Influenza

Background

1. 3 types, 2 of which cause dz in humans
   1. type A- most common and causes world pandemics- also found in pigs, horses, seals, whales and birds
   2. type B- only found in humans- causes regional epidemics, not global
   3. type C- no human dz

Epidemiology

1. transmitted by resp secretions or hand to hand. Infection limited to resp epithelium and ciliated columnar cells involved initially. Viremia rare.
2. symptoms start within 18 hrs, pt contagious for 2- 5 days. Usually involve sudden onset fever, malaise, headache. Later get sore throat, myalgia, cough and sputum. Cough can last for 2 wks. Can have vomiting and diarrhea in kids or even present as croup, bronchiolitis or febrile seizures.

Treatment

1. generally supportive but can use antivirals
   1. Amantadine- reduces fever and symptoms by 1- 2d. Targets M2 membrane protein of influ A. Has neurologic side effects (lightheadedness, nervous, confusion, insomnia) and resistance developing and not useful against Type B.
   2. Flumadine- like amantadine but fewer side effects. Not for kids
   3. Neuraminidase Inhibitors- Relenza and Tamiflu. Inhibition of neuraminidase activity prevents spread and aborts infection. Works with all strains. Limited resistance.
   4. Relenza- decreases symptoms by 1.5- 2.5 days. Use if age 7 or older and within 48 hrs of sxs.
   5. Tamiflu- reduces duration of dz by 1.5 days but better yet, reduces by 50% sequela like otitis media, sinusitis, bronchitis, pneumonia

Complications

1. post influenza asthenia- elderly can have malaise and lassitude requiring prolonged convelescence.
2. viral pneumonia-
3. secondary bacterial pneumonia- seen during recovery phase- staph, strep, hemophilus
4. myositis- calf muscle pain with elevated CPK seen in kids with influ B
5. Reyes Syndrome- fatty liver degeneration seen in viral syndrome tx?ed with ASA. Get liver failure, hepatic encephalopathy and brain edema
6. can also see encephalitis, Guillain Barre, transverse myelitis, myocarditis, pericarditis

Source

6/06 MISTRY