LITERATURE UPDATE


poliovirus surveillance systems in place in the WHO European Region: AFP, clinical enterovirus, and environmental surveillance systems. A total of 4324 reported samples


were found positive for poliovirus: 477 from AFP surveillance, 394 from clinical surveillance, and 3453 from environmental surveillance. Of these, 366 were VDPV, 3952 vaccine strains, and six were wild-type poliovirus. 709 were identified as type 1, 399 as type 2, and 1944 type 3, while 1272 samples contained more than one type. Temporal and spatial association of positive environmental samples with positive samples from AFP or clinical enterovirus surveillance was found in only eight countries.


Analysis of poliovirus-positive samples


from AFP, clinical enterovirus, and environmental surveillance revealed that type 3 poliovirus was the most prevalent type detected. Most poliovirus-positive samples were identified as vaccine strains. No information on sequences was available.


Inferring Numbers of Wild Poliovirus Excretors Using Quantitative Environmental Surveillance Perepliotchikov Y, Ziv-Baran T, Hindiyeh M et al. Vaccines (Basel). 2021 Aug 6;9(8):870.


doi: 10.3390/vaccines9080870.


Response to and monitoring of viral outbreaks can be efficiently focused when rapid, quantitative, kinetic information provides the location and the number of infected individuals. Environmental surveillance traditionally provides information on location of populations with contagious, infected individuals since infectious poliovirus is excreted whether infections are asymptomatic or symptomatic. In this study, the authors describe development of rapid (1 week turnaround time [TAT]), quantitative RT-PCR of poliovirus RNA extracted directly from concentrated environmental surveillance samples to infer the number of infected individuals excreting poliovirus. The quantitation method was validated using data from vaccination with bivalent oral polio vaccine (bOPV). The method was then applied to infer the weekly number of excreters in a large, sustained, asymptomatic outbreak of wild type 1 poliovirus in Israel (2013) in a population where >90% of the individuals received three doses of inactivated polio vaccine (IPV). Evidence-based intervention strategies were based on the short TAT for direct quantitative detection. Furthermore,


a TAT shorter than the duration of poliovirus excretion allowed resampling of infected individuals. Finally, the method documented absence of infections after successful intervention of the asymptomatic outbreak. The methodologies described here can be applied to outbreaks of other excreted viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), where there are: i) significant numbers of asymptomatic infections; ii) long incubation times during which infectious virus is excreted; and iii) limited resources, facilities, and manpower that restrict the number of individuals who can be tested and re- tested.


Mucosal immunity to poliovirus Connor RI, Brickley EB, Wieland-Alter WF et al. Mucosal Immunol. 2022 Jan;15(1): 1–9. doi: 10.1038/s41385-021-00428-0.


A cornerstone of the global initiative to eradicate polio is the widespread use of live and inactivated poliovirus vaccines in extensive public health campaigns designed to prevent the development of paralytic disease and interrupt transmission of the virus. Central to these efforts is the goal of inducing mucosal immunity able to limit virus replication in the intestine.


Recent clinical trials have evaluated new combined regimens of poliovirus vaccines, and demonstrated clear differences in their ability to restrict virus shedding in stool after oral challenge with live virus. Analyses of mucosal immunity accompanying these trials support a critical role for enteric neutralising IgA in limiting the magnitude and duration of virus shedding. This review summarises key findings in vaccine-induced intestinal immunity to poliovirus in infants, older children, and adults. The impact of immunisation on development and maintenance of protective immunity to poliovirus and the implications for global eradication are discussed.


The importance of enterovirus surveillance in a post-polio world Fischer TK, Simmonds P, Harvala H. Lancet Infect Dis. 2022 Jan;22(1): e35–e40. doi: 10.1016/S1473- 3099(20)30852-5.


Poliovirus is known to most people in the world as the cause of polio, a devastating paralytic disease from the past. Success in polio eradication has understandably translated into stricter containment plans for poliovirus, coordinated by WHO. In this Personal View, the authors


WWW.PATHOLOGYINPRACTICE.COM AUGUST 2025


discuss the impact of recent biosafety level 3+ guidelines for handling potential poliovirus-containing diagnostic specimens, which has resulted in closure of many national WHO poliovirus reference laboratories. This reduction in laboratory capacity has a knock-on effect of capability to detect and characterise non-polio enteroviruses in samples obtained from patients with neurological symptoms. The development is of concern given the widespread circulation of non-polio enteroviruses, their role as the most common cause of meningitis worldwide, and their involvement in other severe neurological conditions, such as acute flaccid myelitis and encephalitis.


These disease presentations have


increased substantially in the past decade, and have been associated with major outbreaks of enterovirus D68 and enterovirus A71, leaving many who survived with lasting paralysis and disabilities. To address this growing gap in diagnostic and surveillance capability, the authors have established the European Non-Poliovirus Enterovirus Network (also known as ENPEN) as a supra-national, non-commercial, core reference consortium. The consortium will develop, test, and implement generic surveillance platforms for non- polio enteroviruses and other emerging viral diseases.


Use of inactivated poliovirus vaccine for poliovirus outbreak response Bandyopadhyay AS, Lopez Cavestany R, Blake IM et al. Lancet Infect Dis. 2024 May;24(5):e328–e342. doi: 10.1016/ S1473-3099(23)00505-4. Erratum in: Lancet Infect Dis. 2024 Feb;24(2):e83. doi: 10.1016/S1473-3099(23)00760-0.


With continued wild poliovirus transmission in Afghanistan and Pakistan and circulating vaccine-derived poliovirus in certain countries, there exists an ongoing risk of importation of polioviruses into other countries, including those that have been polio-free for decades. Diversifying the poliovirus outbreak response toolkit is essential to account for different public health and epidemiological contexts. In this Personal View, the authors discuss data on intestinal and pharyngeal mucosal immunity induced by inactivated poliovirus vaccine (IPV), previous programmatic experience of poliovirus outbreak response with IPV, and outbreak response guidelines in countries that exclusively use IPV. With recent reports of poliovirus detection in polio-free countries such as the USA and the UK, it is important to assess the


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