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Patient factors related to severity of H7N9
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The severity of influenza A(H7N9) appears to be more dependent on individual host factors, including age and comorbid conditions, compared with the severity of influenza A(H5N1) or influenza A(H1N1)pdm09, researchers from China reported in Clinical Infectious Diseases.
The researchers compared individual data from 123 patients with H7N9, 119 patients with H5N1 and 3,486 patients with pH1N1 to assess risk factors for hospitalization.
The median age of patients with H7N9 was 63 years, compared with 26 years for those with H5N1 and 25 for those with pH1N1. More patients with H7N9 were male compared with patients with H5N1 and pH1N1.
Patients with H7N9 had the highest prevalence of chronic medical conditions, including chronic heart disease and diabetes, and they also had a higher prevalence of smoking and hypertension. Chronic heart disease was associated with an increased risk of hospitalization among those with H7N9.
For H7N9 and H5N1, the signs and symptoms at hospital admission were similar, though patients with H7N9 were more likely to have fever, a productive cough and hemoptysis. Compared with patients with pH1N1, patients with H7N9 or H5N1 had elevated levels of alanine aminotransferase, creatinine kinase, C-reactive protein and lactate dehydrogenase. Leukopenia and thrombocytopenia were more common in patients with H7N9 or H5N1, compared with patients with pH1N1, but patients with H7N9 had more lymphopenia, and patients with H5N1 had more neutropenia.
Overall, 62% of patients with H7N9 required invasive ventilation, compared with 54% of those with H5N1 and 17% of those with pH1N1. The hospitalized case fatality rate was higher among those with H5N1. Death also occurred earlier for patients with H5N1, with a median time from illness onset to death of 11 days, compared with 15 days for pH1N1 and 18 days for H7N9. Lastly, patients with H7N9 were hospitalized for a longer duration.
“This comparative analysis shows that patients hospitalized with H7N9 virus infection share some risk factors with those hospitalized with pH1N1 infection, but have a clinical profile that more closely resembles H5N1 patients,” the researchers wrote in Clinical Infectious Diseases. “The identification in H7N9 patients of known risk factors for severe seasonal influenza and the more protracted clinical course compared to H5N1 patients suggests that host factors may be an important contributor to the severity of H7N9 virus infection.”
Disclosure: The researchers report no disclosures.
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