| ID | 85 |
|---|---|
| Name | INFLUENZA |
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| Introduction | Influenza is also a viral infection and mainly caused by a group of myxoviruses. It is a highly contagious disease, transmitted by the respiratory route primarily by droplet nuclei. It occurs usually epidemically in the fall or winter and also sporadically in the summer. The influenza viral infection has an incubation period of 1-4 days. Common types of influenza viruses are- A, B and C, where type A strain can infect a variety of mammals (humans, swine, horses, etc), and birds, type B and C infect almost exclusively humans. The infections caused by type A and B are clinically indistinguishable but type C produces a minor illenss. Now a day, the main circulating influenza viruses are the human-origin A (H1N1) and (H3N2) subtypes, and also type B. |
| History | |
| Etiology | |
| Clinical Features | Clinical features: 1. Sudden onset of malaise, headache. 2. Generalised aches and pain. 3. Anorexia, sometimes nausea, vomiting. 4. Fever upto 104°F with chill & shivering, occasionally rigor. Palate, tonsil, conjunctiva may be congested. 5. Face is flushed & fauces are hyperaemic. 6. Cough may be unproductive with harshness. 7. Complications may be- bronchitis, tracheitis, bronchiolitis, bronchopneumonia, post influenzal asthenia and depression etc. • Danger- toxic cardiomyopathy when pre-existing cardiac disease. |
| Preventions | Prevention: 1. Vaccination: Trivalent influenza virus vaccine 0.5ml i.m once annually-provides partial immunity (about 85% efficacy) for a few months to 1 year. The vaccine is contraindicated in persons with hypersensitivity to chicken eggs or other components of the vaccine, persons with an acute febrile illness, or thrombocytopenia. 2. Chemoprophylaxis in epidemics: i. Chemoprophylaxis against influenza A and B can be done with the neuraminidase inhibitors- oseltamivir 75mg daily orally and zanamivir 10mg daily by inhalation, but resistance to the former is increasingly prevalent in human-origin A (H1N1) strain, ii. Amantadine hydrochloride (or rimantadine, preferred in patients with renal failure) 200mg/day (or 100mg/day in elderly as they develop CNS side effects) orally in two divided doses for 10 days, will markedly reduce the attack rate among exposed individuals if begun immediately. |
| Treatment | Treatment: General & symptomatic treatment: 1. Complete rest in bed. 2. Analgesics: Acetaminophen rather than aspirin should be used for fever, especially in children. 3. If nasal congestion- nasal decongestants e.g ephedrine (1%) or oxymetazoline or xylometazoline drop or spray may be applied locally for short period. 4. Antihistamine preparations- help to reduce irritation, sneezing & secretion. 5. If sore throat, warm saline gurgling, steam inhalation are useful. 6. Cough suppressant: Pholcodine 5-10mg 6-8 hourly; or any cough suppressant, according to the choice of the physician. 7. Treatment of bacterial complication (if any)- by appropriate antibiotic. 8. Treatment of other complications (if any) should be given. Antiviral therapy: Antiviral therapy may be effective and beneficial if it can be started at the earliest time (before 48 hours of attack) against the susceptible strains of influenza viruses. The expected benefits are reduction in the duration of signs & symptoms as well as secondary complications such as otitis, sinusitis, or pneumonia etc. 1. Antiviral chemotherapy against influenza A and B can be done with the neuraminidase inhibitors- i. oseltamivir 75mg twice daily orally for 5 days; or, ii. zanamivir 5mg inhalation twice daily for 5 days. 2. Amantadine hydrochloride (or rimantadine, preferred in patients with renal failure) 200mg/day (or 100mg/day in elderly) orally in two divided doses for 10 days, can be used for treatment with neuraminidase inhibitors only when human origin influenza A (H1N1) is the dominant viral strain, because these are inactive against influenza A (H3N2) and influenza B viruses. |
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