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H1N1 (Swine Flu): Two New Studies Reveal Impact of H1N1 On Patients and Hospitals – More Serious In the Young

October 10, 2009

Two very interesting and revealing studies have been released in the online version of the New England Journal of Medicine.

  • One study discusses the impact to Intensive Care Units (ICU)  in the southern hemisphere (Australia and New Zealand) and their experience with the H1N1 virus.
  • The second reviews the impact to patients and health care systems in the first wave (Spring 2009) in the United States.  The US study confirmed that the H1N1 is a more serious illness in young people and often presents with different symptoms than seasonal flu – for example, 40 percent of the patients had diarrhea and vomiting, a rare occurrence in seasonal flu.

The net-net of both of these studies is that although most of the H1N1 disease is mild, for some it is life-threatening (especially young people) and the illness can negatively impact patient outcomes and health care systems.

CRITICAL CARE SERVICES AND 2009 H1N1 INFLUENZA IN AUSTRALIA AND NEW ZEALAND

The premise of the study was that planning for the treatment of infection with the 2009 pandemic influenza A (H1N1) virus through health care systems in developed countries during winter in the Northern Hemisphere was hampered by a lack of information from similar health care systems.

The researchers conducted an inception-cohort study in all Australian and New Zealand intensive care units (ICUs) during the winter of 2009 in the Southern Hemisphere.

The researchers conducted an inception-cohort study in all Australian and New Zealand intensive care units (ICUs) during the winter of 2009 in the Southern Hemisphere.

They calculated, per million inhabitants, the numbers of ICU admissions, bed-days, and days of mechanical ventilation due to infection with the 2009 H1N1 virus. They also collected data on demographic and clinical characteristics of the patients and on treatments and outcomes.

What they discovered was from June 1 through August 31, 2009, a total of 722 patients with confirmed infection with the 2009 H1N1 virus (28.7 cases per million inhabitants).

  • 95% confidence interval [CI], 26.5 to 30.8) were admitted to an ICU in Australia or New Zealand (of the 722 patients)
  • 669 (92.7%) were under 65 years of age and 66 (9.1%) were pregnant women (of the 601 adults for whom data were available)
  • 172 (28.6%) had a body-mass index (the weight in kilograms divided by the square of the height in meters) greater than 35
  • Patients infected with the 2009 H1N1 virus were in the ICU for a total of 8815 bed-days (350 per million inhabitants)
  • The median duration of treatment in the ICU was 7.0 days (interquartile range, 2.7 to 13.4)
  • 456 of 706 patients (64.6%) with available data underwent mechanical ventilation for a median of 8 days (interquartile range, 4 to 16)
  • The maximum daily occupancy of the ICU was 7.4 beds (95% CI, 6.3 to 8.5) per million inhabitants
  • As of September 7, 2009, a total of 103 of the 722 patients (14.3%; 95% CI, 11.7 to 16.9) had died, and 114 (15.8%) remained in the hospital

Their conclusions? The 2009 H1N1 virus had a substantial effect on ICUs during the winter in Australia and New Zealand.

Their conclusions? The 2009 H1N1 virus had a substantial effect in Intensive Care Units during the winter in Australia and New Zealand.

http://content.nejm.org/cgi/content/full/NEJMoa0908481?query=TOC

Hospitalized Patients with 2009 H1N1 Influenza in the United States, April–June 2009

This study describes the clinical characteristics of the patients who were hospitalized with 2009 H1N1 influenza in the United States from April 2009 to mid-June 2009.

This study describes the clinical characteristics of the patients who were hospitalized with 2009 H1N1 influenza in the United States from April 2009 to mid-June 2009.

Using medical charts, researchers collected data on 272 patients who were hospitalized for at least 24 hours for influenza-like illness and who tested positive for the 2009 H1N1 virus with the use of a real-time reverse-transcriptase–polymerase-chain-reaction assay. Of the 272 patients studied, here is what they found:

  • 25% were admitted to an intensive care unit
  • 7% died
  • Forty-five percent of the patients were children under the age of 18 years
  • 5% were 65 years of age or older
  • Seventy-three percent of the patients had at least one underlying medical condition; these conditions included asthma; diabetes; heart, lung, and neurologic diseases; and pregnancy
  • Of the 249 patients who underwent chest radiography on admission, 100 (40%) had findings consistent with pneumonia
  • 42 percent had diarrhea and vomiting — usually rare with seasonal flu
  • All the patients had fever and cough
  • Of the 268 patients for whom data were available regarding the use of antiviral drugs, such therapy was initiated in 200 patients (75%) at a median of 3 days after the onset of illness
  • Data suggest that the use of antiviral drugs was beneficial in hospitalized patients, especially when such therapy was initiated early

The study derived four conclusions:

  1. 2009 H1N1 influenza caused severe illness requiring hospitalization, including pneumonia and death.
  2. Nearly three quarters of the patients had one or more underlying medical conditions.
  3. Few severe illnesses were reported among persons 65 years of age or older.
  4. Patients seemed to benefit from antiviral therapy.

http://content.nejm.org/cgi/content/full/NEJMoa0906695?query=TOC

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