Pandemic (H1N1) 2009 influenza

Abstract

The clinical picture in severe cases of pandemic (H1N1) 2009 influenza is markedly different from the disease pattern seen during epidemics of seasonal influenza, in that many of those affected were previously healthy young people. Current predictions estimate that, during a pandemic wave, 12-30% of the population will develop clinical influenza (compared with 5-15% for seasonal influenza) with 4% of those patients requiring hospital admissions and one in five requiring critical care. This review covers the background, clinical presentation, diagnosis, and treatment. The role of immunization and antiviral drugs is discussed. Experience from the first wave of pandemic (H1N1) 2009 influenza suggests that a number of infected patients become critically ill and require intensive care admission. These patients rapidly develop severe progressive respiratory failure which is often associated with failure of other organs, or marked worsening of underlying airways disease. The critical care management of these patients and the implications for resources is reviewed. Guidance from a range of bodies has been produced in a relatively short period of time in response to pandemic (H1N1) 2009 influenza. Disease severity has the potential to change, especially if there is virus mutation. Clinicians must be prepared for the unexpected and continue to share their experiences to maximize patient outcomes.

Different features of influenza A H1N1pdm09 virus infection among adults in 2009/10 and 2010/11

“…According to the results of the study conducted by Viasus et al, H1N1pmd09-positive patients hospitalized during the post-pandemic season were considerably older than those hospitalized during the pandemic season [16]. In our study, patients were more often treated with antiviral therapy in the pandemic season, and with antibiotics and antivirals in the post-pandemic season, which corresponds to the data reported previously [16,17]. Risk factors were more often registered in the pandemic season.…”

“…Compared to the pandemic season, during the post-pandemic season, patients were older by an average of seven years, indicating that the patient's age is an important risk factor for the severity of the disease, i.e., grounds for hospitalization during the postpandemic season. According to some European reports and our own study, patients with chronic pulmonary and cardiac diseases, obese people, and pregnant women form the highest-risk group for contracting the pandemic virus [4,17].…”

A retrospective evaluation of critically ill patients infected with H1N1 influenza A virus in Bursa, Turkey, during the 2009–2010 pandemic

“…The symptoms of H1N1 infection are similar to those of seasonal influenza (high temperature, cough, sore throat, runny nose, headache, and myalgia) 2,7,10,16,17,25 . In a study by Perez-Padilla et al 26 , the most frequently seen symptoms were reported to be fever, cough, and other respiratory problems.…”

Severe viral pneumonia in adults: what is important for the ICU physician?

“…Moreover, it is extremely complicate to predict the virulence owned by a specific viral strain and its interaction with the host's immune system. On one side, many families of respiratory viruses induce mild or very mild infection so they usually do not constitute a concern for intensive care unit (ICU) physician; on the other side, infection by specific viruses can lead to severe respiratory failure possibly because of an exaggerate inflammatory reaction, which is associated with severe pneumonitis and eventually acute respiratory distress syndrome (ARDS) [5,6]. This condition is usually associated with high mortality despite all treatment efforts, as was the case of pandemic H1N1/09 virus [5].…”

“…Usually, viruses associated with a high virulence spread as a breakthrough with high mortality rates; eventually, the severity of disease will decrease in the subsequent years. [5][6][7][8].…”