Abstract
Surveillance for acute flaccid paralysis (AFP) cases are essential for polio eradication. However, as most poliovirus infections are asymptomatic and some regions of the world are inaccessible, additional surveillance tools require development. Within England and Wales, we demonstrate how inclusion of environmental sampling (ENV) improves the sensitivity of detecting both wild and vaccine-derived polioviruses (VDPVs) when compared to current surveillance. Statistical modelling was used to estimate the spatial risk of wild and VDPV importation and circulation in England and Wales. We estimate the sensitivity of each surveillance mode to detect poliovirus and the probability of being free from poliovirus, defined as being below a pre-specified prevalence of infection. Poliovirus risk was higher within local authorities in Manchester, Birmingham, Bradford and London. The sensitivity of detecting wild poliovirus within a given month using AFP and enterovirus surveillance was estimated to be 0.096 (95% CI 0.055-0.134). Inclusion of ENV in the three highest risk local authorities and a site in London increased surveillance sensitivity to 0.192 (95% CI 0.191-0.193). The sensitivity of ENV strategies can be compared using the framework by varying sites and the frequency of sampling. The probability of being free from poliovirus slowly increased from the date of the last case in 1993. ENV within areas thought to have the highest risk improves detection of poliovirus, and has the potential to improve confidence in the polio-free status of England and Wales and detect VDPVs.
Highlights
Indigenous wild poliovirus has been not been reported within England and Wales since the 1970s [1]
acute flaccid paralysis (AFP) surveillance was instituted throughout the United Kingdom by 1991 where children
When combining these data together to estimate the probability of poliovirus circulation, 21 local authority (LA) comprise of over 50% of the estimated risk and several of these LAs are located within cities including Manchester, Birmingham and Greater London (Fig. 2 and Table 3)
Summary
Indigenous wild poliovirus has been not been reported within England and Wales since the 1970s [1]. The elimination of poliomyelitis was achieved largely through vaccination of children and adults, using both the oral and inactivated polio vaccines (OPV and IPV, respectively). In 2004, the OPV was replaced by the IPV owing to the lower risk of vaccine-associated paralytic poliomyelitis (VAPP) cases. After the introduction of vaccination wild poliomyelitis cases quickly reduced in number; sporadic imported cases of wild poliomyelitis cases were reported within England and Wales until the 1980s, which emphases the need for high immunisation rates until polio is eradicated globally [2]. Across the decades from endemicity to elimination within England and Wales, surveillance for poliomyelitis has required adaptation. All cases of acute flaccid paralysis (AFP, the typical clinical presentation of poliomyelitis) in children
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