Acute Flaccid Paralysis surveillance as a crucial defence against polio in India | Explained Premium

India's robust Acute Flaccid Paralysis surveillance system is crucial for maintaining its polio-free status and preventing outbreaks.

India’s polio-free status, declared in 2014, is a significant global health achievement. However, polio remains a threat, as seen in 2024 when a case of vaccine-derived poliovirus surfaced in Meghalaya, following several years without any local cases. Around the same time, the Gaza Strip reported its first paralytic polio case in 25 years, further demonstrating the lingering risks in conflict-hit regions with fragile healthcare systems or gaps in immunisation coverage. The second round of an emergency polio vaccination campaign was started on October 14 in Gaza to vaccinate an estimated 5 lakh children under ten years with a second dose of the novel oral polio vaccine type 2 (nOPV2) vaccine. These outbreaks have renewed attention to the importance of Acute Flaccid Paralysis (AFP) surveillance in India that serves as an early warning system for poliovirus circulation and is crucial to maintain India’s polio-free status.

Acute Flaccid Paralysis refers to the sudden onset of weakness or paralysis in one or both limbs without any prior injury or trauma. AFP is a clinical syndrome that is an early indicator for diseases like poliomyelitis (polio). Poliovirus is the most concerning cause of AFP, as the virus can cause irreversible paralysis and, in some cases, death. 

In India, any child under 15 who shows symptoms of AFP is immediately investigated to determine whether the paralysis is due to poliovirus or other causes. The differential diagnosis of acute flaccid paralysis includes Guillain-Barré syndrome and transverse myelitis. Less common aetiologies are traumatic neuritis, encephalitis, meningitis and spinal cord compressing tumours.

Investigating AFP cases is essential to differentiate between polio and other causes of paralysis. This allows for early detection of potential poliovirus circulation and quick response to prevent outbreaks.

Acute Flaccid Paralysis (AFP) typically manifests through weakness in one or more limbs, often accompanied by a loss of muscle tone (flaccidity), where the affected limbs become limp. In more severe cases, individuals experience difficulty in movement, which may progress to complete paralysis. Interestingly, most cases of AFP present without pain in the paralyzed limbs, differentiating it from other forms of paralysis caused by trauma or injury. 

Also read: ​Intriguing silence: On the case of polio in India, delayed official response

AFP surveillance is a cornerstone of polio eradication efforts as it enables the early detection of poliovirus, even in areas where no symptomatic cases have been identified. The World Health Organization (WHO) mandates that countries committed to polio eradication implement stringent AFP surveillance systems to ensure the virus can be detected and managed before it spreads further. With its vast and densely populated regions, this surveillance is important for India to safeguard its progress in eradicating polio.