Avian Influenza:A Zoonotic Disease of International

Importance

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WHAT IS INFLUENZA?

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What is influenza?

• Influenza (or the flu) is a disease caused by a VIRUS

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What are the symptoms of influenza?

Once people are infected with an influenza virus, they can develop the following symptoms:– Fever– Cough– Sore throat– Stuffy nose– Body aches– Headaches– Fatigue (very tired)– Some people may have vomiting and diarrhea, although this is

more common in children than adults.

Vaccinations are available to help prevent you from being infected with influenza.

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What is a virus?

• What is a virus?– An infectious

agent that can replicate only INSIDE a HOST CELL

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What are the names of some common viruses?

•Rabies virus•Influenza virus

How big is a virus?

• If a human cell were the size of the SUN, a virus would be about the size of the EARTH!

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What does a virus look like?

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Common cold

RABIES

POLIO

What does a virus look like?

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Attachment MoleculesProtein coat

Genetic Material

SPREAD OF INFLUENZA

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Seasonal epidemic influenza

• An epidemic occurs when substantially more cases of a disease (such as the flu) occur in a place during a certain time period than would normally be expected.

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Pandemic influenza

• A pandemic is an epidemic of infectious disease (such as influenza) that affects populations across a large region.

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How is influenza spread?

• Influenza spreads easily from person to person through coughing and sneezing.

• Influenza is also spread by touching an infected person or an item contaminated with the virus and then touching your eyes, nose, or mouth.

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Why you should cover your mouth when you sneeze!

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Some influenzas are more dangerous than others!

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Versus

Influenza viruses

Influenza viruses are of three main types: – A viruses

• Infect birds and other animals as well as humans• Are a source of seasonal influenza epidemics and all pandemics

– B viruses• Infect humans only and do not cause pandemics (can cause

epidemics, but generally less severe than “A”)

– C viruses• Infect humans and swine (pigs) and do not cause pandemics• Usually cause only mild disease

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HISTORICAL OUTBREAKS

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1918—Spanish flu

This outbreak caused 20-40 million deaths worldwide.– 675,000 Americans died during this outbreak.– 43,000 U.S. soldiers died during this outbreak.

During World War I, this outbreak was called the Spanish flu mainly because the pandemic received more attention in the news after it moved from France to Spain in November 1918.

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1918—Spanish flu

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Other influenza pandemics

• 1957- Asian flu– 1 million deaths worldwide– Approximately 70,000 U.S. deaths

• 1968- Hong Kong flu– 1 million deaths worldwide

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AVIAN INFLUENZA

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Avian influenza

• “Avian influenza”– Means influenza A viruses that occur naturally in

wild water birds– Can spread to people and other types of animals

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Bar-headed Geese

Why are some influenzas more severe than others?

Avian influenza viruses are classified by surface molecules on the virus.◦Hemagglutinin (H)

H1-H16 Sites for attachment to infect cells of the host (for

example, bird or person)

◦Neuraminidase (N) N1-N9 Assists in the release of newly formed virus particles from

the surface of an infected cell

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Why are some influenzas worse than others?

• Viruses with certain combinations of “H” and “N” cause more severe disease in both people and poultry (for example, chickens).

• These viruses are called highly pathogenic avian influenza (HPAI) viruses

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Avian influenza (H5N1)• A highly pathogenic avian influenza virus (H5N1) first

showed up in Hong Kong in 1997. This virus is now circulating in birds in many countries in Asia and the Middle East.

• This influenza virus is very dangerous to domestic poultry (for example, chickens). This virus and can also make people very sick.

• So far, the virus doesn’t spread very easily from person to person. However, people can become sick after contacting an infected bird.

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Avian influenza (H5N1)

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• What do you think would happen if one of these chicks got sick with H5N1 avian influenza?

Avian influenza (H5N1)

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How is H5N1 avian influenza spread from birds to humans?

Spread of H5N1 avian influenza

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• H5N1 avian influenza can be spread by inhaling dried bird droppings.

Spread of H5N1 avian influenza

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• H5N1 avian influenza can spread through the butchering process and handling of infected birds.

Spread of H5N1 avian influenza

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• Remember that H5N1 avian influenza DOES NOT spread easily between humans like the seasonal flu.

How do you stop the spread of H5N1 avian influenza?

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• One solution is to get rid of all of the poultry (for example, chickens) that might be infected.

How do you stop the spread of H5N1 avian influenza?

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• We can also stop the spread of H1N1 avian influenza by providing protection for poultry workers, including:– Mask– Gloves– Eye shield– Disposable suit

Why is H5N1 avian influenza important?

• The danger is that avian influenza viruses change very frequently.– Humans can’t transmit the current H1N1 avian influenza

between themselves very well.– However, the virus could change into a form that could be

transmitted between people. – If this happened, the virus could cause a global pandemic

with lots of people becoming sick.

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Do we have H5N1 avian influenza in the USA?

• No, we currently don’t have H5N1 avian influenza in the USA.

• However, in the USA some influenzas with other “H” and “N” combinations have killed poultry and severely affected people.

• The US government is very careful about monitoring influenza viruses and quickly making efforts to eliminate dangerous virus forms.

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Conclusions

• Influenza viruses cause the flu.

• Influenza viruses are spread from person to person by coughing and sneezing.

• Avian influenza viruses occur naturally in birds, but can sometimes be transmitted to humans and other animals.

• Highly pathogenic avian influenza viruses can be very dangerous to poultry and humans.

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