Researchers find lessons in first NYC H1N1 deaths

May 3, 2010 (CIDRAP News) – In the early days of the H1N1 flu pandemic, a large outbreak at a New York City high school sent a strong signal of the virus's wide reach beyond southwestern states, and a review of the first several deaths in that city shows which patients were most at risk and how early antiviral treatment was vital.

The report, published in the Jun 1 issue of Clinical Infectious Diseases, details 47 confirmed fatal cases of pandemic H1N1 flu that were reported to the new York City Department of Health and Mental Hygiene and covers much of the city's first wave of infections from Apr 24 though Jul 1.

Early in the outbreak the city's health officials ordered enhanced surveillance and asked doctors to report all pandemic H1N1–related deaths, not just those in children. Medical examiners also collected postmortem samples on patients with suspected pandemic H1N1 infections, as well as those with a recent history of febrile respiratory illness who died outside of medical settings.

Illustrating the pattern that the new virus struck younger age-groups harder, unlike seasonal flu, the authors report that most of the patients who died were between ages 18 and 49; only 4% were age 65 or older. Nearly 80% had known risk factors for severe seasonal flu, and 58% were obese—a relatively new risk factor that emerged during the flu pandemic. (However, obesity was not significantly more common in those who died compared with those who survived their infections.)

The two most common underlying conditions were chronic pulmonary disease and diabetes, and 10 patients had asthma. Of 10 patients who didn't have an underlying medical condition, 8 were obese.

Fever was reported in all of the patients who died, and most had cough or shortness of breath. Vomiting and diarrhea were reported by 30% and 17% of patients, respectively.

Though bacterial coinfections generally haven't been a prominent feature in severe pandemic H1N1 infections, 13 of the 47 patients from New York City who died had an invasive bacterial coinfection, including Streptococcus pneumoniae (8) and Streptococcus pyogenes (3).

Of 28 patients who died more than 24 hours after hospital admission, all but 1 received mechanical ventilation. Nine more died in the emergency department, where they received emergency intubation. Of 31 patients who had medical review data, 14 had renal failure, of which 8 required dialysis.

For patients who sought medical care, the time between first clinical visit and hospitalization averaged about 3 days, with patients who had underlying conditions presenting earlier. When compared with patients who survived their infections, those who died presented about a day later.

Thirty-two (68%) of the 47 patients received oseltamivir (Tamiflu), with the median time from symptom onset to antiviral treatment averaging about 5.5 days. The pattern did not vary significantly between those with and without underlying conditions. Those who died were less likely to receive oseltamivir within 2 days of hospitalization compared with patients who survived.

The investigators wrote that the findings have important take-home messages for clinicians. They noted that some of the patients who died were not diagnosed with flu, despite having had contact with a healthcare system before they died, and 17 of the patients did not have fever upon initial presentation. The findings emphasize that community flu transmission, even when diagnostic tests are negative, shouldn’t discourage empirical treatment.

Also, the bacterial pneumonia findings underscore the importance of antibiotic treatment. "Because more than one-half of the invasive bacterial coinfections in this series were detected after death, empirical antibiotic treatment should be considered for patients with worsening influenza," the authors wrote, adding that their findings also highlight the ability of pneumococcal vaccine to reduce the number of severe flu infections and deaths.

Lee EH, Wu C, Lee EU, et al. Fatalities associated with 2009 H1N1 influenza A virus in New York City. Clin Infect Dis 2010 Jun 1;50(11):1498-504 [Abstract]

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