Acute flaccid paralysis syndrome
Source: gov.uk (2025-04-03)

Information on the reporting, investigation and management of acute flaccid paralysis (AFP) and acute flaccid myelitis (AFM).

Acute flaccid paralysis (AFP) is a rare but serious neurological illness which is normally due to inflammation of the spinal cord, known as acute flaccid myelitis (AFM).

Acute flaccid paralysis or myelitis is characterised by rapid onset of weakness of an individual’s extremities, often including weakness of the muscles of respiration and swallowing, progressing to maximum severity within 10 days. The term ‘flaccid’ indicates weakness accompanied by hyporeflexia or areflexia in the affected limb or limbs.

In the past, AFP was commonly due to poliovirus infection.

The success of the vaccination programme means that polio is now very rare internationally and has been eliminated in the UK; however, AFP may be linked to other viral infections including non-polio enteroviruses.

Under Schedule 1 of the Health Protection (Notification) Regulations 2010, suspected cases of acute poliomyelitis (https://www.gov.uk/government/publications/polio-national-guidelines) are notifiable. In addition, from 6 April 2025, acute flaccid paralysis or acute flaccid myelitis (AFP or AFM) not explained by a non-infectious cause is also notifiable. Appropriate testing of AFP or AFM cases not explained by a non-infectious cause, to exclude polio as a causative agent, is an integral component of polio surveillance.

To report a case, please contact the local health protection team (HPT) (https://www.gov.uk/guidance/contacts-phe-health-protection-teams).

Incidents

2022 polio incident

The UK Health Security Agency (UKHSA) in collaboration with the World Health Organization (WHO) Global Specialised Polio Laboratory of the Medicines and Healthcare Regulatory Agency (MHRA) conducts routine environmental surveillance for poliovirus. In 2022, UKHSA announced that this surveillance had detected Vaccine-like Poliovirus Type 2 (February to April 2022) and then Vaccine Derived Polio Virus Type 2 (VDPV2) (May to November 2022) in sewage samples collected from the London Beckton Sewage Treatment Works. A UKHSA national enhanced incident response was established, and environmental surveillance was expanded to cover a range of sites around England. The VDPV2 was only detected in sewage samples and no associated cases of paralysis were ever reported in the UK. The last detection of VDPV2 linked to this incident was in sewage collected in London in November 2022. The WHO removed the United Kingdom from the list of polio ‘infected’ countries in December 2023 after there had been no linked VDPV2 detections for a period of 12 months.

An increase in reports of acute flaccid paralysis (AFP) in the United Kingdom in 2018 and 2019

During 2018, the United Kingdom has experienced an increase in reports of cases of AFP. As at 24 September 2019, 57 cases had been identified since 1 January 2018 with a peak in October 2018. The increase was temporally associated with an upsurge in enterovirus (EV) D68 activity. A national task force has been established and investigations are ongoing (Eurosurveillance volume 24, issue 6, published 7 February 2019 (https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2019.24.6.1900093)).

Data

Current enterovirus strains detected (https://www.gov.uk/government/publications/enterovirus-strain-characterisation) in the Virus Reference Department in Colindale.