BACKGROUND: Despite tremendous efforts in the fight against polio, Pakistan bears the highest proportion of poliomyelitis cases among the 3 endemic countries including Afghanistan and Nigeria. Apart from insecurity and inaccessibility challenges, the substantial shift of unimmunized children from North Waziristan due to recent military operations was presumed to favor the widespread poliovirus infection in Pakistan. METHODS: To better understand the current epidemiological situation, we analyzed the virologic data of wild poliovirus type 1 (WPV1) strains detected in Pakistan during 2013-2015. RESULTS: Five genetic clusters (A-E) were identified with at least 5% nucleotide divergence in the viral protein 1 (VP1) coding region. Peshawar, Quetta, and Karachi were found to be the major endemic foci where multiple discrete genetic lineages of WPV1 were detected. Phylogenetic analysis suggests that wild poliovirus strains from endemic regions were genetically distant (with 5%-15% VP1 nucleotide divergence) from those detected in North Waziristan cases, excluding the possibility of a recent progenitor of WPV1 instigating single-source transmission across the country. Orphan lineages detected in Rawalpindi, Lahore, Hyderabad, Sukkur, and Jacobabad revealed silent transmission and the need for vigilant surveillance. Sustenance of analogous genetic lineages over a period of 3 years highlights multiple unimmunized foci present to maintain viral genetic diversity. CONCLUSIONS: Our findings are inconsistent with the hypothesis that impoverished populations from North Waziristan serve as a possible determinant of widespread poliomyelitis infection in Pakistan and further emphasize the need to scale-up clinical and environmental surveillance as well as immunization activities.
BACKGROUND: Despite tremendous efforts in the fight against polio, Pakistan bears the highest proportion of poliomyelitis cases among the 3 endemic countries including Afghanistan and Nigeria. Apart from insecurity and inaccessibility challenges, the substantial shift of unimmunized children from North Waziristan due to recent military operations was presumed to favor the widespread poliovirusinfection in Pakistan. METHODS: To better understand the current epidemiological situation, we analyzed the virologic data of wild poliovirus type 1 (WPV1) strains detected in Pakistan during 2013-2015. RESULTS: Five genetic clusters (A-E) were identified with at least 5% nucleotide divergence in the viral protein 1 (VP1) coding region. Peshawar, Quetta, and Karachi were found to be the major endemic foci where multiple discrete genetic lineages of WPV1 were detected. Phylogenetic analysis suggests that wild poliovirus strains from endemic regions were genetically distant (with 5%-15% VP1 nucleotide divergence) from those detected in North Waziristan cases, excluding the possibility of a recent progenitor of WPV1 instigating single-source transmission across the country. Orphan lineages detected in Rawalpindi, Lahore, Hyderabad, Sukkur, and Jacobabad revealed silent transmission and the need for vigilant surveillance. Sustenance of analogous genetic lineages over a period of 3 years highlights multiple unimmunized foci present to maintain viral genetic diversity. CONCLUSIONS: Our findings are inconsistent with the hypothesis that impoverished populations from North Waziristan serve as a possible determinant of widespread poliomyelitis infection in Pakistan and further emphasize the need to scale-up clinical and environmental surveillance as well as immunization activities.
Authors: Radboud J Duintjer Tebbens; Mark A Pallansch; Stephen L Cochi; Derek T Ehrhardt; Noha H Farag; Stephen C Hadler; Lee M Hampton; Maureen Martinez; Steve G F Wassilak; Kimberly M Thompson Journal: Risk Anal Date: 2018-01-03 Impact factor: 4.000
Authors: Kathleen M O'Reilly; Robert Verity; Elias Durry; Humayun Asghar; Salmaan Sharif; Sohail Z Zaidi; M Zubair M Wadood; Ousmane M Diop; Hiro Okayasu; Rana M Safdar; Nicholas C Grassly Journal: BMC Infect Dis Date: 2018-04-13 Impact factor: 3.090
Authors: Natalie A Molodecky; Isobel M Blake; Kathleen M O'Reilly; Mufti Zubair Wadood; Rana M Safdar; Amy Wesolowski; Caroline O Buckee; Ananda S Bandyopadhyay; Hiromasa Okayasu; Nicholas C Grassly Journal: PLoS Med Date: 2017-06-12 Impact factor: 11.069
Authors: Dominika A Kalkowska; Mark A Pallansch; Stephen L Cochi; Kimberly M Thompson Journal: Open Forum Infect Dis Date: 2021-05-23 Impact factor: 3.835
Authors: Steve J Kroiss; Maiwand Ahmadzai; Jamal Ahmed; Muhammad Masroor Alam; Guillaume Chabot-Couture; Michael Famulare; Abdirahman Mahamud; Kevin A McCarthy; Laina D Mercer; Salman Muhammad; Rana M Safdar; Salmaan Sharif; Shahzad Shaukat; Hemant Shukla; Hil Lyons Journal: PLoS One Date: 2018-12-28 Impact factor: 3.240