CDC finds patterns in novel flu hospitalizations

May 19, 2009 (CIDRAP News) – In a first early look at trends in patients who have been hospitalized with novel influenza H1N1infections, the Centers for Disease Control and Prevention (CDC) said today that all but one of a group of 30 patients presented with fever and that about two thirds of them had an underlying medical condition.

The CDC's review, based on California patients who were hospitalized from Apr 20 through May 17, appeared yesterday in an early online version of Morbidity and Mortality Weekly Report (MMWR). Anne Schuchat, MD, interim deputy director CDC's science and public health program, said during a media briefing today that the majority of patients recovered without problems after short hospitalizations, though some had severe illness with prolonged complications and remain hospitalized.

As of May 17, California officials have reported 553 confirmed or probable novel influenza cases. The 30 patients who were hospitalized are from 11 counties, most located in the southern or central part of the state. The age range was 27 days to 89 years, with a median age of 27.5 years.

The report contains detailed clinical descriptions of four patients that represent a range of illness severity, including:

  • A 5-month-old girl who was born premature, has multiple underlying health conditions, and apparently became infected with the new flu strain at the hospital, where she remains
  • A 29-year-old woman, previously healthy, who had pneumonia, was treated in the intensive care unit (ICU), and was discharged from the hospital after 9 days
  • A 32-year-old man with a history of obstructive sleep apnea who had pneumonia, was treated in the ICU, and was discharged from the hospital after 10 days
  • An 87-year-old woman with multiple health conditions who remains hospitalized in critical condition

The most common diagnoses at admission were pneumonia and dehydration. Of the 19 patients who had underlying health conditions, the most common were chronic lung disease, immunosuppression, cardiac disease, diabetes, and obesity. The most common symptoms were fever, cough, vomiting, and shortness of breath. "That's unusual for seasonal flu," Schuchat said.

Five of the patients were pregnant. Two of the women miscarried—one at 13 weeks and the other at 35 weeks. CDC officials emphasized last week that pregnancy is a known influenza risk factor and that pregnant women who have suspected, probable, or confirmed novel flu cases should receive oseltamivir (Tamiflu) for 5 days.

None of the patients had microbiological evidence of a secondary bacterial infection. Schuchat said that mirrors what CDC officials are seeing elsewhere, but she added that researchers are monitoring the situation closely. A previous report on Mexican patients who died from novel influenza infections also indicated that many had viral, not bacterial, pneumonia.

Half of the patients received oseltamivir, and five were treated within 48 hours of symptom onset. Of the 15 who didn't receive antiviral treatment, 6 sought medical care more than 48 hours after they got sick.

Though the patients who needed prolonged intensive care were more likely to be very young, be very old, or have a debilitating underlying medical condition, the CDC emphasized that one 18-year-old patient who was relatively healthy and had only mild chronic lung condition required ICU treatment and a ventilator.

Schuchat said the CDC recommends that all hospitalized patients be monitored carefully and receive antiviral therapy, even if they're past 48 hours of symptom onset.

CDC. Hospitalized patients with novel influenza A (H1N1)virus infection, California, April-May 2009. MMWR 2009 May 18;58(Early Release):1-5 [Full text]

See also:

May 12 CIDRAP News story "CDC urges vigilance for pregnant women with flu symptoms"

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