Major pathogenic threats in France and worldwide

In response to this situation, the Institut Pasteur performs infectious disease surveillance and lends its expertise to health authorities in detecting, characterizing and monitoring emerging and circulating pathogens worldwide 

Pathogenic threats: understanding and monitoring infectious risks

Major infectious disease threats today

1. Respiratory viruses: constant pressure on health systems

Acute respiratory infections continue to be among the most deadly infectious diseases worldwide. They are responsible for around 4 million deaths each year and particularly affect children and elderly people.

With more than 7 million deaths officially confirmed by WHO, the COVID-19 pandemic was a clear example of how these viruses can destabilize entire societies.

The Institut Pasteur monitors the viruses that cause respiratory infections, including influenza and SARS-CoV-2, through its dedicated National Reference Center.

2. Arboviruses: unprecedented expansion, including in mainland France

Viruses are not only transmitted through airborne particles. The progression of mosquito-borne viruses is one of the most worrying trends in public health today.

Arboviruses – diseases such as dengue, chikungunya, Zika and yellow fever which are spread by mosquitoes and other arthropods – are on the rise worldwide. Their expansion is directly linked to climate change and the globalization of trade.

The threat is becoming all too real in France, where the tiger mosquito (Aedes albopictus), originally from South-East Asia and first reported in mainland France in 2004, has colonized nearly four-fifths of the country in just 20 years.

In 2025, more than 830 people who had not traveled to tropical regions were infected with chikungunya or dengue in mainland France. At least 1,073 imported cases of chikungunya were reported, giving rise to 788 locally acquired cases.

The health authorities managed to curb transmission through an effective surveillance strategy and swift mosquito control measures. But every new reported case increases the risk that these viruses will take hold in mainland France.

The tiger mosquito can also transmit the Zika virus, responsible for severe neurological complications and serious congenital malformations in newborn babies. It is also compatible with the Usutu and West Nile viruses, which mainly affect birds but can also infect humans.

The Institut Pasteur monitors arboviruses (dengue, Zika and chikungunya), hantaviruses and the Plasmodium parasites that cause malaria via its dedicated CNRs.

3. Increasingly frequent disease outbreaks

As well as arboviral diseases, other infectious diseases continue to cause brutal outbreaks, often in fragile contexts.

Outbreaks of diseases such as cholera, Ebola, plague and polio are on the rise, driven by globalization, rapid urbanization and deteriorating health conditions in some world regions.

• Cholera caused over 6,000 deaths in 2024, around 50% more than in 2023, and the number of countries affected rose from 45 to 60.
• Hemorrhagic fevers like Ebola continue to be a recurrent threat in West and Central Africa, with a constant risk that they will be exported to other continents.
• The Institut Pasteur monitors the pathogens responsible for these outbreaks, including Vibrio (cholera), hemorrhagic fever viruses (Ebola and Lassa), Yersinia (plague), enteroviruses (polio) and the rabies virus.

4. Tuberculosis: the world's most deadly bacterial infection

• Tuberculosis remains a deadly global scourge. In 2023, more than 10 million people fell ill with tuberculosis and around 1.25 million died from the disease, mainly in low- and middle-income countries (WHO). The emergence of strains with multiple antibiotic resistance is complicating efforts to tackle the disease. The Institut Pasteur is closely involved in tuberculosis research, both basic science and the development of novel diagnostic and therapeutic tools.

5. Antimicrobial resistance: the silent threat

Antimicrobial resistance (AMR), meaning the ability of pathogens to resist treatment, is seen by WHO as one of the top ten global public health threats.

Antibiotic resistance alone is already responsible for 1.3 million deaths each year, a number that could rise to 39 million by 2050. The potential economic impact is also huge, with cumulative losses estimated at $100,000 billion by 2050 owing to rising mortality, longer hospital stays and productivity losses.

AMR involves many of the pathogens monitored by the Institut Pasteur, including bacteria responsible for meningitis (meningococcal bacteria and Haemophilus influenzae), foodborne pathogens (Salmonella, Listeria, Shigella and E. coli) and invasive mycoses (Candida, Aspergillus and Cryptococcus), which are becoming increasingly resistant to antifungals.

6. Climate breakdown, a driver of infectious risks

Climate breakdown is redrawing the map of infectious diseases. According to a 2022 study published in Nature Climate Change, 58% of infectious or allergic diseases have already been exacerbated by greenhouse gas-related climate change.

Rising global temperatures accelerate mosquito life cycles and shorten the incubation time of the viruses they carry, so that they can be transmitted to humans more quickly. Modeling by Imperial College London and WHO suggests that deaths related to yellow fever in Africa could increase by between 11 and 25% by 2050.

According to WHO, between 2030 and 2050, climate change is expected to cause 250,000 additional deaths each year from malaria, malnutrition, diarrheal diseases and heatwaves.

Monitoring pathogenic threats in France

In France, pathogen surveillance is conducted by a network of National Reference Centers (CNRs) coordinated by Santé publique France. 

These specialist laboratories serve as sentinels for the health system, identifying, characterizing and monitoring the development of pathogenic microorganisms in the country.

The Institut Pasteur is responsible for monitoring 17 categories of pathogens:

Viruses

•    Respiratory viruses, including influenza and SARS-CoV-2
•    Rabies virus
•    Viruses responsible for hemorrhagic fevers, such as Lassa and Ebola
•    Hantaviruses, spread by rodents
•    Arboviruses, including dengue, Zika, and chikungunya
•    Enteroviruses and parechoviruses, particularly those that cause polio

Bacteria

•    Clostridium, including the bacteria responsible for botulism
•    Yersinia, including the plague bacillus
•     Corynebacterium, including the bacteria responsible for diphtheria
•    Shigella, Salmonella and Escherichia coli, responsible for foodborne infections
•    Leptospira, which can cause kidney failure
•    Listeria, including the "refrigerator bacteria" that cause listeriosis
•    Meningococci and Haemophilus influenzae, responsible for meningitis
•    Vibrios, including the cholera agent
•    Bordetella, including the whooping cough bacillus

Fungi

•   Candida, Aspergillus, Cryptococcus and other invasive mycoses
 

Parasites

•    Plasmodium, responsible for malaria
 

Surveillance is carried out by 14 National Reference Centers (CNRs) in Paris and Lyon, and four CNR-associated laboratories in French Guiana.
 

 This nationwide surveillance is part of the broader strategy pursued by Santé publique France, which coordinates all the CNRs hosted by institutions across the country.
 

Monitoring pathogenic threats worldwide

Much like pathogens themselves, surveillance does not stop at national borders!
Recent crises like the COVID-19 pandemic, the Ebola outbreaks in West and Central Africa, and the global expansion of dengue and mpox remind us that infectious agents circulate globally. A virus that emerges in a tropical forest can reach cities on every continent in the space of a few weeks.

The Institut Pasteur hosts eight WHO Collaborating Centers (WHOCCs), which are responsible for monitoring, coordinating surveillance efforts, alerting authorities and responding to disease outbreaks worldwide: 

•    Enteroviruses/polio
•    Leptospirosis
•    Listeria
•    Bacterial meningitis
•    Rabies
•    Salmonella
•    Monitoring antimalarial drug resistance
•    Yersinia
 

This international surveillance is part of a broader strategy pursued by the World Health Organization, which coordinates all the WHOCCs across the world.