Pregnancy, obesity and other risk factors for complications in influenza A(H1N1) pdm09 infection

Although influenza is usually a self-limited disease, patients who develop complications are at increased risk of hospitalization, intensive care unit admission and death. Since preventive and early therapeutic measures should be prioritized in higher risk patients, identification of the risk factors for severe infection is important from a public health perspective. Risk factors for complications in pandemics may show some differences with regard to seasonal influenza. During the influenza A(H1N1)pmd09 pandemic, although many cases occurred in younger adults, the risk factors identified for severe infections and complications were similar to those for seasonal influenza, including chronic respiratory, renal, liver, and heart diseases. Aged patients, although less frequently affected, were also at higher risk. Obesity, and particularly morbid obesity (>40 body mass index) has been noted as a significant risk factor for severe disease in the 2009 influenza pandemic. Some interesting recent studies provide insights into the biological reasons behind the poor outcomes in morbidly obese patients. In terms of pregnancy, the studies have shown contradictory results due to variations in methodology and medical care. However, it seems that pregnancy, particularly during the third trimester, increases the risk of complications, and that early antiviral treatment is associated with improved outcomes.