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Pneumonia, influenza A (H1N1) co-infection led to more severe disease, increased mortality
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Patients hospitalized for pneumonia who tested positive for influenza A (H1N1) during the spring outbreak in Mexico had more severe disease and higher death rates than those with pneumonia who tested negative for influenza.
Researchers retrospectively reviewed the medical charts as well as radiologic and lab findings of 98 patients hospitalized for acute respiratory illness at the National Institute of Respiratory Diseases in Mexico City. Eighteen patients had influenza-like illness accompanied by opacities on chest radiograph that indicated pneumonia and also had lab-confirmed influenza A (H1N1). The median age of patients was 38 years; eight had pre-existing conditions. The researchers compared the patients with coinfection to those with pneumonia who tested negative for influenza (n=21).
Among the influenza-positive group, seven patients died vs. three in the influenza-negative group (P=.06). Twelve patients in the influenza-positive group required invasive mechanical ventilation vs. four in the influenza-negative group (P=.053). Also, more patients in the influenza-positive group had renal failure upon admission.
None of the patients who tested positive for influenza were administered oseltamivir (Tamiflu, Roche) before admission. However, treatment with the drug was initiated for 11 patients upon admission and three between two and 10 days post-admission. Four patients who survived were not administered the drug, according to the researchers.
Risk factors for severe influenza A (H1N1) remain unknown. However, the researchers wrote that future studies “should identify predictive factors for severe disease and, especially, the effectiveness of early oseltamivir treatment and protection offered by having undergone seasonal influenza vaccination.” – by Meredith Ripa
Perez-Padilla R. N Engl J Med. 2009;361:680-689.
This report demonstrates that influenza virus infection is an important cause of morbidity and mortality, regardless of whether the infection is caused by the novel A/H1N1 or a seasonal strain of influenza. Although the numbers in this report are too small to permit reliable conclusions regarding the relative risk for complications from different influenza strains, this report reminds us that people with certain pre-existing medical conditions are at greater risk for hospitalization, have a greater need for mechanical ventilation and have more fatal outcomes than people who are not in a high-risk group. The second important message in this article is the observation that 22 health care workers developed nosocomial influenza infection after caring for patients with influenza, emphasizing the need for meticulous attention to respiratory precautions when a patient with influenza-like illness is admitted to the hospital.
– H. Cody Meissner, MD
Professor of Pediatrics, Tufts University School of Medicine, Boston