Avian Influenza AH5N1Bird Flu

Avian Influenza A (H5N1)“Bird Flu”

Etiology


Viral diseaseAvian Influenza (HPAI)H5 and H7 – highly pathogenicHuman case fatality estimated to be as high has 50%, but not definitely known

Shore birds

Pandemic disease cycle
Natural avian influenza cycle
Mammals (primarily swine)
Waterfowl
Domestic birds
Humans
Direct bird to human transmission is also common



Cycle of Avian Influenza viruses in animals & humans

WHO Pandemic Alert Phase Plan

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS

Map of current outbreak

40-100M
Worst case potential global deaths
2-7M
Best case global deaths in pandemic
1
Bird flu that can be fatal to humans
15
Known bird flu types
2
Types of potential antivirals for bird flu
1.6B
Est. international airline passengers yearly
12
Number of countries affected (since Dec 04)
2
Suspected human-to-human transmissions
64
Human deaths
125
Human cases since date of onset (12/26/03)
*Source: World Health Organization

Bird flu by the numbers

First case of bird flu in the U.S.

Human H5N1

Incubation: 3-5 days Few URI symptoms Severe viral pneumonia picture Fever Lymphopenia Pulmonary infiltrates Hypoxia Diarrhea (50%) Time to death: 10 days (mean)

Transmission

Respiratory droplets vs. aerosol Hand to hand Fomites Viral shedding starts 24 hours before clinical illness and lasts 5-7 days

Prerequisites for a pandemic

Novel virus with no immunity Able to cause significant disease in humans Efficient human to human transmission Re-assort during co-infection with H3N2 Evolve in a human by spontaneous mutation

Common pandemic features

Herald wave (warning): up-tick in mortality at end of prior year Increased mortality Mortality shift to younger ages Multiple waves of increased mortality for several years

Potential for influenza pandemics

All influenza viruses can mutate Avian flu can cause illness in humans Little to no herd immunity to avian strains among humans If avian viruses acquire human genes Facilitate efficient person-to-person transmission H5N1 of particular concern No one can predict when a pandemic might occur

How is bird flu in humans treated?

The H5N1 virus currently infecting birds in Asia that has caused human illness and death is resistant to amantadine and rimantadine Neurominidase inhibitors oseltamavir (Tamiflu) zanamavir (Relenza) inhaled, not stocked in house Resistance can develop Additional studies are needed to prove the effectiveness of these medicines.

Defenses

Vaccination Prophylaxis Rapid diagnosis Treatment Infection control Respiratory etiquette Hand washing Disinfection Droplet precautions in hospitals

CDC recommendations

Enhanced surveillance in the U.S. of H5N1. Travelers to countries with known outbreaks of influenza A (H5N1) should avoid: Poultry farms Contact with animals in live food markets Surfaces that appear to be contaminated with feces from poultry or other animals. CDC does not recommend any travel restrictions to affected countries at this time. For more information, visit Travelers' Health