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 % 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

YearSubtypeSourceResult 1918 H1N1 Spanish Flu Swine & Birds million death 1957 H2N2 Asian FluHuman & Birds >2 million excess mortality 1968 H3N2 Hong Kong FluHuman & Birds 1 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 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

Total Country deathscasesdeathscasesdeathscasesdeathscasesdeathscasesdeathscasesdeathscases Azerbaijan Cambodia China Djibouti Egypt Indonesia Iraq Lao People's Democratic Republic Myanmar Nigeria Pakistan Thailand Turkey Viet Nam Total 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

 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 HaemagglutininNeuraminidase 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 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

Birds and Water Fouls: (e.g. Ducks, geese) Natural carrier of avian flu, can be symptomatic or asymptomatic Chicken New to H5N1 virus Invariable fatal when attacked Pigs Avian 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 Human Feline Feline (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 Flu Avian Flu Reassortment It is important to remember that H1 & H3 viral subtypes are prevalent in pigs Method 2

2008Avian Flu19

 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 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

Pandemic Pandemic ： 2008 Health care overburdened Health care system rapidly overburdened Social 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. Efficient human to human transmission 2008 SUMMARY:

2008