Influenza virus: Clinical manifestations, Complications, Diagnosis, Treatment and Prevention
Clinical manifestations
- H1N1
- causes swine flu is also known as swine influenza, hog flu, and pig flu.
- causes serious systemic manifestations
- Most infections are subclinical
- Fever, cough, rhinorrhea, fatigue, and headache.
- Vomiting in type B seen.
- There is no viremia
Complications
- Pneumonia:
- M.C. by str. pneumoniae
- Occurs most frequently in high-risk individuals with chronic pulmonary and cardiac disease and in elderly individuals
- Worsening of COPD
- Encephalitis
- Reye’s Syndrome:
- with type B virus
- GB. Syndrome
- GI Symptoms (gastric flu):
- With type B virus
Laboratory diagnosis
- Rapid viral tests:
- Detect viral nucleoprotein or neuraminidase
- Best specimen :
- Nasopharyngeal secretion
- Indirect fluorescent antibody
In India, facilities for isolation of influenza virus are available at the following institutes:
- Govt. of India, Influenza Centre, Pasture Institute, Coonor, South India
- Haffkine Institute, Mumbai
- School of Tropical Medicine, Kolkata
- All India Institute of Medical Sciences, New Delhi
- Vallabhai Patel Chest Institute, Delhi
- Armed Forces Medical College, Poona
H1NI influenza pandemic phases:
- Six Phases
- H1NI influenza pandemic is in phase 6
- A pandemic of H1N1 is suspected when :
- Cases are spread over 5 or more cities
- Swine Flu pandemic in 2009
Prevention
- Immunization.
- The vaccine is of following types.
a. Killed vaccine:
- Most commonly used vaccine:
- Contains H, N antigens
- Single dose
- No previous immune response 2 doses
- i.m
- Immunity lasts for only 3-6 months.
- Guillain-Bane syndrome (ascending paralysis) rarely seen.
b. Live attenuated vaccines:
- Administered as nose drops so induce both local and systemic immunity
c. New Vaccines
- Split virus vaccine (subvirion vaccine)
- Neuraminidase specific vaccine (sub-unit vaccine contains only N-antigen)
- Recombinant vaccine
Mild problems following inactivated flu vaccine:
- Soreness, redness, or swelling where the shot was given
- Hoarseness
- Sore, red or itchy eyes
- Cough
- Fever
- Aches
- Headache
- Itching
- Fatigue
- If these problems occur, they usually begin soon after the shot and last 1 or 2 days.
Moderate problems following inactivated flu vaccine:
- Young children-inactivated flu vaccine+ pneumococcal vaccine (PCV13) =increased risk for seizures caused by fever.
School Closure:
- School holidays reduced the reproduction number of Influenza H1N1 by 14-27% in different regions of India
- A significant impact of school holidays on the spread of pandemic influenza virus
Treatment
- Symptomatic
- with acetaminophen.
- But NSAID should be avoided in pt < 18 years of age due to risk of Reye’s syndrome.
- Maintain hydration and provide rest.
- Type A & B
- Specific antiviral Neuraminadase inhibitor oseltamivir and zanamivir
- The dosage of Oseltamivir for children
- 0 – 1 month of age 2 mg/kg BID x 5 days
- >1 month – 3 months 2.5 mg/kg BID x 5 days
- > 3 month – 1 year 3 mg/kg BID x 5 days
- Zanamivir is indicated in individuals > 5 year of age only
Type A
- Admantone agent amantadine and rimantidine .
Exam Question
Clinical manifestations
- H1N1
- causes swine flu is also known as swine influenza, hog flu, and pig flu.
- Swine Flu pandemic in 2009
- causes serious systemic manifestations
- Most infections are subclinical
- Fever, cough, rhinorrhea, fatigue, and headache.
- Vomiting in type B seen.
- There is no viremia
- A pandemic of H1N1 is suspected when :
- Cases are spread over 5 or more cities
Complications
Pneumonia:
- M.C. by str. pneumoniae
- Occurs most frequently in high-risk individuals with chronic pulmonary and cardiac disease and in elderly individuals
- Worsening of COPD
- Encephalitis
- Reye’s Syndrome:
- with type B virus
- GB. Syndrome
- G I Symptoms (gastric flu):
- With type B virus
In India, facilities for isolation of influenza virus are available at the following institutes:
- Govt. of India, Influenza Centre, Pasture Institute, Coonor, South India
- Haffkine Institute, Mumbai
- School of Tropical Medicine, Kolkata
- All India Institute of Medical Sciences, New Delhi
- Vallabhai Patel Chest Institute, Delhi
- Armed Forces Medical College, Poona
H1NI influenza pandemic phases:
- Six phases
- H1NI influenza pandemic is in phase 6
Prevention
a. Killed vaccine:
- Contains H, N antigens
- Guillain-Bane syndrome (ascending paralysis) rarely seen.
b. Live attenuated vaccines:
- Administered as nose drops so induce both local and systemic immunity
c. New Vaccines
- Split virus vaccine (subvirion vaccine)
- Neuraminidase specific vaccine (sub-unit vaccine contains only N-antigen)
Mild problems following inactivated flu vaccine:
- Soreness, redness, or swelling where the shot was given
- Hoarseness
- Sore, red or itchy eyes
- Cough
- Fever
- Aches
- Headache
- Itching
- Fatigue
School Closure:
- School holidays reduced the reproduction number of Influenza H1N1 by 14-27% in different regions of India
- Significant impact of school holidays on spread of pandemic influenza virus
Treatment
Type A & B
- Specific antiviral Neuraminadase inhibitor oseltamivir and zanamivir
- The dosage of Oseltamivir for children
- 0 – 1 month of age 2 mg/kg BID x 5 days
- >1 month – 3 months 2.5 mg/kg BID x 5 days
- > 3 month – 1 year 3 mg/kg BID x 5 days
- Zanamivir is indicated in individuals > 5 year of age only
Type A
- Admantone agent amantadine and rimantidine .
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