influenza (community medicine)
TRANSCRIPT
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!