Influenza virus: Clinical manifestations, Complications, Diagnosis, Treatment and Preventio

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:

  1. Govt. of India, Influenza Centre, Pasture Institute, Coonor, South India
  2. Haffkine Institute, Mumbai
  3. School of Tropical Medicine, Kolkata
  4. All India Institute of Medical Sciences, New Delhi
  5.  Vallabhai Patel Chest Institute, Delhi
  6. 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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