Dr Muhammad Athar Khan MBBS,DPH,DCPS-HCSM(MPH),MBA MCPS,PGD-Statistics,DCPS-HPE Associate Professor Department of Community Medicine Liaquat College of Medicine & Dentistry

1. DR ATHAR KHAN - LIAQUAT COLLEGE OF MEDICINE & DENTISTRY
INFLUENZA
DR ATHAR KHAN
LIAQUAT COLLEGE OF MEDICINE & DENTISTRY
Causative agent:
Orthomyxovirus, 3 types: A, B, C
– Type A: outbreaks/ epidemics; Only cause of pandemics
– Type B
– Type C: Not circulating currently
Currently circulating influenza viruses in world:
– H1N1 (Type A) – Cause of Swineflu
– H2N2 (Type A)
– H5N1 (Type A) – Cause of Avian influenza (Birdflu)
– H3N2
– H7N9
– Type B
Cyclical trends in Influenza:
– Type A epidemics every 2 – 3 years
– Type B epidemics every 4 – 7 years
– Type A pandemics every 10 – 15 years
Antigenic variations in Influenza:
(Type A)

2. DR ATHAR KHAN - LIAQUAT COLLEGE OF MEDICINE & DENTISTRY
Antigenic shift: Occurs due to Genetic recombination/ reassortment/rearrangement,
Nature Sudden, May lead to Epidemics/ Pandemics
Antigenic drift: Point mutation, Gradual/ insidious, Sporadic cases
Incubation period:
18 – 72 hours
Period of infectivity:
1 – 2 days before to 1 – 2 days after onset of symptoms
AVIAN INFLUENZA
• Also known as ‘Bird flu’ or ‘Highly pathogenic avian influenza’
• Causative agent: H5N1 (Type A Influenza virus)
• Avian Influenza is a Pandemic: Origin from Hong Kong (1997)
• Drug of choice: Oseltamivir (Tamiflu) 75 mg BD × 5 days (contraindicated in infants)
Influenza: Pandemic (H1N1) Influenza 2009 [NEW NOMENCLATURE: Influenza A
(H1N1) pdm 09]
• WHO declaration of Influenza pandemic: 11 June 2009
– World is now post-pandemic EXCEPT: INDIA and NEW ZEALAND (locally intense
transmission)
• Incubation period: 2–3 days
• Clinical features:
– Uncomplicated influenza: Influenza like illness (Fever, cough, sorethroat, rhinorrhoea,
headache, muscle pain), GIT illness (diarrhoea WITHOUT dehydration)
– Complicated/severe influenza: Pneumonia, CNS involvement, Severe diarrhoea,
Secondary complications,
– Exacerbation of chronic diseases

3. DR ATHAR KHAN - LIAQUAT COLLEGE OF MEDICINE & DENTISTRY
– Progressive disease: Oxygen impairment/cardiopulmonary insufficiency, CNS
complications, Invasive secondary bacterial infection, Severe dehydration
• Risk factors of severe disease:
– Infants and children < 2 years
– Pregnant females
– COPD
– Chronic cardiac disease
– Metabolic disorders
– Chronic renal/hepatic/neurological/hemoglobinopathies/immunosuppression
(INCLUDING HIV) disorders
– Children on aspirin therapy
– Persons aged > 65 years
– Morbid obesity
• Laboratory diagnosis:
– Most timely and sensitive detection: RT-PCR test
– Samples: Nasopharyngeal + throat swabs [Tracheal/bronchial aspirates in lower
respiratory tract infection cases]Q
– Point-of-care/Rapid diagnostic tests: Not recommended
• Duration of isolation: for 7 days after onset of illness OR 24 hours after resolution of
fever/respiratory symptoms whichever is longer
• Antiviral therapy:
– Severe/progressive clinical illness: OseltamivirQ (if not available or resistance, use
Zanamivir)
– High risk of severe/complicated illness: Oseltamivir OR Zanamivir
– Not high risk OR Uncomplicated confirmed/suspected illness: No need of treatment

4. DR ATHAR KHAN - LIAQUAT COLLEGE OF MEDICINE & DENTISTRY
Avian Influenza H7N9
• Origin: China 2013
• Spread to: Hong Kong
• Disease burden:
– Case fatality rates: 33%
• MC age group affected: Older males (>50 years age)
• Mode of transmission: Respiratory (Live bird markets)
– Human to human transmission: Rare but possible
• Treatment: Neuraminidase inhibitors
– Oseltamivir
– Zanamivir
Vaccines for Influenza
• Killed vaccines:
– 2 doses, 3 – 4 weeks apart, 0.5 ml (for age > 3 years), subcutaneous
– 70 – 90% protective efficacy; duration 3 – 6 months
– Is rarely associated with Guillain Barre SyndromeQ (GBS)
• Live attenuated vaccines:
– Stimulate local + systemic immunity
– Antigenic variations presents difficulties in manufacture
• Newer vaccines:
– Split – virus vaccine:
- Also known as ‘Sub-virion vaccine’
- Highly purified

5. DR ATHAR KHAN - LIAQUAT COLLEGE OF MEDICINE & DENTISTRY
- Lesser side effects
- Less antigenic – multiple injections required
- Useful for children
– Neuraminidase – specific vaccine:
- Sub-unit vaccine containing N-antigen
- Permits subclinical infection – long lasting immunity
– Recombinant vaccine:
- Antigenic properties of virulent strain transferred to a less virulent strain
– Contraindications to Inactivated Influenza vaccines:
- Severe allergy to chicken eggs
- History of hypersensitivity/anaphylactic reactions previously
- Development of Guillain Barre Syndrome (GBS) within 6 weeks of vaccine
- Infants less than 6 months age
- Moderate-to-severe illness with fever
H1N1 (Swine flu) Vaccine
• H1N1 Inactivated vaccine: Single i/m injection
– Strain: A/California/7/2009 (H1N1) V like strain
– Storage temperature: +2° to +8° C
– Contraindications: History of anaphylaxis/severe reaction/Guillian Barre Syndrome,
Infants < 6 months, Moderate-to severe illness with fever
– Protective immunity: Develops after 14 days (NOT 100%)
• H1N1 Live attenuated vaccine: Nasal spray
– Side effects: Rhinorrhoea, nasal congestion, cough, sore throat, fever, wheezing,
vomiting

6. DR ATHAR KHAN - LIAQUAT COLLEGE OF MEDICINE & DENTISTRY
• Priority groups (in order) for Influenza vaccines:
– Pregnant women
– Age > 6 months with chronic medical conditions
– 15-49 years healthy young adults
– Healthy young children
– Healthy adults 49-65 years
– Healthy adults >65 years