Is It Just “the Bug” or Is There a Missing Link?

The 2009 Pandemic Influenza A (H1N1) Virus Hospitalizations Investigation Team recently published its first report on the clinical characteristics of patients who were hospitalized with 2009 H1N1 influenza in the United States from April 2009 to mid-June 2009 ( Jain et al. N Engl J Med 2009; 361(20):1935. Epub 2009 Oct 8). It is the first comprehensive report and suggests the following two interesting points:

A high percentage of hospitalized patients with H1N1 (~73%), specifically children (60%), had at least one underlying medical condition predisposing them to severe illness. This is in comparison with 31% to 43% of children who were hospitalized with seasonal flu as mentioned in their report. This observation suggests that this novel virus is not any more virulent than the seasonal flu or may even be less virulent, so far, considering the fact that severe illness is more likely with seasonal flu infection than with H1N1 if the individual/child is otherwise healthy.

The other important point is that hospitalized patients with H1N1 have a much higher prevalence of obesity, particularly morbid obesity (defined by BMI equal to or greater than 40 in adults only), compared with the general population. It was reported that morbid obesity prevalence was five times greater in these hospitalized patients than in the general population.

We will learn more about this H1N1 pandemic as more reports are published. In the meantime, early initiation of antiviral therapy should be prompt, along with supportive care, as initiation of the antiviral treatment within 2 days of the onset of influenza-like illness was the only treatment significantly associated with a positive outcome among hospitalized patients in this study. It is, nevertheless, time to acknowledge the significance of obesity not only as it relates to our health-care system but also to the current H1N1 epidemic and to question ourselves: Is it just “the bug,” or is there a missing link?

Manish Joshi, MBBS, FCCP
Steering Committee Member