General information, not a diagnosis Method and limitations

09Knowledge Atlas

Understand everything,
danger to protection.

An overview of biological risks: what can cause harm, how exposure occurs, what changes the risk, what barriers are useful and where to find appropriate references. The content links human, animal, plant, environmental and professional health.

  • 13 main chapters
  • 5 families of infectious agents
  • Multi-hazard approach
  • 36 defined concepts

00Map of the guide

Choose an input angle

Biological risk is not limited to epidemics. It also covers work, care, laboratories, food, water, animals, plants and ecosystems.

01Fundamentals

The danger exists; the risk is built

One biological hazard is an intrinsic property of an agent, organism or biological material that may cause infection, allergy, poisoning or other harmful effect. The Risk expresses the possibility that this damage may occur in a given situation and the extent of its consequences.

Therefore, the presence of a micro-organism does not automatically mean that a person will be infected. In order for damage to occur, a chain must link a source, a release, a journey, a door of entry and a receptive host. Interrupting a single link can already reduce the risk.

Multidisciplinary team evaluating environmental samples near a wetland
AI-generated illustration, not evidence of a health event. The assessment links the field, samples and knowledge in human, animal and environmental health.
Hazardability to harmandExposuredose, duration, routeandVulnerabilityhost and context→Riskprobability and severity

The logic is that these components are not a numerical risk calculation formula.

Four types of effects

  • Infectious: an agent multiplies or persists in a host and may cause a communicable disease or not.
  • Toxic: a toxin of biological origin acts even without multiplication of the producing organism.
  • Allergy: proteins, spores or biological fragments trigger an inadequate immune response.
  • Immunological or inflammatory: Some components may cause a reaction without active infection.

Risk may involve a person, population, livestock, culture, food chain, ecosystem or continuity of an essential activity. The right level of analysis therefore depends on the question asked.

02Types of biological agents

Very different properties

Biological agents do not all respond to the same treatments, do not survive as long in the environment and do not use the same routes of transmission.

V

Virus

They need host cells to multiply. Their envelope, stability and transmission pathways influence prevention measures.

Examples: influenza, measles, viral hepatitis, dengue.
B

Bacteria

A wide variety of single cell organisms; some produce toxins or develop antibiotic resistance.

Examples: tuberculosis, legionellosis, salmonellosis, leptospirosis.
F

Mushrooms

Yeasts and moulds can cause infections, allergies or toxic effects, especially in fragile people.

Examples: candidiasis, aspergillosis, dermatophytosis.
P

Parasites

Protozoans, helminths and ectoparasites have sometimes complex cycles, with vectors or intermediate hosts.

Examples: malaria, toxoplasmosis, schistosomiasis, scab.
Pr

Let us pray

Poorly compliant proteins responsible for rare diseases; their unusual resistance requires specific procedures.

Example: Creutzfeldt-Jakob disease.
T/A

Toxics and allergens

The danger can come from a biological product or fragment, without infection or living organism.

Examples: botulinum toxin, endotoxins, allergenic spores.
Antimicrobials are not interchangeableAntibiotics target certain bacteria, not viruses. Antivirals, antifungals and antiparasitic medicines have their own indications. Their choice is the responsibility of a professional and, as the case may be, a biological diagnosis.

03Transmission and exposure

The exposure route controls protection

Aerated study room where several people work with open windows
AI-generated illustration, not evidence of a health event. Ventilation, duration and occupancy of a site alter respiratory exposure.
01

Air and respiratory particles

Particulate matter of varying sizes can be emitted by breathing, speaking, coughing or during certain processes. Distance, duration, air renewal, volume and activity change exposure.

02

Direct or indirect contact

Skin, mucous membranes, lesions, hands, surfaces or objects can contribute to the transmission depending on the ability of the agent to survive and the frequency of contact.

03

Fecooral use, food and water

Contamination may occur during production, preparation or storage, or by inadequately protected or treated water.

04

Blood and biological fluids

Piqûres, cuts, projections on mucous membranes and some intimate contacts expose to specific agents; precautions depend on the gesture and fluid involved.

05

Vectors and animals

Mosquitoes, ticks, phlebotomas, fleas or other arthropods can transmit an agent. Morsures, scratches, excrement and professional contacts also count.

06

Soil, dust and environment

Spores, bio-aerosols, stagnant water, sludge, organic waste and plant materials can create respiratory, skin or digestive exposure.

07

Vertical transmission

Some agents may pass during pregnancy, childbirth or breastfeeding. The risk varies greatly depending on the agent and the time of exposure.

Colonization, contamination, infection and disease

These words are not synonymous. A surface may be contaminated without an infected person. An organism can colonize a host without symptoms. An infection can remain asymptomatic, while a disease is clinically relevant. This distinction avoids drawing alarming conclusions from a simple detection result.

04Exposure media

The context changes everything

The same agent does not create the same level of risk in a home, hospital, livestock, sewage treatment plant or laboratory.

Community

Daily life

Accommodation, school, transportation, community events, sexuality, sport and social contacts.

Care

Health facilities

Fragile patients, invasive gestures, medical devices, exposure to blood and infections associated with care.

Work

Occupational exposures

Care, personal assistance, agriculture, livestock, slaughterhouses, waste, sanitation, search and rescue.

Laboratory

Biological manipulation

Concentration, amplification, process aerosols, cultures and sharp or sharp objects.

Food

From the field to the plate

Primary production, processing, cold chain, cooking, cross-contamination and drinking water.

Animals

Livestock and wildlife

Zoonoses, animal movements, vectors, wildlife interfaces and veterinary health.

Environment

Water, air, soil and waste

Releases, bio-aerosols, wastewater, composting, flooding and land-use changes.

Mobility

Travel and gatherings

Destination, season, duration, activities, access to care and recommendations specific to the territory.

05Evaluate

A method in seven questions

  1. 1
    What's the danger?

    Known or suspected agent, possible effects, stability, relevant dose and prevention or treatment options.

  2. 2
    What's the source?

    Person, animal, culture, sample, food, water, waste, surface, equipment or environment.

  3. 3
    Who can be exposed?

    Number of people, workers, public, sensitive species and more vulnerable groups.

  4. 4
    By what way?

    Inhalation, ingestion, mucous contact, injured skin, inoculation, vector or combination of pathways.

  5. 5
    What dose and for how long?

    Concentration, frequency, proximity, duration, volume processed and dispersal potential.

  6. 6
    What barriers exist?

    Removal, containment, ventilation, procedure, training, vaccination, hygiene and equipment.

  7. 7
    What remains after these measures?

    The residual risk must be acceptable, monitored and reassessed when an activity or information changes.

A "probability × gravity" matrix may help prioritize, but it does not replace the data or the competent judgement. Categories must be defined in advance, documented and adapted to the sector.

06Prevent

Putting the most robust barriers first

Effective prevention combines several levels. Measures that affect the source or environment generally protect more people and depend less on a perfect gesture repeated all day long.

  1. 01

    Avoid or delete

    Do not perform an unnecessarily exposing task, remove a source or choose a method that does not require the agent.

  2. 02

    Substitute or reduce

    Use a less hazardous agent, volume or process when the expected result allows.

  3. 03

    Confining and ventilating

    Pregnant, source capture, zone separation, clean/salting circuits and suitable air renewal.

  4. 04

    Organize

    Simple procedures, limited access, suitable staff, cleaning, maintenance, waste, training and reporting.

  5. 05

    Protecting individually

    Gloves, clothing, eye or respiratory protection selected by risk, properly adjusted, removed and eliminated.

  6. 06

    Monitor and learn

    Controls, exercises, incident tracking, feedback and re-evaluation after any change.

Hand hygiene

Useful at key times, with appropriate technique and product. Gloves do not replace hygiene and can transfer contamination.

Inland air

Reduce occupancy, increase intake of outdoor air, filter when indicated, and limit emissions at source complement each other.

Vaccination

Where it exists and is recommended, it reduces certain risks but does not replace other barriers or context instructions.

Practical guide to preventionWHO · Prevention of infections

07Biosecurity and biosafety

Control risks without reducing security to a number

The biosecurity aims to prevent accidental exposure and unintentional release of biological agents. The biosafety is designed to prevent loss, theft, hijacking, unauthorized access or malicious use. Both are based on a culture of responsibility, verified competencies and local assessment.

Containment levels (often referred to as L1 to L4 or BSL-1 to BSL-4) describe sets of practices, equipment and installation characteristics. They must not be assigned from the name of an agent alone: procedure, quantity, concentration and regulation also count.

L1

Low-risk work with basic microbiological practices and adapted surfaces.

L2

Improved access, practices, equipment and decontamination for moderate risk agents.

L3

High confidence for activities that can generate serious infectious aerosols; specialized installation and training.

L4

Maximum confederation reserved for highly specialized work, in dedicated and highly regulated installations.

A complete approach covers the life cycle: ordering, receiving, inventory, storage, handling, transport, decontamination, waste, maintenance, incident and closure. It also integrates human factors: workload, understanding procedures, right to alert and learning without concealment.

No universal protocolDecontamination and equipment shall be validated for the agent, matrix, surface and process. An on-line general fact sheet does not replace the biosecurity officer's assessment or regulatory requirements.

08One Health

One system, several observation points

Human health, animal health, plant health and ecosystem health are linked, but not identical. The One Health approach organizes their cooperation.

H

Humans

Clinical cases, behaviours, vaccination, access to care and social factors.

A

Animals

Livestock, pets, wildlife, movements and veterinary services.

V

Plants

Pests, crop pathogens, biodiversity and food security.

E

Environment

Water, soil, climate, waste, habitats, pollution and land uses.

ONE
HEALTHWatching together
acting at source

The interfaces are particularly important: animal husbandry, wastewater-mild, food-consumers, climate-vectors and antimicrobial use in several sectors. Cross-checking data may reveal a problem earlier and avoid that one measure taken in one domain moves the risk to another.

Understanding the One Health Approach →WHO · One HealthFAO · One HealthWHO · One Health

09Antibioresistance

When treatments lose their effectiveness

Antimicrobial resistance occurs when bacteria, viruses, fungi or parasites evolve so that they no longer respond adequately to certain drugs. The antibioresistance specifically concerns bacteria and antibiotics.

Selection is favoured by unnecessary or incorrect use, but also by essential treatments. Preventing infections, improving diagnosis, choosing the right molecule, the right dose and duration, monitoring resistance and limiting environmental releases are only one strategy.

Human health

Reasoned prescription, infection prevention, diagnosis, vaccination and continuity of care.

Animal health

Prevention in livestock farming, biosecurity, veterinary monitoring and prudent use of antimicrobials.

Food

Hygiene, control of production lines and reduction of the transmission of resistant bacteria.

Environment

Wastewater, effluent, pharmaceutical manufacturing and dissemination of resistance genes.

Never interrupt, prolong, share or reuse an antimicrobial without proper advice. An improvement in symptoms does not prove that the infection is controlled, and any remaining treatment may be inappropriate or dangerous.

Read the file on antibiotic resistance →

10Emerging risks

The emergence often results from several changes

A new agent attracts attention, but a threat may also emerge because a known agent arrives in a new area, changes host, becomes resistant or encounters a more exposed population.

01

Climate and seasons

Temperature, rain, drought and extreme events change vectors, water, food and behaviour.

02

Land use

Deforestation, urbanization, irrigation and habitat fragmentation are transforming the interfaces between species.

03

Mobility

Travel, trade and movements of animals or plants accelerate certain geographical introductions.

04

Food systems

Concentration, chain complexity, breeding conditions and distribution can amplify or broadcast an event.

05

Inequality and conflict

Reduced access to water, care, housing or vaccination increases exposure and delays detection.

06

Biological evolution

Mutations, recombination, genetic exchange and selection change transmissibility, tropism or resistance.

07

Technology

Modern biology brings diagnostics, vaccines and knowledge, but requires governance, safety and evaluation of dual uses.

08

Monitoring capabilities

More detection can lead to an increase without the actual incidence increasing in the same proportion.

An alert must therefore be interpreted with its denominator, methods and history. A multiplication of reports may reflect a spread, a better case search, a new definition or several of these factors at a time.

11Governance and preparedness

Different texts for different functions

International cooperation is not based on a single document. The International Health Regulations (IHR) organises in particular the detection, notification and response to transboundary public health risks. The amendments adopted in 2024 are applicable to the vast majority of States parties since 19 September 2025; however, the legally applicable version may differ for some States that have notified a rejection.

I'm not sure what I'm doing.WHO Pandemic Agreement was adopted on 20 May 2025. In its publication of 18 September 2026, consulted on 3 October, WHO describes the continuation of negotiations on the Annex on Pathogens and Benefit-sharing (PABS) at the end of the eighth meeting of the Intergovernmental Group. The Agreement should therefore not be presented as fully operational or entered into force.

The Biological Weapons Convention is a disarmament issue and prohibits biological and toxin weapons. It does not replace laboratory biosecurity rules, labour regulations or public health procedures. These frameworks complement each other without having the same purpose.

RSI

International alert, essential capabilities, temporary or permanent contact points and recommendations.

Pandemic agreements

Prevention, preparedness, response, equity and countermeasures; PABS process still incomplete at the revision date.

National law

Reporting requirements, occupational health, laboratories, transport, waste and emergencies remain locally specified.

Check versionFor a legal, regulatory or operational decision, see the official text applicable to your country and its date of entry into force. A pedagogical synthesis is not a legal opinion.

12After an exhibition

Act quickly, without improvising

  1. Make yourself safe.

    Stop exposure if it can be done without creating an additional hazard. Get away from the source and alert the exposed people.

  2. Apply the intended immediate gesture.

    Follow the protocol of the place or product: rinse, wash, remove contaminated clothing or other appropriate action. Do not use an unspecified aggressive product.

  3. Report and document.

    Note the hour, the place, the type of material, the track, the duration, the protections and the first measurements. At work, inform the designated manager without delay.

  4. Request a competent assessment.

    Contact a professional, occupational medicine, poison control centre, infectious disease service or authority indicated according to the context. Some post-exposure measures are time sensitive.

  5. Monitor according to instructions.

    Do not rely on the immediate absence of symptoms. Follow the recommended follow-up, tests, precautions and appointments.

  6. Analyze the incident.

    Once the emergency is managed, identify the technical and organisational causes to avoid repetition.

EmergencyIn case of respiratory difficulty, loss of consciousness, uncontrolled bleeding, severe reaction or immediate danger, call emergency services. Do not delay the call to search for an online answer.

13Glossary

36 words to read health information

Search for a definition and find its documentary reference →

Short definitions to decode newsletters, risk assessments and scientific articles.

Biological agent
Micro-organism, cell culture, endoparasite or biological entity likely to have a harmful effect.
Antigen
An element recognized by the immune system and capable of triggering a specific response.
Asymptomatic
Infection or condition not producing observable symptoms at the given time.
Bio-aerosol
Particulate matter of biological origin suspended in the air, viable or not.
Biosafety
Measures to avoid accidental exposure and unintentional release.
Confirmed case
Person or event meeting the confirmation criteria defined by the surveillance.
Contact case
A person who has had a defined contact with a case or source for a specified period of time.
Cluster
Unusual clustering of cases in a given place and period.
Colonization
Durable presence of a micro-organism without tissue invasion or necessary disease.
Contamination
Presence of an undesirable agent or material on a surface, medium or product.
Decontamination
A process that reduces a contaminant hazard to an acceptable level.
Disinfection
Inactivation of microorganisms on objects or surfaces according to a given objective.
Endemic
The usual or expected presence of a disease in a population or area.
Epidemic
Occurrence of cases greater than expected in a population, place and period.
Exposure
Contact of a person, animal, plant or environment with a source of danger.
Host
An organization that can host an agent, temporarily or permanently.
Impact
Number of new events in a population during a period.
Infection
Penetration and multiplication or persistence of an infectious agent in a host.
Lethality
Proportion of deaths among defined cases of disease over a period.
Pandemic
Epidemic that extends to many countries or continents with sustained transmission.
Pathogenicity
Ability of an agent to cause disease in an infected host.
Incubation period
Interval between infection and onset of symptoms.
Prevalence
Proportion of a population with a state at one time or over a period.
Tank
Population or environment in which an agent is maintained and from which it can be transmitted.
Residual risk
Risk that remains after enforcement of control measures.
Signal
Information that may indicate a threat and that requires verification or investigation.
Biological safety
Measures against loss, theft, unauthorized access, diversion or malicious use.
Transmission
Transition from an agent from a source to a new host or middle.
Vector
Organism, often arthropod, that transports or transmits an agent between hosts.
Zoonosis
Naturally transmissible disease or infection between vertebrate and human animals.
Medical countermeasure
A product or device intended to prevent, diagnose or treat the effects of a health threat.
Intentional event
Release or deliberate use of a biological agent, to be distinguished from an accident or natural emergence.
Environmental monitoring
Search for biological signals in environments such as wastewater, in addition to clinical monitoring.
Genomic surveillance
Sequencing and analysis of genetic material of agents to monitor diversity, evolution and circulation.
Pandemic emergency
Alert level introduced in the amended IHR for certain emergencies at risk of pandemic spread and major impacts.
USPPI
International public health emergency identified by the IHR and likely to require a coordinated response.

14Frequently Asked Questions

Most common traps

Does a dangerous biological agent always cause a disease?

No. The presence of a danger is not enough. The risk depends on actual exposure, dose, route of entry, duration, ability of the agent to cause infection, and vulnerability of the person, animal or plant exposed.

Is further disinfecting ever more protective?

No. A product, concentration, contact time and surface must be compatible. Excessive or inappropriate use may expose irritants, damage materials, promote bad practices or create a false sense of safety.

Is a mask enough against all biological risks?

No. Protection depends on the route of exposure and the context. Ventilation, organisation, isolation of a source, hand hygiene, vaccination when indicated and suitable equipment complement each other. No equipment alone compensates for a poor risk assessment.

What to do after a potential exposure?

Stay away from the danger without further exposure, apply local instructions, perform immediate actions for the type of exposure, record the circumstances and contact the appropriate department or professional quickly. In case of distress or immediate danger, call the emergency room.

Further reading

These publications help you verify the concepts discussed. Disease records and directory entries each identify their sources.

The content modification date does not mean that every source has undergone a new medical review. Verification method and scope.