Which Diseases Pose The Biggest Risks In The Future?

In our increasingly interconnected world, the question of which diseases will dominate future health concerns has become both urgent and complex.

As climate change expands the habitats of disease-carrying organisms, and global travel accelerates the spread of pathogens, the emergence of new diseases and the resurgence of old ones seem inevitable. Some of these threats may come from viruses we’ve only recently encountered, while others are familiar foes reemerging with greater resilience, like antibiotic-resistant bacteria or strains of influenza with pandemic potential.

In this article we’ll consider which diseases are most at risk of resurgence, and highlight where we’re starting to see new cases emerge.

Diseases that pose the greatest global health risk

• Rabies
• Malaria
• Depression
• SARS
• Ebola
• Gonorrhoea
• Lyme disease
• E. coli
• Hantavirus
• Dengue fever
• West Nile virus
• Tuberculosis
• Cholera
• Pertussis (whooping cough)
• Influenza
• Pneumonia

Rabies

Deaths per year: 59,000

Rabies is a deadly viral infection that affects the central nervous system of mammals, including humans. Caused by the lyssavirus rabies, it is typically transmitted through the saliva of infected animals, mainly via bites. Dogs are responsible for 99% of human rabies cases, but other carriers include bats, raccoons, skunks, and foxes.

Once symptoms appear, rabies is 100% fatal, highlighting the need for early detection and vaccination.

Initial symptoms of rabies include fever, headache, and general weakness. As the virus progresses, more severe symptoms such as anxiety, hallucinations, excessive salivation, and difficulty swallowing can develop, leading to hydrophobia (fear of water). Infected animals may exhibit behaviour changes like aggression, lethargy, or excessive drooling.

Prevention relies on mass dog vaccination, bite prevention, and prompt administration of post-exposure prophylaxis (PEP), which involves wound washing, rabies vaccination, and, if needed, rabies immunoglobulin.

Rabies remains a serious public health issue in over 150 countries, particularly in Asia and Africa, where tens of thousands of deaths occur annually. 40% of rabies victims are children under 15 years old. In the Americas, dog-mediated rabies is largely controlled, but bat-transmitted rabies has emerged as a new threat which has a higher likelihood of spreading to other regions in the coming years.

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Malaria

Deaths per year: 608,000

Malaria is a mosquito-borne infectious disease caused by Plasmodium parasites, primarily spread through the bites of infected Anopheles mosquitoes. Symptoms include fever, chills, headache, muscle aches, and fatigue, which can progress to severe complications like organ failure if not treated. Preventive measures include the use of insecticide-treated bed nets, indoor spraying, and antimalarial medications.

In 2022, there were an estimated 249 million cases of malaria worldwide, leading to 608,000 deaths across 85 countries.

The WHO African Region suffers a disproportionately high share of the global malaria burden, accounting for 94% of all cases (233 million) and 95% of all malaria deaths (580,000). Tragically, children under 5 years old are the most vulnerable, making up about 78% of malaria deaths in this region.

Despite best efforts, the fight against Malaria is far from over and the disease is currently making a significant comeback in Sub-Saharan Africa, driven by growing mosquito resistance to insecticides and parasites developing resistance to drugs.

Regions in South Asia and Southeast Asia also continue to see high transmission rates with factors such as climate change, migration, and gaps in healthcare allowing malaria to re-emerge in areas where it was previously controlled.

Depression

Deaths per year: 700,000*

Depression, or depressive disorder, is a common mental health condition characterised by persistent feelings of sadness, emptiness, or irritability, and a loss of interest in activities.

Depression affects approximately 5% of adults worldwide, with women being 50% more likely to experience it than men.

Around 280 million people globally are affected by depression, including 5.7% of adults over 60. Depression can impact all aspects of life, leading to problems in relationships, work, and daily activities, and is a major contributor to suicide, which claims over 700,000 lives each year.

The causes of depression are complex, involving a mix of social, psychological, and biological factors. Stressful life events, such as job loss, trauma, or bereavement, can increase the risk. Physical health issues, like chronic diseases, may also contribute to or exacerbate depression. 

Treatment options for depression range from cognitive behavioural therapy (CBT) to community and talking therapies. While antidepressants like SSRIs can be effective, they are not recommended for children and should be used cautiously in adolescents.

Regular physical activity, maintaining social connections, and avoiding substance abuse are recommended for both prevention and management of depression. Despite available treatments however, access remains a challenge, particularly in low- and middle-income countries, where over 75% of those affected receive no treatment due to stigma and lack of resources.

*by suicide, though not all may be caused by depression.

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SARS

Deaths per year: Unknown

Severe Acute Respiratory Syndrome (SARS) is a viral respiratory disease caused by a SARS-associated coronavirus. First identified in February 2003, it emerged in China and rapidly spread to several other countries. In late 2019, a mutation of the virus caused by SARS-CoV-2 led to the COVID-19 pandemic.

SARS is primarily transmitted through airborne droplets, similar to influenza, but can also spread via contaminated surfaces. It has an incubation period of 2–10 days, with symptoms starting as a high fever (over 38°C), often accompanied by chills, headache, muscle pain, and occasionally mild respiratory symptoms.

After 3–7 days, it may progress to a severe respiratory phase with a dry cough and difficulty breathing, requiring mechanical ventilation in 10–20% of cases. The disease primarily affects healthy adults aged 25–70, with a case fatality rate of around 3%.

In 2022, there were an estimated 249 million cases of malaria worldwide, leading to 608,000 deaths across 85 countries.

Containment relies on measures such as isolating cases, contact tracing, quarantine, and disinfection of public transport such as trains, buses and aeroplanes.

It’s also key to note that coronaviruses, like SARS-CoV, are RNA viruses which have a high rate of mutation. Future mutations may still lead to new variants that are more transmissible, show different symptoms, and evade existing immunity.

Ebola

Deaths per year: 61*

Ebola is a severe and often fatal viral haemorrhagic fever caused by the Ebola virus. It spreads through direct contact with the blood, body fluids, or tissues of infected individuals or animals.

Symptoms can appear suddenly and include fever, muscle pain, vomiting, diarrhoea, and both internal and external bleeding. The virus has an average case fatality rate of 50%, though this can vary from 25% to 90% depending on the outbreak and response.

One of the factors making Ebola an ever-present risk, is its high transmission rates. Transmission of Ebola occurs through direct contact with infected animals (such as fruit bats, chimpanzees, and gorillas) or through human-to-human contact, especially via bodily fluids.

Effective outbreak control requires rapid response, community engagement, and strict infection prevention.

Recent Ebola outbreaks have resurged in Central and West Africa, with countries like the Democratic Republic of the Congo (DRC) and Guinea seeing recurrent cases. The resurgence is partly due to challenges in containment, such as unstable healthcare systems, limited access to vaccines, and sociopolitical issues that hinder public health efforts.

*Based on 2022 data

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Gonorrhoea

Deaths per year: Unknown

Gonorrhoea is a common sexually transmitted infection caused by Neisseria gonorrhoeae, mainly spread through vaginal, oral, or anal sex. In 2020, there were an estimated 82.4 million new infections globally. 

While the infection is curable with antibiotics, rising antimicrobial resistance is making treatment more challenging. Symptoms vary by gender; many infected people show no symptoms but some may experience discharge and pain when urinating.

If left untreated, gonorrhoea can lead to severe complications including infertility and increased risk of HIV.

The prevalence of gonorrhoea is highest among vulnerable populations, including men who have sex with men, sex workers, and adolescents. Complications can affect various body parts: pelvic inflammatory disease and ectopic pregnancies in women, scrotal swelling in men, and eye infections in newborns. Rarely, the infection can spread throughout the body, causing fever and affecting organs such as the skin, heart, and joints.

Preventing gonorrhoea primarily relies on consistent condom use. Early diagnosis and treatment are also crucial, and cephalosporin antibiotics, especially ceftriaxone, are the preferred treatment. However, growing antibiotic resistance requires careful monitoring worldwide.

Lyme disease

Deaths per year: Unknown

Lyme disease is a bacterial infection caused by Borrelia burgdorferi, transmitted to humans through bites from infected black-legged ticks, also known as deer ticks. Early symptoms typically include fever, fatigue, headache, and a distinctive bull’s eye-shaped rash.

If left untreated, the infection can lead to more severe issues such as arthritis, neurological problems, and heart complications (Lyme carditis).

Lyme disease has seen a notable resurgence across parts of North America and Europe. In the United States, Lyme disease is most prevalent in the Northeastern and Upper Midwest regions, including states like Connecticut, New York, and Wisconsin. According to the Centers for Disease Control and Prevention (CDC), around 476,000 Americans are diagnosed and treated for Lyme disease every year.

In Canada, reported cases have also increased, particularly in Ontario, Quebec, and Nova Scotia, with a more than tenfold increase in cases over the last decade. In Europe, countries like Germany, Austria, and Switzerland are experiencing similar trends, attributed to expanding tick habitats driven by climate change, urban sprawl, and shifts in land use.

Preventative measures are critical to controlling Lyme disease. This includes using insect repellents, wearing protective clothing, performing regular tick checks, and managing environments to reduce tick populations. Early detection and prompt treatment with antibiotics can prevent severe health complications.

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E. coli

Deaths per year: 950,000

Escherichia coli (E. coli) is a bacterium that can cause illness when certain pathogenic strains contaminate food or water. While most strains are harmless, some, such as Shiga toxin-producing E. coli (STEC), can cause severe illness.

Symptoms range from mild abdominal cramps and diarrhoea, to vomiting and fever. The illness typically lasts about 10 days, but in about 10% of cases, particularly in young children and the elderly, it can lead to haemolytic uremic syndrome (HUS) – a life-threatening condition characterised by acute kidney failure, anaemia, and low platelet counts. HUS is the leading cause of acute renal failure in children, with a case-fatality rate ranging from 3% to 5%.

E. coli outbreaks are primarily linked to undercooked meat, contaminated produce, and unpasteurised dairy products.

Cattle are the main carriers, but other animals like sheep, goats, and deer can also carry the bacteria. In recent years, there have been a number of E. coli resurgences in North America, Europe, and Asia with an increasing number of cases tied to fresh produce, suggesting that contamination during farming, harvesting, and handling is a growing concern.

Prevention of E. coli involves proper cooking, food hygiene, and strict monitoring of water and food sources.

Hantavirus

Deaths per year: Unknown

Hantavirus is a group of viruses transmitted primarily by rodents. In humans, it can lead to two syndromes: Hantavirus Cardiopulmonary Syndrome (HCPS) in North and America which has a case fatality rate of 40-50%, and Haemorrhagic Fever with Renal Syndrome (HFRS) in Europe and Asia which has a fatality rate of up to 12%.

More than 200,000 cases of hantavirus occur globally each year. China reports the most HFRS related deaths in the world, with almost 210,000 cases of HFRS and 1,855 deaths reported between 2004 and 2019. 

Meanwhile, in 2020 Finland and Germany claimed 85% of HFRS cases in the EU/EEA, with Finland alone accounting for 71%. The overall rate of infection in Europe fluctuated between 0.4 and 1.0 cases per 100,000 from 2016 to 2020, with no significant long-term trend.

Hantavirus infections are more common in males, particularly those over 25, and tend to increase during summer vacations or winter rural activities.

The resurgence of hantavirus infections is linked to environmental changes that increase human-rodent contact, such as deforestation and urban expansion. There is currently no licensed vaccine for hantavirus, so prevention relies on rodent control and minimising exposure to rodent droppings. Public health strategies emphasise education and preventive actions to reduce infection risk.

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Dengue fever

Deaths per year: 6,892

Dengue is a viral infection spread by Aedes mosquitoes. About half of the global population is at risk, with 100–400 million infections estimated each year, primarily in tropical and subtropical regions.

The disease ranges from mild fever, headache, body aches, and rash to severe forms causing internal bleeding and organ failure. Severe dengue can be fatal without hospital care, and those infected for a second time are at greater risk of more grievous symptoms.

Dengue cases have surged globally, with a historic peak of over 6.5 million cases in 2023, and nearly 7,000 reported deaths. Dengue fever is endemic in over 100 nations, particularly in Asia, which bears about 70% of the global burden.

Factors driving the increase include climate change, urbanisation, and changing mosquito habitats, with regions like the Americas and Southeast Asia seeing significant outbreaks.

Preventing dengue relies on controlling mosquito populations and protecting against bites. Strategies include wearing protective clothing, using insect repellents, and managing water storage to reduce mosquito breeding. No specific treatment exists, and care focuses on pain relief and hydration. A vaccine, QDenga, is available for children in some high-risk areas, with other vaccines in development.

The resurgence of hantavirus infections is linked to environmental changes that increase human-rodent contact, such as deforestation and urban expansion. There is currently no licensed vaccine for hantavirus, so prevention relies on rodent control and minimising exposure to rodent droppings. Public health strategies emphasise education and preventive actions to reduce infection risk.

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West Nile virus

Deaths per year: approx. 128 confirmed

West Nile virus, first identified in Uganda in 1937, is a mosquito-borne disease primarily transmitted to humans through bites from infected mosquitoes.

While approximately 80% of infected individuals remain asymptomatic, the virus can lead to severe neurological complications, including encephalitis and meningitis, particularly in individuals over 50 and those with compromised immune systems.

West Nile virus is most prevalent in North America, particularly in the United States and Canada, as well as parts of Europe, Africa, and the Middle East. 

The risk factors contributing to the spread of West Nile virus are closely tied to environmental changes, such as rising temperatures, urbanisation, and the presence of stagnant water, which create ideal breeding conditions for mosquitoes.

There is as-yet no vaccine for West Nile virus, so prevention strategies are largely focused on community education and mosquito control measures, including the use of repellents, nets, and public health initiatives aimed at reducing mosquito populations.

Ongoing surveillance of animal populations, especially birds and horses, is essential for early detection of West Nile virus activity, as outbreaks in these groups often precede human cases.

Tuberculosis

Deaths per year: 1.3 million

Tuberculosis (TB) is a serious bacterial infection caused by Mycobacterium tuberculosis, primarily affecting the lungs but capable of spreading to other parts of the body, such as the brain and spine.

In 2022, TB claimed approximately 1.3 million lives, making it the second leading infectious killer worldwide, just after COVID-19.

TB poses a significant public health challenge, particularly in regions such as South and Southeast Asia, Africa and Eastern Europe. The resurgence of TB in these areas can be attributed to various factors, including the emergence of drug-resistant strains, co-infection with HIV, and overcrowding.

Symptoms of TB include a persistent cough, chest pain, fever, night sweats, and weight loss. While about 80% of individuals infected with TB bacteria remain asymptomatic, a small proportion will develop active TB disease, which is contagious and requires immediate medical intervention.

Diagnosis typically involves rapid molecular tests, while treatment consists of a strict regimen of antibiotics for four to six months. However, the rise of multidrug-resistant TB (MDR-TB) has become a critical public health crisis, necessitating more complex and costly treatment options.

Preventative measures against TB include early diagnosis and treatment with antibiotics, as well as vaccination with the Bacillus Calmette-Guérin (BCG) vaccine, which is effective in preventing severe forms of TB in children.

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Cholera

Deaths per year: 21,000-143,000

Cholera is an acute diarrheal disease caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. Although most people infected experience mild or no symptoms, the disease can cause severe diarrhoea that can lead to dehydration and death within hours if untreated.

Each year, an estimated 1.3 to 4.0 million cases of cholera occur globally, resulting in as many as 143,000 deaths.

The disease is primarily associated with poverty and inadequate access to clean water and sanitation, which facilitates its rapid spread.

Cholera remains a significant global health threat, often serving as an indicator of inequity and poor social development.

Cholera outbreaks are particularly common in areas with compromised water and sanitation systems, such as peri-urban slums and camps for displaced persons or refugees. Risk factors include humanitarian crises, unplanned urbanisation, and climate change, which disrupt water supply systems and increase exposure to contaminated environments. 

Cholera can be effectively treated with oral rehydration solutions (ORS) for mild cases, while severe cases require rapid administration of intravenous fluids and antibiotics. Preventing and controlling cholera involves improving water, sanitation, and hygiene (WASH), surveillance, treatment, and vaccination. Oral cholera vaccines (OCVs) are used in areas with high risk or ongoing outbreaks.

Pertussis (whooping cough)

Deaths per year: 160,700

Pertussis, commonly known as whooping cough, is a highly contagious respiratory disease caused by the bacterium Bordetella pertussis. It spreads easily through coughing and sneezing, producing toxins that cause severe coughing fits, often followed by a “whooping” sound during inhalation.

Coughing spells can make it difficult to breathe, eat, or sleep, and may lead to complications like cracked ribs, pneumonia, or even hospitalisation.

Before vaccines became widespread in the 1940s, whooping cough caused around 200,000 infections and 9,000 deaths annually in the U.S. Despite significant progress, whooping cough has resurged in North America, Europe, and Australia, mainly due to declining vaccination rates and waning immunity.

Booster shots are needed throughout life since the protection from childhood vaccination wears off, leaving adolescents and adults susceptible. Infants under three months are most at risk, often catching the infection from unknowing older siblings, parents, or caregivers.

Preventing whooping cough relies on vaccines like the DTaP for children and Tdap boosters for teens and adults. Worldwide, there are about 24.1 million cases annually, resulting in 160,700 deaths, primarily in children under five.

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Influenza (Flu)

Deaths per year: 700,000

Influenza, commonly known as the flu, is a contagious viral infection that affects the respiratory system. Symptoms include fever, chills, body aches, sore throat, and cough. The flu virus mutates frequently, leading to seasonal outbreaks each year.

Seasonal influenza causes around 700,000 deaths globally each year, primarily from respiratory and cardiovascular complications.

Seasonal influenza causes around 700,000 deaths globally each year, primarily from respiratory and cardiovascular complications.

Although the risk of dying from the flu has declined significantly over the past century due to better sanitation, healthcare, and vaccination, the disease remains a major burden, particularly in regions with limited healthcare access and among ageing populations.

Historically, flu mortality has decreased because of improved hygiene practices and the development of vaccines, which are updated annually to match circulating strains. However, severe flu seasons can still occur when new strains emerge through “antigenic drift” or “antigenic shift,” making the virus more infectious and sometimes deadlier. Past influenza pandemics, such as the Spanish flu, resulted from such shifts, causing millions of deaths worldwide.

To reduce the impact of seasonal influenza, increased vaccination coverage and better healthcare access are essential, especially in lower-income countries. Continued improvements in global health infrastructure can further decrease the flu’s burden, building on the significant progress already made over the past decades.

Pneumonia

Deaths per year: 2.5 million

Pneumonia is a severe lung infection caused by bacteria, viruses, or fungi, leading to inflammation of the alveoli, which fill with pus and fluid. This condition makes breathing painful and reduces oxygen intake.

Pneumonia remains one of the leading causes of death worldwide, particularly affecting children under five and adults over 70.

The infection spreads primarily through respiratory droplets when an infected person coughs or sneezes.

The global burden of pneumonia has shifted over recent decades. Child mortality from pneumonia has significantly decreased, with annual deaths dropping by almost two-thirds since 1990 due to better access to vaccines, antibiotics, and improvements in sanitation and nutrition.

However, the number of deaths among older adults has increased, primarily because of ageing populations. In 2019, over one million deaths were reported among those aged 70 and older, with the highest mortality rates seen in sub-Saharan Africa and South Asia.

Prevention and treatment strategies include vaccination, reducing air pollution, and early medical intervention with antibiotics and oxygen therapy. Despite advances, pneumonia remains most prevalent in low-income regions, earning its label as “the ultimate disease of poverty” due to limited healthcare access and resources.

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