Influenza: Facts and

prevention

By

Dr. Moustapha A. Ramadan

Objectives of the session

Epidemiology of influenza

Difference between influenza and

common cold

Virulence of influenza

Prevention of influenza

Influenza Virus Strains

Type A - moderate to severe illness- all age groups- humans and other animals

Type B- milder disease- primarily affects children- humans only

Type C- rarely reported in humans- no epidemics

Influenza Epidemiology

Reservoir Human, animals (type A only)

Transmission Contact (Direct-indirect-droplet)Airborne

Temporal pattern Peak December – March in temperate climateMay occur earlier or later

Incubation period 1-3 days

Communicability 1 day before to 5 days after onset (adults)

Influenza Virus

A/Fujian/411/2002 (H3N2)

Neuraminidase

Hemagglutinin

Type of nuclear

material

Virus

type

Geographic

origin

Strain

number

Year of

isolation

Virus

subtype

Species Infected by Influenza A,

HA and NA Subtypes

H15,16

H14

H13

H12

H11

H10

H3

H2

H1

H9

H8

H7

H6

H5

H4

N9

N8

N7

N6

N5

N3

N4

N2

N1

Influenza Antigenic Changes

Antigenic Shift

◦ major change, new subtype

◦ caused by exchange of gene segments

◦ may result in pandemic

Example of antigenic shift

◦ H2N2 virus circulated in 1957-1967

◦ H3N2 virus appeared in 1968 and completely

replaced H2N2 virus

Influenza Antigenic Changes

Antigenic Drift◦ minor change, same subtype◦ caused by point mutations in gene◦ may result in epidemic

Example of antigenic drift◦ in 2002-2003, A/Panama/2007/99 (H3N2)

virus was dominant◦ A/Fujian/411/2002 (H3N2) appeared in late

2003 and caused widespread illness in 2003-2004

Influenza Type A Antigenic Shifts

Year

1889

1918

1957

1968

1977

Subtype

H3N2

H1N1

H2N2

H3N2

H1N1

Severity ofPandemic

Moderate

Severe

Severe

Moderate

Mild

What are the symptoms of influenza in humans?

The symptoms of different forms of influenza in people tend to be similar and include

*Fever > 37.8°C

*Sore throat

*Cough

*Runny nose

*Chills

*Headache and body aches

*Fatigue

Some people have reported nausea, vomiting and diarrhea.

How is swine flu different from avian (bird)

flu?Avian flu so far has had difficulty infecting humans unless

they are exposed intensely to birds, because the virus

has not mutated in a way that makes it transmissible by

humans to other humans. Swine virus has origins

genetically from both pigs and birds, and the big

difference from the avian flu is that the swine virus can

be transmitted readily from human to human.

Is this just another scare that will go

away like bird flu?Bird flu is a theoretical threat and will need a

mutation to be able to be transmitted among

humans to become a serious threat.

There is logical concern that swine flu might

re-emerge next flu season.

Can influenza kill me?

Morbidity tends to be high and mortality low (1–

4%).

3-5 millions are affected yearly, 250 000-500 000

deaths yearly

We do not know all the factors geographically

and demographically that may contribute to the

mildness or severity of this flu.

What is the morbidity and mortality?

Avian flu H5 N1

Worldwide Total 505 Death 300 (59.4%)

Egypt Total 112 Death 36 ( 32.14%)

Swine flu H1 N1

Worldwide Total 8753967 Death 14346 (0. 16%)

Egypt Total 12230 Death 195 (1. 59%)

What are the preventive methods for me and contacts?

Proper hand hygiene

Coughing etiquette

Avoid overcrowded places

Avoid bad ventilated places

If you are ill, stay home.

Immunization

Surveillance by health authorities of the extent and progress of the outbreak and reporting of findings to the community is important.

What are the types of influenza vaccine

available?

There are two forms for influenza vaccine Inactivated Form and Live attenuated Form.

During any outbreak the influenza vaccine is made using the same process and facilities that are used to make the currently licensed seasonal influenza vaccines.

During outbreak people willing to have the vaccine should have both

The vaccine is usually available at fall.

Who will be covered by the vaccine ?

WHO currently estimates worldwide production capacity

for pandemic vaccines at approximately 3 billion doses

per year

These supplies will still be inadequate to cover a world

population of 6.8 billion people in which virtually

everyone is susceptible to infection

Vaccine supplies in low and middle income countries will

largely depend on donations from manufacturers and

other countries

Who is recommended to receive the

vaccine?

Infants younger than 6 months of age ;

Persons aged 65 years or older

Pregnant women

Persons of any age with certain chronic medical or immunosuppressive conditions and ,

Persons younger than 19 years of age who are receiving long-term aspirin therapy .

Healthcare personnel and emergency medical services personnel.

What are the side effects of vaccine?

In almost all vaccine recipients, symptoms are mild, self-

limited and last 1-2 days.

Side effects are expected to be similar to those observed

with seasonal influenza vaccines :

Local reaction at the injection site ( soreness, swelling,

redness)

Systemic reaction (fever, headache, muscle or joint

aches)

What medications are available for

influenza infections treatment/

chemoprophylaxis in humans?

There are four different antiviral drugs that are licensed

for use in the US for the treatment of influenza:

Amantadine, Rimantadine, Oseltamivir and

Zanamivir.

To whom chemoprophylaxis is

recommended?

Persons who are at higher risk for complications of influenza and are at close contact of a person with confirmed, probable, or suspected influenza during person’s infectious period.

Health care personnel, public health workers, or first responders who have had a recognized, unprotected close contact exposure to a person with confirmed, probable, or suspected influenza during person’s infectious period.

When chemoprophylaxis is not

considered?

Antiviral agents should not be used for post exposure chemoprophylaxis in healthy children or adults based on potential exposures in the community, school, camp or other settings .

Chemoprophylaxis generally is not recommended if more than 48 hours have elapsed since the last contact with an infectious person .

Chemoprophylaxis is not indicated when contact occurred before or after, but not during, the period of communicability.

What are the treatment

recommendations?

Early empiric treatment with antiviral drugs should be considered for persons with suspected or confirmed influenza who are at higher risk for complications including:

Children younger than 2 years old ;

Persons aged 65 years or older

Pregnant women

Persons of any age with certain chronic medical or immunosuppressive conditions and ,

Persons younger than 19 years of age who are receiving long-term aspirin therapy .

Treatment with antiviral drugs is recommended for all persons with suspected or confirmed influenza requiring hospitalization.

What are the treatment

recommendations?

Treatment, when indicated, should be initiated as early as possible (i.e., within 48 hours of illness onset) is more likely to be benefit .

Treatment should not wait for laboratory confirmation of influenza because laboratory testing can delay treatment and because a negative rapid test for influenza does not rule out influenza .

What is the antiviral dosage?

Oseltamivir

Treatment: 75-mg capsule twice per day for 5 days

Chemoprophylaxis: 75-mg capsule once per day for 10 days

Zanamivir

Treatment :10 mg (two 5-mg inhalations) twice daily for 5 days

Chemoprophylaxis :10 mg (two 5-mg inhalations) once daily for 10 days

What are the antiviral agents side

effects?

Oseltamivir

Nausea, vomiting( less severe if taken with food)

Transient neuropsychiatric event ) self injury, delirium) have

been reported in adults living in Japan

Zanamivir

Diarrhea, nausea, sinusitis, bronchitis, cough, headache,

dizziness

Each of these symptoms was reported by less than 5%

Is not recommended for patients with underlying airway disease

References:

World Health Organization (WHO)

Centre for disease control (CDC)

Control of communicable diseases manual

Infection control today