Emergence and Localized Circulation of a Vaccine-Derived Poliovirus in an Isolated Mountain Community in Guangxi, China

Autor: Dongyan Wang, Wenbo Xu, Jaume Jorba, Yong Zhang, Lin Huang, Junjing An, Shuangli Zhu, Olen M. Kew, Dongmei Yan, Ge Zhong, Xiaofeng Liang, Wei Liu, Li Li, Ning Wen
Rok vydání: 2010
Předmět:
Zdroj: Journal of Clinical Microbiology. 48:3274-3280
ISSN: 1098-660X
0095-1137
Popis: Circulation of indigenous wild poliovirus (WPV) ceased in China in 1994 (23, 38, 44). High levels of population immunity have been maintained throughout most of the country, and vigorous immunization responses to the detection of poliovirus circulation have subsequently protected against widespread poliovirus transmission. The WPVs (WPV type 1 [WPV1] and WPV3), introduced into communities bordering Myanmar in 1995 and 1996, were associated with only four paralytic poliomyelitis (polio) cases (44), and WPV1 imported into Qinghai, China, from northern India was associated with only one case in 1999 (45) Keys to the success in China are (i) a strong routine immunization program with trivalent oral poliovirus vaccine (tOPV) supplemented by synchronized mass campaigns in the form of national immunization days (NIDs) and subnational immunization days (SNIDs) (38), (ii) sensitive surveillance for cases of acute flaccid paralysis (AFP) (47), and (iii) rapid, detailed characterization of poliovirus isolates (23, 47). The eradication of polio in China (40), whose population constitutes 23% of the world population, provided strong impetus to the World Health Organization's (WHO's) Global Polio Eradication Initiative, whose efforts have reduced the polio incidence by >99% since 1988, such that only four countries have never stopped WPV circulation (43). Successful eradication of WPV, however, does not entirely eliminate risks of paralytic poliomyelitis. The primary weapon in polio eradication, OPV, is genetically unstable and can revert to increased neurovirulence during replication in the human intestine (19, 27, 35). Consequently, in all countries where OPV is used, there is a very low background rate of vaccine-associated paralytic poliomyelitis (VAPP) among OPV recipients and their close contacts (35). Exposure to OPV of persons with primary immunodeficiencies is associated with an ∼3,000-fold higher VAPP risk (36) and the further risk of prolonged infection with immunodeficiency-associated vaccine-derived polioviruses (iVDPVs) (19). An additional risk is the emergence and spread of circulating VDPVs (cVDPVs) in areas with low rates of OPV coverage (19). cVDPV outbreaks have occurred and been controlled in Egypt (46), Hispaniola (Haiti and the Dominican Republic) (18), the Philippines (34), Madagascar (32), Indonesia (13), Cambodia (10), Myanmar (10), and China (23). Within the past year, cVDPV outbreaks have occurred in Nigeria (type 2, 2005 to 2010), the Democratic Republic of Congo (type 2, 2008 to 2010), Ethiopia (type 2, 2008 to 2009; type 3, 2009 to 2010), Somalia (type 2, 2008 to 2009), and India (type 2, 2009 to 2010) (9) (for updates, see http://www.polioeradication.org/content/general/cvdpv_count.pdf). VDPVs are operationally defined as having >1% nucleotide sequence divergence from their parental Sabin strains in the VP1 capsid region (9, 19). In addition to the well-defined cVDPV and iVDPV categories, VDPV isolates are assigned to a third category, ambiguous VDPVs (aVDPVs), when there is no evidence of community circulation or immunodeficiency (9). Since 1997, an average of one to two new VDPV isolates has been identified each year in China (23). The first cVDPV outbreak in China (three cases, four contacts), associated with type 1 virus, occurred in Guizhou Province in 2004 (23). The first reported iVDPVs (types 2 and 3) were isolated in Anhui Province in 2005 from a patient with X-linked agammaglobulinemia (10). In 2007, four aVDPVs were isolated from four patients and one was isolated from one healthy child in 2009. From March to May 2006, type 1 VDPV was isolated from one AFP case and six healthy contacts within two neighboring mountain villages in the Guangxi Zhuang Autonomous Region of southern China. An important local risk factor for VDPV emergence was the low rate of OPV coverage among children 5 to 10 years of age. Although these isolates were originally classified as aVDPVs according to WHO criteria because only a single AFP case attributable to VDPV was found (8, 10), the sequence relationships among these isolates were consistent with cVDPV circulation for ∼12 months after the initiating OPV dose. No VDPVs were detected in other villages with similar immunization status, suggesting that the cVDPV transmission was highly localized. In this report, we describe the epidemiological and virological investigations of the Guangxi cVDPV infections and discuss the factors that may have favored its emergence and localized transmission.
Databáze: OpenAIRE
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