Influenza

Influenza / Bird flue / Swine flue

Definition : It is an acute highly infectious viral disease caused by influenza virus A, B and C. Characterised by high grade fever associated with malaise, headache, chills, sneezing, coryza etc.


AGENT FACTORS
Agent : Influenza virus A, B & C ( arthomyxoviridae family), antigenically different, no cross immunity. Type A & B viruses has antigen (Haemagulutinin and Neuraminidase)
Haemagulutinin (H antigen) - have 16 subtypes H1, H2, H3….H16It provide attachment of the virus to susceptible host.

Neuraiminidase ( N antigen) - have 9 subtypes N1, N2, N3….N9It is responsible for the release of the virus from the infected cells

Source Of Infection : Case - Clinical and Subclinical.
Infective Materials : Nasopharyngeal secretion.
Period Of Communicability : 1-2 days before & 1-2 days after the appearance of symptoms.


HOST FACTORS
Age : All ages are susceptible.
Sex : Equal effects on both sexes.
Mortality Rate : is high before 18 month and after 60 years of age.
Immunity : Develops after one week of infection and remains up to maximum 1 year.


ENVIRONMENTAL FACTORS
Season : Winter season is favorable.
Area : Increase attack rate in overcrowding area.

Incubation Period : 18-72 hrs.

Mode Of Transmission : Direct droplet & Droplet nuclei.



CLINICAL FEATURES
  1. Sudden onset of high grade fever with rigor and chills.
  2. Malaise, arthralgia and myalgia.
  3. Sneezing.
  4. Running nose.
  5. Lacrymation.
  6. Conjunctivitis.
  7. Cough.
In severe condition - 
  1. Respiratory rate increase
  2. Shortness of breath.
  3. Chest pain
  4. Dyspnoea (respiratory failure even death).

COMPLICATIONS
  1. Involvement of lower respiratory system.
  2. Pneumonia 
  3. Respiratory rate increased
  4. Chest in-drawing.
  5. Cyanosis.
  6. Respiratory failure
  7. Death.

PREVENTION & CONTROL
  1. Vaccination - Live attenuated vaccine (nasal spray), Killed vaccine, Split virus vaccine and Neuraminidase specific vaccine (duration of vaccine is maximum 6 month.
  2. Diagnosis - Isolation of virus from nasopharyngeal secretion by ELISA. Paired sera (check Ig level).
  3. Treatment - Neuraminidase inhibitors i.e. Oseltamivir (temiflue / flueviral ) 100 mg BD x 5 days and Zanamivir.

CLINICAL CATEGORIZATION OF FLUE PATIENT

Category -A
  1. Upper respiratory tract infection.
  2. Symptomatic treatment
Category - B
  1. Lower respiratory tract infection with expectoration
  2. Test to be done
  3. Antiviral to be given
  4. No need of administration
Category - C
  1. Respiratory failure
  2. Admit in ICU with ventilator and oxygen
  3. Dyspnoea
  4. Test to be done
  5. Antiviral to be given



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