Importation and circulation of poliovirus in Bulgaria in 2001.
OBJECTIVE
To characterize the circumstances in which poliomyelitis occurred among three children in Bulgaria during 2001 and to describe the public health response.


METHODS
Bulgarian authorities investigated the three cases of polio and their contacts, conducted faecal and serological screening of children from high-risk groups, implemented enhanced surveillance for acute flaccid paralysis, and conducted supplemental immunization activities.


RESULTS
The three cases of polio studied had not been vaccinated and lived in socioeconomically deprived areas of two cities. Four Roma children from the Bourgas district had antibody titres to serotype 1 poliovirus only, and wild type 1 virus was isolated from the faeces of two asymptomatic Roma children in the Bourgas and Sofia districts. Poliovirus isolates were related genetically and represented a single evolutionary lineage; genomic sequences were less than 90% identical to poliovirus strains isolated previously in Europe, but 98.3% similar to a strain isolated in India in 2000. No cases or wild virus isolates were found after supplemental immunization activities were launched in May 2001.


CONCLUSIONS
In Bulgaria, an imported poliovirus was able to circulate for two to five months among minority populations. Surveillance data strongly suggest that wild poliovirus circulation ceased shortly after supplemental immunization activities with oral poliovirus vaccine were conducted.
Kojouharova
Mira
M
Department of Epidemiology, National Center for Infectious and Parasitic Diseases, Sofia, Bulgaria.
Zuber
Patrick L F
PL
Gyurova
Snejana
S
Fiore
Lucia
L
Buttinelli
Gabriele
G
Kunchev
Angel
A
Vladimirova
Nadejda
N
Korsun
Neli
N
Filipova
Radosveta
R
Boneva
Roumiana
R
Gavrilin
Eugene
E
Deshpande
Jagadish M
JM
Oblapenko
George
G
Wassilak
Steven G
SG
D000914:Antibodies, Viral / Q000097:blood; D002031:Bulgaria / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks / Q000517:prevention & control*; D005243:Feces / Q000821:virology; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D032541:Mass Vaccination; D008913:Minority Groups; D011051:Poliomyelitis / Q000453:epidemiology* / Q000517:prevention & control; D017955:Poliovirus / Q000302:isolation & purification; D011055:Poliovirus Vaccine, Oral / Q000600:supply & distribution*; D011159:Population Surveillance; D006178:Romani People; D012959:Socioeconomic Factors
D000914:Antibodies, Viral; D011055:Poliovirus Vaccine, Oral