Following a case of acute flaccid paralysis after infection with enterovirus type D68, we highlight current understanding of the causal role of enterovirus infection in this neurological syndrome. Acute flaccid paralysis is a rare complication of enterovirus infections. Such viruses have become a more common cause of severe respiratory-tract infections, especially in children with underlying lung disease such as asthma.

Objectives: To describe the characteristics of patients reported with acute flaccid paralysis between 1997 and 2002, and to evaluate the performance of the acute flaccid paralysis surveillance system using indicators recommended by the World Health Organization.

Design: Retrospective study.

Setting: Department of Health, Hong Kong.

Participants: Children aged younger than 15 years who were reported to the Department of Health between 1997 and 2002 with acute flaccid paralysis.

Results: Of 120 children with acute flaccid paralysis reported between 1997 and 2002, 42% were younger than 5 years of age. None of the cases were acute poliomyelitis or polio-compatible. A neurological cause was identified in 67.5% of cases, of which the most common was Guillain-Barre syndrome (42%), followed by transverse myelitis (15%). All except one of the performance indicators consistently met World Health Organization requirements and thus demonstrated the effectiveness of the acute flaccid paralysis surveillance programme. The acute flaccid paralysis notification rate consistently exceeded 1.0 per 100 000 population below 15 years of age. The requirement for adequate stool investigation was the single indicator that did not satisfy World Health Organization requirements. This highlighted the importance of maintaining physicians' awareness of acute flaccid paralysis surveillance.

Conclusion: Hong Kong should remain vigilant for acute flaccid paralysis. The effective surveillance system and its evaluation may serve as a model for surveillance of other infectious diseases.

Purpose of review: Although acute flaccid paralysis (AFP) is more frequently seen in the tropics than in temperate regions, recent outbreaks of West Nile virus (WNV) in North America have drawn attention to this important presentation. Starting with anatomical and neurophysiological considerations, this article examines data on AFP caused by WNV, and considers recent data on paralysis caused by enteroviruses, and Guillain-Barré syndrome (GBS).

Recent findings: Neurophysiological, radiological and pathological studies suggest WNV causes AFP by damaging anterior horn cells in the spinal cord. The clinical presentation is probably best described as a 'poliomyelitis-like illness', and the disease as 'WNV myelitis'. Other findings during the recent outbreaks include increasing recognition of a Parkinson's-disease like presentation, and descriptions of virus transmission in blood transfusions and transplanted organs. GBS is now recognized as several disorders characterized by immune-mediated attack on peripheral nerves: in acute inflammatory demyelinating polyneuropathy the myelin sheath and Schwann cell of sensory and motor nerves are targeted; acute motor axonal and acute motor and sensory axonal neuropathy often follow Campylobacter jejuni enteritis and are associated with antibodies against the ganglioside component of the nerve axolemmal membrane. In Asia-Pacific, enterovirus 71 has caused outbreaks of neurological diseases with AFP and encephalitis, but no single genogroup of virus appears responsible for severe disease.

Summary: Despite the near eradication of poliomyelitis, AFP caused by viruses remains an important clinical presentation. Distinguishing direct viral causes from GBS is important for public health reasons, and to avoid inappropriate therapies.

The last case of paralytic poliomyelitis caused by wild poliovirus in Brazil occurred in 1989. The interruption of the indigenous poliovirus transmission was obtained through mass immunization campaigns to eligible children and an active epidemiological and laboratorial surveillance of all cases of acute flaccid paralysis (AFP) among children under 15 y of age. This paper describes and evaluates the performance of the AFP surveillance system in different geographic areas of Brazil between 2005 and 2014, using indicators recommended by WHO. AFP surveillance indicators as well as virological investigation of polio and non-polio enteroviruses in stool samples received in the laboratory were assessed from 2005-2014. During the period, 5463 cases of AFP were investigated. Of these, 55% were males and 45% were females. Those under 5 y of age represented 48% of all cases reported and investigated. AFP notification rate was within the acceptable values with mean value of 1.3 (North), 1.4 (Northeast), 1.1 (Southern), 1.0 (Southeast) and 1.4 (Midwest) cases of AFP per 100.000 population aged 15 y as well as the adequacy of fecal specimens received in the laboratory. Sabin- related polioviruses accounted for 1.7% of the isolates while, 6.7% were non-polio enterovirus with the values ranging from 5.0% to 8.9 %. No wild-type polio was found. The AFP epidemiological and laboratorial surveillance activities have been kept at appropriate levels in Brazil. These data are a very strong indication, which supports the status of country free of polio.

Objectives: To describe the epidemiology and causes of acute flaccid paralysis (AFP) in Australian children, and the clinical features of the two most common causes of AFP, Guillain-Barré syndrome and transverse myelitis.

Methods: Monthly active surveillance for AFP was carried out through the Australian Paediatric Surveillance Unit, with AFP defined as 'acute onset of flaccid paralysis in one or more limbs or of bulbar paralysis in any child less than 15 years of age'.

Results: Between March 1995 and December 1999, 143 cases of AFP were reported (approximately 0.8 per 100000 children < 15 years of age per annum). The age range was 2 months-14 years and 59% were boys. Out of these children, 137 (96%) were hospitalized and 47 required intensive care. No case of wild or vaccine-associated poliomyelitis was identified. The most common causes of AFP were Guillain-Barré syndrome in 67 (47%) and transverse myelitis in 27 (19%). Other diagnoses included acute disseminated encephalomyelitis, trauma, tick-bite paralysis and infantile botulism.

Conclusion: The participation of paediatricians in AFP surveillance contributed to the accreditation of Australia (along with the other 36 countries of the western Pacific region) as 'polio free' by the World Health Organization in October 2000. The surveillance also provided data on the frequency of AFP and identified Guillain-Barré syndrome and transverse myelitis as the most common diagnoses. In this large national series, many other conditions that may present as non-polio AFP were identified.

During 2018, the United Kingdom experienced an increase in reports of cases of acute flaccid paralysis (AFP). As at 21 January 2019, 40 cases had been identified with a peak in October 2018. The increase was temporally associated with an upsurge in enterovirus (EV) D68 activity. Enterovirus was detected in 15 cases, mainly from respiratory tract samples; nine were typed as EV-D68. A national task force has been established and investigations are ongoing.