The New Influenza A/H1N1

Isabelle Thomas May 28-29, 2009 Brussels

,

HA

SCIENCE VOL 324 15 MAY 2009

Influenza virus Famille Orthomyxoviridae…….Genus Influenza (80-100 nm)

• 8 RNA segments• 2 Surface glycoproteins (HA, NA)

• 3 Types (A, B, C)

Human : type A and B H1N1, H3N2, B,…

Wild bird: type Aall subtypes, 16H, 9N

Swine : Type AH1N1, H3N2 , H1N2, ……

HA

NA

Reassortant

Human Pandemic influenza viruses: reassortment is postulated to have occurred in pigs

Influenza Viruses: Continuous evolutionAntigenic “drift”: Point mutations in the hemagglutinin gene cause minor antigenic changes to HA.

Antigenic “drift” causes seasonal epidemics

Nucleotide Substitutions (x100)

0

2.8

2

A/Belgium/192/07A/Belgium/198/07A/Belgium/189/-07A/Belgium/209/-07A/Belgium/203/07A/Belgium/194/07A/Belgium/146/-07A/Belgium/124/07A/Belgium/122/07

A/Belgium/945/-07A/Belgium/953/-07

A/Belgium/917/-07A/Belgium/946/07A/Belgium/963/07

A/Belgium96/07A/Belgium/139/07A/Belgium/141/07A/Belgium/140/07

A/Belgium/144/07A/Belgium/919/07A/Belgium/959/-07A/Belgium/114/07A/Belgium/916/-07A/Belgium/930/07A/Belgium/931/-07

A/Belgium/206/07

A/Wisconsin/67/ 2005 A/California/7/2004

A/Fujian/ 411/ 2002 A/Wyoming/3/ 2003

H3N2

Influenza viruses : Continuous evolution

Antigenic “shift”: Emergence of a new human influenza A virus subtype (new HA subtype +/- NA).

Little or no immunity pandemic risk

Surveillance National : National Influenza Centers (NIC) European : EISS, ECDC International : WHO

ObjectivesTo monitor influenza activity

To determine types and subtypes of the circulating strains

To characterize circulating strains (Antigenic and Genetic characterization)

To contribute to the annual determination of the influenza vaccine content

To monitor resistance to antiviralsTo be able to detect any new human influenza virus : ex A/H7N7,

A/H5N1,

Surveillance of Influenza viruses :

WHO Alert : 26 AprilNew virus A/H1N1 of swine origin

Cases in Mexico Cases in USA

Characteristics Typable Real time PCR AUnsubtypable Real time PCR H1 seasonal

Sequences of new strains rapidly available

Development of real time PCR specific for SWH1N1

Surveillance of Influenza viruses :

Comparison of H1N1 Swine Genotypes in Recent Cases in the United States

Novel Swine-Origin Influenza A (H1N1) Virus Investigation Team. N Engl J Med 2009;10.1056/NEJMoa0903810

H1 from American swine (>6% divergent)

N1 & M from Eurasian swine

PB1 from human originPA & PB2 from avian originNP & NS from American swine

H5N1

New H1N1

• More than 8000 confirmed cases in 40 countries• 74 reported death • Most cases seem to be mild and self-limited• The virus is transmitted easily from person-to-person• Countries have rapidly developed important diagnostic

capacity

In Belgium

Real Time PCR A, SWH1, SWA

150 suspected cases8 positive swH1N1 cases

5 patients coming back from the USA3 close contact from one of the patients

Current situation

With Influenza viruses nothing can be predicted

• How Fast will the virus spread throughout the world?

• Will it become widely established?

• Will the infectivity and virulence of the virus change over time?

Evolution

Acknowledgments

Virology C. Gérard Ch. Van den Poel M. Abady I. Fdillate I. Micalessi B. Brochier D. Bauwens Y. Ronflette

Epidemiology S.Quoilin F.Wuillaume