Gaps in surveillance leave European children at risk of acute flaccid myelitis

Gaps in surveillance leave European children at risk of acute flaccid myelitis

A new European study shows that acute flaccid myelitis, a polio-like disease that affects abnormal children, is slipping through the cracks in national surveillance, as are viral outbreaks in case disorders.

In a study recently published in the journalEurosurveillanceA large team of researchers from different institutions across Europe examined the incidence, causes and national surveillance strategies for acute flaccid myelitis (AFM) in European countries from 2016 to 2023.

background

AFM usually has a sudden onset of limb weakness, but can also affect the ability to swallow, speak, or move the eyes, making it difficult for affected children to perform everyday tasks.

Imagine your child suddenly losing the ability to move their arms or legs. This frightening reality is the hallmark of acute flaccid myelitis (AFM), a rare but serious neurological condition that primarily affects the spinal cord in children under 10 years old. Its symptoms mimic those of polio, although it is caused by other viruses. I

In recent years, spikes in AFM cases have coincided with outbreaks of enterovirus D68 (EV-D68), raising concerns about a possible association. Despite the risk of paralysis and long-term disability, AFM is widely practiced in Europe. Better monitoring is needed to understand its impact and improve preparedness. The exact triggers, natural history, and mechanisms of AFM are still under investigation. Further research is urgently needed to accurately determine the true incidence of AFM, clarify its viral triggers, and develop effective surveillance systems that can support timely diagnosis, treatment, and outbreak response.

About the study

A lead survey was distributed to members of the European Non-Polio Enterovirus Network (ENPEN), which includes clinicians and laboratory experts from 28 countries. These experts were asked to describe how AFM was monitored in their countries between 2016 and 2023. The survey included questions about surveillance strategies, changes since the 2016 case, institutions responsible for virological testing, and annual case numbers, including case numbers confirmed as EV-D68.

Participants were also asked to identify whether the data was sourced nationally or regionally. Although the survey did not request direct figures for acute flaccid paralysis (AFP), a syndrome involving sudden limb weakness, some countries have voluntarily reported these figures. Information about the type of virological testing was not systematically collected but was occasionally shared by respondents.

Responses were received from 22 institutions in 16 countries and 18 institutions were able to provide AFM case data. Case counts, including those with confirmed EV-D68 infection, were compiled for each year from 2016 to 2023. The aim was to assess incidence patterns and identify gaps in surveillance systems across Europe, as well as to investigate the temporal relationship between EV-D68 circulation and AFM peaks.

Study results

Differentiation of AFM from other neurological diseases such as transverse myelitis and Guillain-Barré syndrome often requires MRI imaging and testing of the cerebrospinal fluid for signs of inflammation.

The survey found 130 confirmed cases of AFM in 15 European countries between 2016 and 2023. Most cases, 91 or 70% in total, were clustered in 2016, 2018 and 2022, which were known to have increased EV-D68 circulation. Among the 130 total cases, 48 ​​(37%) were confirmed as EV-D68 positive.

Only Norway maintained a structured surveillance system specifically dedicated to AFM. In contrast, eight countries (Austria, Belgium, Poland, Spain, Italy, Norway, Switzerland and Torkiye) still operated legacy AFP surveillance programs originally created to track poliomyelitis. However, these systems focus primarily on excluding poliovirus and typically did not include follow-up investigations for causes such as EV-D68. In Norway, respiratory samples from AFP cases have been routinely collected since 2014, allowing more precise virus identification.

Overall, surveillance approaches have been inconsistent. In 12 of the 16 countries, testing for suspected AFM was carried out locally, while four countries relied on national referral centers. Some participants based their answers on personal experience or regional data rather than national registers, further limiting reliability.

Data from four countries, namely Spain, Poland, Norway and Switzerland, also included AFP counts totaling 751 cases. However, these numbers did not always correlate with reported AFM numbers, suggesting that AFP monitoring alone is not sufficient to accurately track AFM. This may reflect that most AFP cases are due to other conditions such as Guillain-Barré syndrome or due to possible underdiagnosis or misclassification of AFM, particularly in the absence of routine viral testing.

The three peak years for AFM cases (2016, 2018, and 2022) matched global patterns, particularly in the United States (US), where the Centers for Disease Control and Prevention (CDC) operates a dedicated AFM surveillance system. The consistency of European and US peaks supports the temporal relationship between EV-D68 and AFM states. However, the lack of a similar structured clinical surveillance system in most of Europe means that many cases are likely to go undetected or unreported.

It remains unclear whether an increase in reported AFM cases during periods of high EV-D68 circulation is due to actual peaks in incidence or to increased clinical awareness and reporting.

Conclusions

In conclusion, this study highlights significant gaps in the tracking of AFM across Europe. Only Norway has implemented a national surveillance system focused on this disabling neurological disease. The finding that 70% of reported cases occurred during known EV-D68 outbreak years reinforces a temporal connection between virus and disease peaks. However, inconsistent data collection and lack of routine testing are likely higher. To improve detection and preparedness, a European AFM repository is being developed. This shared network aims to standardize reporting, increase awareness and ultimately reduce the burden of this rare but potentially devastating disease in children.

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