At around 8:00 a.m., a sealed tank containing 200 ml of infectious agents was drained to the sewer system of a pharmaceutical manufacturing plant. Contrary to standard procedure, the tank had not been decontaminated by autoclaving beforehand. The infectious agents consisted of 140 ml of poliovirus, 8 ml of hepatitis A virus, 30 ml of rabies virus, and 20 ml of inactivated poliovirus samples (type 3 infectious agents).

They were collected and held in one of the plant’s 1100 m³ pretreatment basins. This basin was left alone until its contents, which were not discharged off site, could be treated.

Two causes were identified:

• a flow issue: two types of waste (solid and liquid waste) were on the same trolley;
• an identification issued: the ‘autoclave’ identification tape was absent from the tank containing the infectious agents.

The following actions were taken to avoid a similar incident occurring:

• ‘autoclave’ identification tape is place on all liquid waste to ensure consistent practice in all the plant’s laboratories;
• the secure waste flow was redefined: the floor locations of the trolleys were marked and liquid and solid waste are systematically separated;
• a study was carried out to find alternative solutions for the sorting, decontamination, and disposal of waste;
• the organisation of the laboratory’s autoclave cycles was revised to increase capacity and reduce the amount of waste requiring treatment;
• the washing technicians received training on the instructions to be followed: tanks without ‘autoclave’ identification tape may not be opened or redecontaminated. The technicians in the bacteriological laboratory received training on the new waste flow.