Epidemic vs. Pandemicoccurs when an

infectious disease spreads rapidly to many people. In 2003, the severe acute respiratory syndrome (SARS) epidemic took the lives of nearly 800 people worldwide.

a global disease outbreak; HIV is an example of

one of the most destructive

global pandemics in history.

PandemicsAn influenza pandemic occurs when:• A new subtype of virus arises, and

humans have little or no immunity to it. Everyone is at risk.

• The virus spreads easily from person to person, such as through sneezing or coughing.

• The virus begins to cause serious illness worldwide. With past flu pandemics, the virus reached all parts of the globe within six to nine months. With the speed of air travel today, public health experts believe an influenza pandemic could spread much more quickly.

2009

Causative AgentInfluenza A virus subtype AH1N1,or commonly known as AH1N1 or

swine flu

Causative AgentInfluenza can be classified as A, B,

or C

A – found in many kinds of animals, including ducks,

chickens, pigs, and whales, and also humans

B – widely circulates in humansC – found in humans, pigs, and dogs and causes mild respiratory

infections, but does not spark epidemics

Causative AgentInfluenza A virus is the most

dangerous of the three.

Influenza A is categorized into subtypes based on the 2 proteins

on the surface of the viral envelope:

H – hemagglutininN – neuraminidase

Naming: Influenza type A subtype HxNx

SymptomsMild illness, fever, severe

headache, body aches, sorethroat, cough, runny nose and

occasionally vomiting and diarrhea

HOW TO DISTINGUISH FROM ALLERGY or ORDINARY FLU

Muscle pain, fever, vomiting

Pathogenesis: OriginA novel and emerging disease

It has two genes from flu viruses that normally circulate in pigs in Europe and Asia, and bird (avian)

genes and human gene

Waterfowl (bird) + swine in Europe/Asia + swine in US +

human

Pathogenesis: Transmission

When an infected person coughs or sneezes near a susceptible person,

transmission occursRequires close contact between the

infected and recipient persons because droplets do not remain

suspended in the air and travel short distances not more than 6 feet

Contact with contaminated surface: may become infected by touching

something with flu viruses on it and then touching their mouth or nose

Pathogenesis: InvasionInfection: upper part of the respiratory

system

The hemagglutinin molecule has to be cut by enzymes in the body before it

can enter human cells. Once cut, virus affects cells, causing the

expression of the disease (symptoms such as sore throat occurs). This virus has a single cleavage site

where this happens, causing only a mild infection in the respiratory tract

H1N1 does not invade other tissues outside the upper respiratory tract

VectorsPigs and humans: the swine flu virus can be directly transmitted from pigs to humans, humans to humans, or humans to pigs. But despite the name of the virus, one cannot catch AH1N1 from eating bacon, ham, or any other pork products.

Incubation PeriodThe incubation period of the

influenza A (H1N1) strain, now estimated at about 1 to 5 days, is shorter and more like seasonal influenza than originally thought, according to the World Health Organization (WHO).

Virulence FactorsVirulence factor: H1 and N1

The swine virus in 2009 was not more virulent than seasonal strains as it lacked an important molecular signature (the protein PB1-F2). This protein was present in the 1918 virus as well as the highly lethal H5N1 chicken virus. In reference to the common seasonal flu, it retained its virulence factors by its ability to rapidly evolve by antigenic shift/drift.

H1N1 vs. Seasonal Flu

The new H1N1 swine flu virus emerged in the spring of 2009. It is a novel virus, meaning that it is an infectious agent that humans have never been infected with. The seasonal flu is most threatening to those with weak immune systems, such as the very young and old, while the novel H1N1 virus appears to be a threat to healthy, young adults.

H1N1(Swine Flu) vs. H5N1(Bird Flu)

Both are influenza A viruses but different haemagglutinin (H) and neuraminidase (N).

EpidemiologyIn 1918 – pandemic Spanish Flu

First cases in US, January 1918Infected 500 billion, more than

10% of which died

EpidemiologyWW1 Allies named it Spanish Flu since it gained greater press attention after it moved from France to Spain

Epidemiology2009 - pandemic Influenza A (H1N1)

Return of the H1N1 virus Mexico, March-April 2009 then in US,

and other countries June 2009 - WHO declared widespread

on at least two continents H1N1 virus declared Phase 6 by WHO

at August 2009 (pandemic) Said to be over in August 2010 In the Philippines, first case was a 10-

year old Filipina who returned from USA and Canada on May 18, 2009

EpidemiologyAs of 2013, AH1N1 is still existent and

is concentrated on the South American and African countries.

As an emerging disease...

Spreads rapidly (epidemic and pandemic)

Novel disease combination of different flu virus

types (bird + swine + human gene)

Diagnosis• Very similar to

seasonal influenza, only with vomiting, diarrhea and severe muscle pains

• Laboratory test to identify influenza A (H1N1) virus

• In the Philippines, the first case was confirmed via throat specimen testing

TreatmentTake antiviral medications as

prescribed by doctor

Treatment• Stay in bed to recover (self-

quarantine)

Prevention• Maintain proper

hygiene (washing of hands for 10-20 seconds with detergent soap kills H1N1 virus)

• Increase body’s resistance

• Take flu shots (as prescribed by doctor)

Prevention• Avoid close contact with infected

people• Wear face masks• Vaccine for influenza A virus

QUESTIONS