Influenza A (H1N1) Virus Infection in Hematologic patients In The South And West Of Spain

Patients with hematologic malignancies are likely to be at an increased risk for influenza infection. A few small series have documented seasonal influenza outbreaks among such patients, demonstrating the susceptibility of immunocompromised populations. These limited reports suggest that cancer patients are at a high risk for acquisition of influenza in both the community and health care settings. In April 2009, Mexico reported Influenza A virus outbreak. The virus was recognized as a novel known as Influenza A/pandemic 2009/H1N1 or 2009 H1N1 Influenza A. At present, there is scarce information on the clinical course of influenza A virus infection in hematologic patients.

To analyze the clinical course and laboratory characteristics of a cohort of hematologic patients diagnosed with influenza virus H1N1.

Prospective study in five centers in Andalucia and Extremadura (Spain), in hematologic patients who developed an influenza H1N1 virus infection in the winter of 2009. Clinical characteristics, laboratory, radiological findings and clinical course were collected and analyzed. Diagnosis of the infection was made by viral isolation determined by PCR in pharyngal or nasal samples or both. Patients were followed during at least one month after diagnosis of infection. Non-normal distribution data were expressed as median values (range). Chi-square test or Fisher exact test were used to compare differences between groups of categorical data. Differences were considered statistically significant for p-values <0.05. All statistical analyses were performed using SPSS 17.0 software (Chicago, IL).

A total of twenty-nine patients entered the study between September and December 2009. One patient had been vaccinated against influenza H1N1 virus. Fifty per cent were female, with a median age of 40 years (3-78). Hematolgic diseases were: acute leukemia (24.1%), multiple myeloma 13.8%, non-hodgkin lymphomas 17.2%, Hodgkin lymphoma 20.7%, chronic lymphocytic leukemia 10.3%, myelodysplastic syndrome 3.4%, hemoglobinopathies 6.9% and other hematologic diseases 3.4%. Twelve (41.4%) patients were hematopoietic stem cell recipients: allogeneic (58.3%), most of them from identical sibling (85.7%) and peripheral blood source (91.7%) and autologous (41.7%). Lymphopenia was observed in 72.4% cases and neutropenia in 27.6% cases. The median days between the initial symptoms and diagnosis was 2 days (0-7). Most patients were in an outpatient basis (82.2%) and only 8 patients (27.6%) were hospitalized for these reason. Thirteen patients (44.8%) presented radiologic findings: interstitial changes (54.5%) and alveolar condensation (45.5%). 28 patients received treatment with oseltamivir, most of them at 75 mg/12 h, during a median of 5 days (1-21) and 21 patients received simultaneously another antimicrobial therapy. Six patients (20.7%) needed mechanical ventilation. At the end of the follow up the global mortality was 20.7% (6 cases) being three death (10.3) caused by influenza A H1N1 virus infection. There was an increase risk of mortality in patients who had pneumonia at the beginning of the infection (9.5% vs 50%, p=0.033), suffered a respiratory co-infection (8% vs 60%, p=0.008), developed respiratory complications (0 vs 46.1%, p=0.005), progressed to pneumonia during the infection (4.7% vs 71.4%, p=0.001) or required mechanical ventilation (8% vs 66.7%, p=0.008). There were no differences in the evolution of HSCT recipients.

Respiratory co-infection, pneumonia at the beginning or during the infection and mechanical ventilation showed a relationship with fatal clinical course of influenza A/H1N1 virus infection in haematologic patients.

No relevant conflicts of interest to declare.