Avian Influenza - Pandemic Threat ?Reinhard Bornemann

1918

1918: Invasion of the US in 4 weeks

• animierte Ausbreitungskarte:

• http://www.pbs.org/wgbh/amex/influenza/maps/index.html

1918: special features

• rapid spread

• high attack rate

• unusually high morbidity and mortality in young adults

Influenza pandemics in history

Year Subtype Deaths

1889/90 H2? H3? 1 Mio.

1918/19 H1N1 50 Mio.

1957/58 H2N2 1-2 Mio.

1968/69 H3N2 1 Mio.

since 1977 H1N1 ?

Viral replication cyclus

Antigenic drift

The „flu alphabet“

• 8 genome segments, most important:• Hemagglutinin HA (16 subtypes, H1-16) • Neuraminidase NA (9 subtypes, N1-9)

• A / Fujian / 411 / 02 (H3N2)• A / Hong Kong / 156 / 97 (H5N1)• A / (animal) / (place) / (no.) / (year) (HxNx)

Pandemic threat:assessment methods

• virological / immunological• potential of mutation / reassortment

• epidemiological• conditions for an emerging pandemic

Virological view I

• animal to human infection• attenuation in human host• transmissibility between humans• enhanced virulence

Virological view II

• recently high spread of avian flu in Asia, moving west

• since 1997, especially 2004, increasing human infections

• increasing and interacting human and animal populations

• increasing warnings of specialists and officials

Epidemiological view

• transmissibility, infectiosity• incubation time, duration of infectiosity• „herd immunity“ after earlier epidemics ? (N2 /

1968 vs. N2 / 1957 ?• effect of prior vaccination to „human“ flu ?• living conditions: home, work, social contacts• demography ?• mobility: local, regional and international• others, as vectors, surrounding conditions ?

Control measures ?

• ...

• ...

• ...

Control measures

• responsible institutions• „pandemic plans“• education of health professionals• education of general population• vaccination• antiviral treatment• isolation• contact tracing• mobility reduction (other ...)

Vaccination

• interpandemic flu vaccination cycle

• scenario for pandemic vaccination

Treatment

• amantadine

• neuraminidase inhibitors:

• Oseltamivir, Zanamivir

Mathematical modelling

• ...

Modelling of flu epidemics

• Ferguson, N.M., et al.:• Strategies for containing an emerging

influenza pandemic in Southeast Asia• Nature online 3 August 2005

• Longini, I.M., et al:• Containing Pandemic Influenza at the Source• Science 309: 1083-87 (August 2005)

Modelling parameters

• R0:• number of secondary infected cases

• Theta (:• proportion of transmission before onset of

clinical symptoms

• Tg:• disease generation time

Sources

• http://www.uni-bielefeld.de/gesundhw/ag2/infepi/• Erkrankungsbilder > Influenza• Historisches > 1918