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H1N1 in Adults Can Be Severe

In California, mortality was higher among hospitalized adults than among hospitalized children.

Most epidemiologic data on this year's cases of H1N1 influenza indicate that infection risk is highest in infants, children, and adolescents. However, adults should not underestimate their risk from this infection; in severe cases, risk for flu-related death is relatively high, according to a new report.

Between April and August 2009, 1088 Californians (median age, 27) developed severe PCR-confirmed H1N1 influenza that led to hospital admission, death, or both. Population-based case rates were highest for infants (age, <1 year; 11.9 per 100,000) and lowest for older adults (age, 70; 1.5 per 100,000). However, case fatality rates were considerably lower for hospitalized infants, children, and teenagers than for older patients: Of 118 deaths, 110 occurred among the 744 adults in the study.

The authors report the following data for hospitalized adults:

• 80% were admitted to intensive care units, and 93% required mechanical ventilation.
  
• 97% had radiologically confirmed pneumonia, although secondary bacterial infection was remarkably uncommon in all age groups (38/744 adults and 8/344 children).
  
• Almost 75% had underlying medical conditions (e.g., diabetes, chronic lung disease, immunosuppression) known to worsen influenza outcomes.
  
• Of those with known body-mass indexes, more than half were obese, and 25% were morbidly obese (vs. a national rate of morbid obesity of 4.8%).
  

Comment: Although adults seem to be relatively protected against H1N1 infection, they can still acquire life-threatening infections. However — as with most H1N1 data right now — we have no true denominator of infection in this study, so these sobering observations await clarification with additional data on baseline infection rates in adult populations.

— Abigail Zuger, MD

Published in Journal Watch General Medicine November 19, 2009

Citation(s):

Louie JK et al. Factors associated with death or hospitalization due to pandemic 2009 influenza A(H1N1) infection in California. JAMA 2009 Nov 4; 302:1896.

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• Late death secuela BOOP
  arturo flores, HOSPITAL BETANIA, 1 Dec 2009 1:01 PM EST
  Death about Oganized Pneumonia is common in patients that survived of H1N1 one month afther primo-infection.

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