Accidental work-related (laboratory) release of a hazardous pathogen

Impact 5
upper risk error bar
upper likelihood error bar risk indicator
lower likelihood error bar
lower impact error bar
Impact & Likelihood
Impact key
5 Catastrophic
4 Significant
3 Moderate
2 Limited
1 Minor
Likelihood key
5 >25%
4 5-25%
3 1-5%
2 0.2-1%
1 <0.2%


This risk involves the accidental release of a hazardous pathogen from a laboratory in the UK. Operators of these sites must meet strict containment and safety requirements to work with these types of pathogens and develop emergency procedures to mitigate this risk. The UK has a well-established regulatory system to ensure that operators fulfil these responsibilities effectively.


The reasonable worst-case scenario is based on the accidental release of an infectious influenza-type pathogen from a UK laboratory. It is assumed that the pathogen would cause an infection that takes several days to emerge and spreads via close contact. This could result in fatalities and casualties requiring hospital treatment, along with cases that can be resolved without the need for hospital admission. The incident could last for several weeks until all contacts are traced and treated.

Key assumptions

It is assumed that the outbreak would be identified and contained quickly, without spreading geographically. This would result in a predominantly local outbreak, rather than progressing into an epidemic. The pathogen would be quickly identifiable due to strict regulatory requirements on working with pathogens of this nature. Antiviral drugs would be effective against the virus and made available immediately to restrict further transmission. Human welfare impacts are, however, difficult to estimate with confidence.


The speed of spread within the community will depend very much upon the transmissibility of the virus, the speed with which the outbreak is identified and appropriate mitigation measures enacted, including the efficacy and availability of antivirals. There are also unquantifiable variabilities in terms of individual human immune response. A more likely scenario is that a laboratory worker who is accidentally exposed to a virus during work activity would report this, enabling immediate introduction of containment measures. The worker would be referred for medical treatment and make a full recovery without the onward spread of the virus.

Response capability requirements

There could be increased demand and disruption to local hospitals. Contact tracing would be required so that all persons in contact with the virus could be identified and treated. The laboratory facilities may require full decontamination and homes of confirmed cases may also need to be deep cleaned.


Recovery will take as long as the process to identify, isolate and provide treatment for infected individuals. Longer-term complications include the risk of developing pneumonia (viral or bacterial) some time after the initial illness with some vulnerable groups being at increased risk.