INFLUENZA

Also know as ‘’SEASONAL FLU’’

• Influenza is an ‘acute Respiratory tract infection’ caused by influenza virus characterized by sudden onset of chills, malaise, fever, muscular pain and cough.

CAUATIVE AGENT

• ‘’INFLUENZA VIRUS’’ 3 types - Type A

- Type B - Type Cpandemic were caused by ‘’TYPE A’’

PROBLEM STATEMENT

• Its an international disease • Occur in all countries and affect millions of people • May occur pandemic every 10-40 years due to major antigenic changes as

occurred in

- 1918 … SPANISH INFLUENZA -1957… ASIAN INFLUENZA -1968….. HONG KONG INFLUENZA

AT PRESENT

• A(H1NI)• A(H3N2)• INFLUENZA B

• WHO identify human infection with a new strain A(H5NI) In HONG KONG in mid 1997

EPIDEMIOLOGICAL DETERMINANTS

AGENT FACTOR

AGENT FACTOR

• Influenza virus are classified under ‘’ORTOMYXOVIRS’’• Out of A,B and C types A and B are responsible for epidemics throughout the

world • Influenza A virus have 2 distinct surface antigen

- Heamagglutinin (H)…. Attachment of virus to susceptible cell - Neuraminidase (N)….. Release of virus from infected cell

• No antigenic shifts of type B virus

What is antigenic shift and drift

• Antigenic shift results from genetic recombination of human and animal or avian virus

• Antigenic Drift involve point mutation in the gene • Type B show lessor degree changes and Type C is antigenically stable

ANTIGENIC CHANGES

ANTIGENIC SHIFT ANTIGENIC DRIFT

RESERVOIR OF INFECTION

• Major reservoir of influenza are animals and birds • Virus isolate from many animals and birds like swine,

horses , dogs, domestic poultry, and wild birds etc. New stains form due to recombination between man, animals and birds.

SOURCE OF INFECTION

• Cases or subclinical cases • During epidemic asymptomatic infection occur,

play important role in spread of infection • Respiratory tract secretions are also infective

Period of infectivity

• Virus is present in nasopharynx from 1-2 DAY BEFORE AND 1-2 DAY After onset of symptoms

HOST FACTOR

AGE and SEX

• All age groups and both sexes are affected• Attack rate is lower among adults • Children constitute an important link in

transmission chain

Mortality rate

• Highest mortality rate during epidemic among

- Old People (generally over 85) - Children under 18 months - Or person with systemic diseases such as: - chronic heart disease CHD - respiratory diseases - renal disease - also seen among diabetics person

IMMUNITY

• Specific antibodies against HA and NA • Resistance to initiation of infection is related to antibody against

HA • Decrease severity of disease and decrease transmission related to

NA

ENVIONMENTAL FACTIOR

• SEASON

- Epidemic usually occur in winter month in northern hemisphere - In southern hemisphere outbreaks occur in winter or rainy season • OVERCROWDING - Enhance transmission

MODE OF TRANSMISSION

• Person to person by droplet infection or droplet nuclei• Use of fomites

• PORTAL OF ENTERY is respiratory tract

INCUBATION PERIOD

18-72 hours

PATHOGENSIS

Virus

Superficial EPI of respiratory tract

Inflammation

Necrosis

CLINICAL FEATURES

• Fever • Chills• Generalized ache and pain• Headache and myalgia • Coughing • Generalized weakness - Fever last for 1-5 days and average 3 days in adults

COMPLICATIONS

• Sinusitis • Otitis media• Purulent bronchitis• Pneumonia• Ray syndrome

(type B)

PANDEMIC INFLUENZA

• H1NI 2009 • Diff in pathogenesis from seasonal influenza in aspects • Little or no pre-existing immunity against virus wider impact of infection

among children and young adults • Virus can infect the Lower respiratory tract infection

rapidly progress to pneumonia especially in children and young to middle age group

• Incubation period approx. 2-3 DAYS up to 7 days

CLINICAL FEATURES

Uncomplicated influenza • Fever• Cough• Sore throat • Muscle pain• Malaise• No dyspnea and shortness of breath • GIT symptom may also present

Complicated influenza • Shortness of breath and dyspnea • Lower RTI ( pneumonia )• CNS involvement• Sever dehydration• Secondary complications• COPD asthma renal failure

RISK FACTORS

• Infant and young children under 2 year of age • Pregnant females • Person of COPD or asthma • Chronic cardiac disease • Metabolic disorder, like diabetes• Chronic renal failure • Hepatic failure • Immunocompromised patient• Aspirin therapy• Old age

LAB DIAGNOSIS

• VIRUS ISOLATION - virus can be detected by indirect fluorescent antibody technique

• SERIOLOGY - Heamagglutination inhibition (HI) and ELISA • 4 folds r greater increase in titer indicate the influenza infection

PREVENTION

• Good ventilation of public buildings • Avoid overcrowding specially during epidemics • Cover your mouth while sneezing and coughing • Immunization vaccine must administrate at least 2 weeks before the onset of epidemic• Due to antigenic changes new vaccinations are always required

VACCINE FOR SELECTED POPULATION

• In industries to reduce absenteeism • In public servants to prevent critical public services • Certain age groups like elders and children under 18 month to

prevent from sever complications • Also the people with chronic illness like systemic diseased to

prevent death

Killed vaccine

• Required strains of vaccine are grown in allantonic cavity of chick embryo

• Harvested purified and killed by beta- propiolacton • Formulation: aqueous or saline • Administration: - 0.5ml for adults and children over 3 years - 0.25ml for children from 6 to 36 month of age (3 years )

ROUT

• Site of injection - Intramuscular - Subcutaneous

LIVE ATTANUATED VACCINE

• A trivalent live attenuated vaccine administered as a single dose intranasal spray

• For healthy individual avoid in Immunocompromised patient

CONTRAINDICATION OF VACCINE

• People with h/o anaphylactic shock • People with h/o sever reaction to influenza vaccine • Who develop Guillain-Barre syndrome • Children less then 6 month of age (inactivated influenza vaccine is not

approved)• People with moderate to sever fever

DRUG TREATMENT

• Symptomatic treatment • Prophylaxis - Neuraminidase inhibiters - Zanamivir and oseltamivir• Influenza A is treated with zanamivir or combination of oseltamivir

and rimantadine • Influenza B is treated with osaltamivir

Factors contribute to rapid spread

• Short incubation period • Large number of subclinical cases• High proportion of susceptible population • Short duration of immunity • Absence of cross immunity

AVAIN INFLUENZA H5NI

• Also called Bird Flu…Primarily infect birds • H5N1 strain first infect humans in Hong Kong causes 18

cases and 6 deaths• Poultry Outbreak in Pakistan in 2006• Worldwide spread of disease since 2007

THANK YOU FOR YOUR ATTENTION!