Novel virus influenza A (H1N1sw) in South-Eastern France, April-August 2009.
BACKGROUND
In April 2009, the first cases of pandemic (H1N1)-2009 influenza [H1N1sw] virus were detected in France. Virological surveillance was undertaken in reference laboratories of the seven French Defence Zones.


RESULTS
We report results of virological analyses performed in the Public Hospitals of Marseille during the first months of the outbreak. (i) Nasal swabs were tested using rapid influenza diagnostic test (RIDT) and two RT-PCR assays. Epidemiological characteristics of the 99 first suspected cases were analyzed, including detection of influenza virus and 18 other respiratory viruses. During three months, a total of 1,815 patients were tested (including 236 patients infected H1N1sw virus) and distribution in age groups and results of RIDT were analyzed. (ii) 600 sera received before April 2009 and randomly selected from in-patients were tested by a standard hemagglutination inhibition assay for antibody to the novel H1N1sw virus. (iii) One early (May 2009) and one late (July 2009) viral isolates were characterized by sequencing the complete hemagglutinine and neuraminidase genes. (iiii) Epidemiological characteristics of a cluster of cases that occurred in July 2009 in a summer camp were analyzed.


CONCLUSIONS
This study presents new virological and epidemiological data regarding infection by the pandemic A/H1N1 virus in Europe. Distribution in age groups was found to be similar to that previously reported for seasonal H1N1. The first seroprevalence data made available for a European population suggest a previous exposure of individuals over 40 years old to influenza viruses antigenically related to the pandemic (H1N1)-2009 virus. Genomic analysis indicates that strains harbouring a new amino-acid pattern in the neuraminidase gene appeared secondarily and tended to supplant the first strains. Finally, in contrast with previous reports, our data support the use of RIDT for the detection of infection in children, especially in the context of the investigation of grouped cases.
Nougairède
Antoine
A
Unité Mixte de Recherche 190: Unité des Virus Emergents, Université de la Méditerranée et Institut de Recherche pour le Développement, Marseille, France.
Ninove
Laetitia
L
Zandotti
Christine
C
Salez
Nicolas
N
Mantey
Karine
K
Resseguier
Noémie
N
Gazin
Céline
C
Raoult
Didier
D
Charrel
Rémi N
RN
de Lamballerie
Xavier
X
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000367:Age Factors; D000368:Aged; D000914:Antibodies, Viral / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000145:classification / Q000235:genetics* / Q000276:immunology; D007251:Influenza, Human / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D010802:Phylogeny; D015995:Prevalence; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012621:Seasons; D017422:Sequence Analysis, DNA; D019562:Viral Load; D055815:Young Adult
D000914:Antibodies, Viral