Day #316 - Swine Flu

Today we heard a case of a patient with undelying Wegner's Granulomatosis who presented with several days of fever and cough. Her chest xray showed no infiltrate. The majority of patients with influenza will present with cough (90%) and fever (~70%). Headache, myalgias, arthralgias, fatigue are also common but seen in only 50-60%. There is a rational clinical exam on influenza here.

The nasopharyngeal swab revealed influenza, which was PCR confirmed to be "swine flu"

Influenza evolves by two processes. Antigenic drift, where small mutations occur over time in the surface molecules which gradualy cause waning immunity. This is the basis of seasonal influenza.

Antigenic shift invoves abrupt changes in the surface molecules, often as a conseuqnce of recombination with swine or avian lineages, into a strain to which few in the population are likely to have immunity. This leads to epidemic (and pandemic) influenza.

Treatment of Influenza:

• Supportive care
• In patients admitted to hospital/ICU or those with severe disease or severe undelying co-morbidities should receive antiviral therapy (also give to healthy people with less than 72h of symptoms)
• Oseltamavir (neuraminadase inhibitor -- blocks entry of virus into cell) --> available orally, circulating H1N1 are resistant, circulating H3N2 are likely resistant.
• Zanamavir (neuraminadase inhibitor) --> inhalational only, all are currently succeptible
• Amandadine (M channel inhibitor) --> blocks release of viral RNA into the cytoplasm from the lysosome. Available orally, most H3N2 resistant, many H1N1 succeptible.

I have previously blogged about influenza here, here, and here.