2008 Avian Flu 1

• Avian influenza is an infection caused by (bird) influenza viruses naturally occurring among birds.

• Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them.

• Infected birds shed influenza virus in their saliva, nasal secretions, and feces. Susceptible birds become infected when they have contact with contaminated secretions or excretions or with contaminated surfaces from infected birds. 2008

• Infection in domestic poultry causes two main forms of disease that are distinguished by low and high extremes of virulence :

a- The low pathogenic form may go undetected and usually causes only mild symptoms (such as ruffled feathers and a drop in egg production).

b-The highly pathogenic form spreads more rapidly through flocks of poultry. This form may cause disease that affects multiple internal organs and has a mortality rate that can reach 90-100% often within 48 hours.

2008

Endemic◦ stable pattern of occurrence of the disease.

Epidemic ◦ occurrence of the disease greatly in excess of the

expected rate.

Pandemic◦ worldwide spread of a disease, outbreaks or

epidemics occurring in many countries & in most regions of the world

2008

2008

Year Subtype Source Result

1918H1N1

Spanish FluSwine & Birds

40-50 million death

1957H2N2

Asian Flu Human & Birds>2 million excess

mortality

1968H3N2

Hong Kong Flu Human & Birds1 million excess

mortality

2008

WHO has reported human cases of avian influenza A (H5N1) in:

Countries:• Asia, Africa, the Pacific, Europe and the

Near East. Indonesia and Vietnam have reported the highest number of H5N1 cases to date.

• Overall mortality in reported H5N1 cases is approximately 60%.

• The majority of cases have occurred among children and adults aged less than 40 years old.

2008

• Mortality was highest in cases aged 10-19 years old.

• Studies have documented the most significant risk factors for human H5N1 infection to be direct contact with sick or dead poultry or wild birds, or visiting a live poultry market.

• Most human H5N1 cases have been hospitalized late in their illness with severe respiratory disease. A small number of clinically mild H5N1 cases have been reported.

2008

11 March 2008:• The Ministry of Health and Population of Egypt

has announced a new human case of avian influenza A(H5N1) virus infection. The case is an 8-year-old male from Etsa District, Fayum Governorate. He was hospitalized with symptoms on 3 March. He is receiving treatment and is in a stable condition.

• Investigations into the source of his infection indicate a history of contact with sick and dead poultry.

• Of the 47 cases confirmed to date in Egypt, 20 have been fatal.

2008

Country 

2003 2004 2005 2006 2007 2008 Total

cases deaths cases deaths cases deaths cases deaths cases deaths cases deaths cases deaths

Azerbaijan 0 0 0 0 0 0 8 5 0 0 0 0 8 5

Cambodia 0 0 0 0 4 4 2 2 1 1 0 0 7 7

China 1 1 0 0 8 5 13 8 5 3 3 3 30 20

Djibouti 0 0 0 0 0 0 1 0 0 0 0 0 1 0

Egypt 0 0 0 0 0 0 18 10 25 9 4 1 47 20

Indonesia  0 0 0 0 20 13 55 45 42 37 12 10 129 105

Iraq 0 0 0 0 0 0 3 2 0 0 0 0 3 2

Lao People's Democratic Republic 0 0 0 0 0 0 0 0 2 2 0 0 2 2

Myanmar 0 0 0 0 0 0 0 0 1 0 0 0 1 0

Nigeria 0 0 0 0 0 0 0 0 1 1 0 0 1 1

Pakistan 0 0 0 0 0 0 0 0 1 1 0 0 1 1

Thailand 0 0 17 12 5 2 3 3 0 0 0 0 25 17

Turkey 0 0 0 0 0 0 12 4 0 0 0 0 12 4

Viet Nam 3 3 29 20 61 19 0 0 8 5 4 4 105 51

Total 4 4 46 32 98 43 115 79 86 59 23 18 372 235

Total number of cases includes number of deaths.WHO reports only laboratory-confirmed cases. All dates refer to onset of illness.

Cumulative Number of Confirmed Human Cases of Avian Influenza A/(H5N1) Reported to WHO, 11 March 2008

• There are many different subtypes of type A influenza viruses. These subtypes differ because of changes in certain proteins on the surface of the influenza A virus (hemagglutinin [HA] and neuraminidase [NA] proteins).

• There are 16 known HA subtypes and 9 known NA subtypes of influenza A viruses. Many different combinations of HA and NA proteins are possible. Each combination represents a different subtype. All known subtypes of influenza A viruses can be found in birds.

• Usually, “avian influenza virus” refers to influenza A viruses found chiefly in birds, but infections with these viruses can occur in humans. The risk from avian influenza is generally low to most people, because the viruses do not usually infect humans.

2008

2008

Orthomyxoviridae

2 major antigenic glycoproteins: ◦ Haemagglutinin (HA) (H1-16)◦ Neuraminidase (NA) (N1-9)

Antigenic Drift◦ Change of genetic material due to lack of

proof-reading during replication ◦ Responsible for annual epidemic

Antigenic Shift◦ reassortment and merging of genetic

materials from different influenza strains◦ novel viral subtype, most human lack

immunity◦ Responsible for pandemics

2008

Influenza virus

Single-strand RNA with 8 gene segment

Haemagglutinin Neuraminidase

The Influenza Virion

2008 Avian Flu

H5N1 is of particular concern

Single-strand RNA with 8 gene segment

Haemagglutinin Neuraminidase

The H5N1 Virion

Influenza A H5N1 Virus

• Mutates rapidly

• Acquire genes from flu strains in other species

• Highly pathogenic in humans

• Birds, if surviving the infection, excrete the virus for 10 days, orally and in feces

However, confirmed cases of human infection from several subtypes of avian influenza infection have been reported since 1997.

• The spread of avian influenza viruses from one ill person to another has been reported very rarely, and has been limited, inefficient and unsustained.

• “Human influenza virus” usually refers to those subtypes that spread widely among humans. There are only three known A subtypes of influenza viruses (H1N1, H1N2, and H3N2) currently circulating among humans. It is likely that some genetic parts of current human influenza A viruses came from birds originally. Influenza A viruses are constantly changing, and they might adapt over time to infect and spread among humans.

2008

2008

Birds and Water Birds and Water FoulsFouls::(e.g. Ducks, geese)Natural carrier of avian flu, can be symptomatic or asymptomatic

ChickenChickenNew to H5N1 virusInvariable fatal when attacked

PigsPigsAvian flu in pigs are particularly worrisome as they possess bird flu and human flu receptors. They act as a reservoir for genetic reassortment for flu virus

HumanHuman

FelineFeline (Cats, Tigers and Leopards)

2008

Method 1

H5N1 virion

Affect water fouls & wild birds

Mutation

Affect domestic poultry like chicken

Mutation

Affect several mammalian species include felines, pigs, and human

2008

Human FluAvian Flu

Reassortment

It is important to remember that H1 & H3 viral subtypes are prevalent in pigs

Method 2

H1 N1H2 N2H3 N3H4 N4H5 N5H6 N6H7 N7H8 N8H9 N9

H10H11H12H13H14H15

Natural hosts of influenza viruses

Haemagglutinin subtype Neuraminidase subtype

2008Avian Flu 19

Of the few avian influenza viruses that have crossed the species barrier to infect humans, H5N1 has caused the largest number of detected cases of severe disease and death in humans.

However, it is possible that those cases in the most severely ill people are more likely to be diagnosed and reported, while milder cases go unreported.

2008

• Of the human cases associated with the ongoing H5N1 outbreaks in poultry and wild birds, more than half have died.

• Most cases have resulted from direct or close contact with H5N1-infected poultry or H5N1-contaminated surfaces.

• In general, H5N1 remains a very rare disease in people.

• The H5N1 virus does not infect humans easily, and if a person is infected, it is very difficult for the virus to spread to another person.

2008

Human health risks during the H5N1 outbreak :

• Because all influenza viruses have the ability to change, scientists are concerned that H5N1 virus one day could be able to infect humans and spread easily from one person to another.

• Because these viruses do not commonly infect humans, there is little or no immune protection against them in the human population.

• If H5N1 virus were to gain the capacity to spread easily from person to person, an influenza pandemic (worldwide outbreak of disease) could begin.

2008

Symptoms of avian influenza in humans have ranged from:

a- typical human influenza-like symptoms (e.g., fever, cough, sore throat, and

muscle aches) , b- eye infections, c- pneumonia, severe respiratory

diseases and d- other severe and life-threatening

complications. “The symptoms of avian influenza may

depend on which virus caused the infection”.

2008

The H5N1 virus that has caused human illness and death in Asia is resistant to amantadine and rimantadine, two antiviral medications commonly used for influenza.

Two other antiviral medications, oseltamivir and zanamivir, would probably work to treat influenza caused by H5N1 virus, but additional studies still need to be done to demonstrate their effectiveness.

2008

A small number of oseltamivir resistant H5N1 virus infections of humans have been reported.

Efforts to produce pre-pandemic vaccine candidates for humans that would be effective against avian influenza A (H5N1) viruses are ongoing.

However, no H5N1 vaccines are currently available for human use.

2008

The best protection against pandemic influenza—a vaccine that is well-matched to the virus causing illness—is not likely to be available at the outset of a pandemic.

 Community strategies that do not involve vaccines or medications (also called non-pharmaceutical interventions) may serve as a first line of defense to help delay or mitigate the spread of influenza.

2008

Cover the nose/mouth when coughing or sneezing

Perform hand hygiene if contact respiratory secretions and contaminated objects

Put on a surgical mask

2008Avian Flu

Respiratory hygiene and cough etiquette

• Use tissue paper to contain respiratory secretions and dispose in the waste receptacle

social distancing strategies to reduce contact between people

closing schools canceling public gatherings planning for liberal work leave policies teleworking strategies voluntary isolation of cases voluntary quarantine of household contacts

2008

PandemicPandemic ：

2008

Health careHealth care system rapidly overburdenedoverburdened

Social Disruption & PanicSocial Disruption & Panic

Impact of Pandemic

2008

Sporadic cases

No human-to-human

transmission

Sporadic cases

No human-to-human

transmission

Clusters of cases

Inefficient human-to-human

transmission

Clusters of cases

Inefficient human-to-human

transmission

On-going cluster related transmission

Substantial pandemic risk

On-going cluster related transmission

Substantial pandemic risk

Pandemic

Pandemic

1. Emergence of new Haemagglutinin subtype of

influenza A virus

2. General population have no or little immunity

3. Cause human disease in a high proportion of people

infected

4.4. Efficient human to human transmissionEfficient human to human transmission

2008

SUMMARY:

2008