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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