Reemergence of recombinant vaccine-derived poliovirus outbreak in Madagascar.
BACKGROUND
After the 2001-2002 poliomyelitis outbreak due to recombinant vaccine-derived polioviruses (VDPVs) in the Toliara province of Madagascar, another outbreak reoccurred in the same province in 2005.


METHODS
We conducted epidemiological and virological investigations for each polio case patient and for their contacts.


RESULTS
From May to August 2005, a total of 5 cases of acute flaccid paralysis were reported among unvaccinated or partially vaccinated children 2-3 years old. Type-3 or type-2 VDPV was isolated from case patients and from healthy contacts. These strains were classified into 4 recombinant lineages that showed complex mosaic genomic structures originating from different vaccine strain serotypes and probably from human enterovirus C (HEV-C) species. Genetic relatedness could be observed among these 4 lineages. Vaccination coverage of the population was very low (<50%).


CONCLUSIONS
The broad distribution of VDPVs in the province and their close genetic relationship indicate intense and rapid cocirculation and coevolution of the vaccine strains and of their related HEV-C strains. The occurrence of an outbreak due to VDPV 3 years after a previous outbreak indicates that a short period with low vaccination coverage is enough to create favorable conditions for the emergence of VDPV in this setting.
Rakoto-Andrianarivelo
Mala
M
Unité de Virologie, Institut Pasteur de Madagascar, Madagascar. mala@pasteur.mg
Gumede
Nicksy
N
Jegouic
Sophie
S
Balanant
Jean
J
Andriamamonjy
Seta N
SN
Rabemanantsoa
Sendraharimanana
S
Birmingham
Maureen
M
Randriamanalina
Bakolalao
B
Nkolomoni
Léon
L
Venter
Marietjie
M
Schoub
Barry D
BD
Delpeyroux
Francis
F
Reynes
Jean-Marc
JM
D002675:Child, Preschool; D004196:Disease Outbreaks; D030015:Enterovirus C, Human / Q000235:genetics; D006801:Humans; D008270:Madagascar / Q000453:epidemiology; D008297:Male; D010802:Phylogeny; D011051:Poliomyelitis / Q000453:epidemiology* / Q000821:virology; D017955:Poliovirus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D023321:Poliovirus Vaccines / Q000009:adverse effects* / Q000302:isolation & purification; D012367:RNA, Viral / Q000235:genetics; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D014614:Vaccines, Synthetic / Q000009:adverse effects
D023321:Poliovirus Vaccines; D012367:RNA, Viral; D014614:Vaccines, Synthetic