yet often overlooked habit.
8. Stay Informed and Proactive: Keep up with credible health advisories and recommendations to stay ahead of potential risks.
9. Create a Calming Routine: Chronic stress weakens your immune system. Incorporate practices like yoga, meditation, or deep breathing to maintain balance.
10. Prepare Your Mind and Body Holistically: Equip yourself with tools, knowledge, and support to stay resilient against the unknown. A proactive, informed approach is the best form of self-care.

Sources:

1. Prioritizing diseases for research and development in emergency contexts. (n.d.). https://www.who.int/activities/prioritizing-diseases-for-research-and-development-in-emergency-contexts
2. Neumann, G., & Kawaoka, Y. (2023). Which virus will cause the next pandemic? Viruses, 15(1), 199. https://doi.org/10.3390/v15010199
3. World Health Organization: WHO. (2022, May 23). Crimean-Congo haemorrhagic fever. https://www.who.int/news-room/fact-sheets/detail/crimean-congo-haemorrhagic-fever
4. Khan, S., Akbar, S. M. F., Mahtab, M. A., Uddin, M. N., Rashid, M. M., Yahiro, T., Hashimoto, T., Kimitsuki, K., & Nishizono, A. (2024). Twenty-Five years of Nipah outbreaks in Southeast Asia: a persistence threat to global health. IJID Regions, 13, 100434. https://doi.org/10.1016/j.ijregi.2024.100434
5. Situma, S., Nyakarahuka, L., Omondi, E., Mureithi, M., Mweu, M. M., Muturi, M., Mwatondo, A., Dawa, J., Konongoi, L., Khamadi, S., Clancey, E., Lofgren, E., Osoro, E., Ngere, I., Breiman, R. F., Bakamutumaho, B., Muruta, A., Gachohi, J., Oyola, S. O., . . . Singh, D. (2024). Widening geographic range of Rift Valley fever disease clusters associated with climate change in East Africa. BMJ Global Health, 9(6), e014737. https://doi.org/10.1136/bmjgh-2023-014737
6. Vector-Borne diseases. (2024, March 2). Climate and Health. https://www.cdc.gov/climate-health/php/effects/vectors.html
7. World Health Organization: WHO. (2022b, December 8). Zika virus. https://www.who.int/news-room/fact-sheets/detail/zika-virus
8. World Health Organization: WHO. (2024, December 5). Lassa fever. https://www.who.int/news-room/fact-sheets/detail/lassa-fever
9. Lassa Fever Suspected in Death of U.S. Traveler Returning from West Africa. (n.d.). CDC Newsroom. https://www.cdc.gov/media/releases/2024/s1028-lassa-fever.html
10. Research response to pathogen X during a pandemic. (2024, January 19). https://www.who.int/news-room/events/detail/2024/01/19/default-calendar/Research-response-to-pathogen-X-during-a-pandemic
11. Tahir, M. J., Sawal, I., Essar, M. Y., Jabbar, A., Ullah, I., & Ahmed, A. (2021). Disease X: A hidden but inevitable creeping danger. Infection Control and Hospital Epidemiology, 43(11), 1758–1759. https://doi.org/10.1017/ice.2021.342