Influenza a (h1n1) virus infections in Hospitalised cancer patients: observation study at a regional cancer Institute in western India

Background: During initial months of 2015 an epidemic of novel Influenza A (H1N1) virus emerged in the western part of India especially in Ahmedabad, Gujarat and parts of Rajasthan. A similar surge in influenza cases were again noticed during the initial months of 2019. We are describing the clinical characteristics and mortality indicators of hospitalised cancer patients in our institute. Methods: We reviewed the case records retrospectively, of our patients who were hospitalized during the 2015 epidemic period and during the initial months of 2019. Patients with cancer and a microbiologically confirmed diagnosis of Seasonal Influenza A (H1N1) were evaluated. The demography, clinical parameters, laboratory reports and outcome data were collected, analyzed and presented here. A total of 24 and 22 hospitalized cancer patients, during 2015 and 2019 respectively, with confirmed H1N1 Influenza infection were studied. One patient was infected twice during the 2019 season. None of our patients were previously immunised with influenza vaccine. In the year 2015 out of the 24 patients 17(70.8%) were male and 7 (29.2%) were females, and that in 2019 12 (54.5%) were male and 10 (45.5%) were female. Haematological malignancies were present in 19 (79.2%) during 2015 epidemic, and in 19 (86.4%) patients in 2019. Number of patients with solid malignancies were 5 (20.8%) and 3 (13.6%) in 2015 and 2019 respectively. During both the episodes pneumonia was the most common manifestation in the hospitalized patients, bilateral being more common than a unilateral presentation. Oseltamavir was started within 48 hours of suspicion of influenza in 17 (58.3%) patients in the previous epidemic of 2015, and in 9 (39.2%) patients in the current year of 2019. Co-morbidities were present in 6(25%) and 6 (27.3%) patients in the two episodes respectively. Associated infections were present in 8 (33.33%) and 5 (21.7%) patients. Absolute lymphocyte count of less than or equal to 1000/microL was observed in 14 (58.3%) and 15 (65.2%) patients in 2015 and 2019 respectively. Altered biochemical parameters in the form of deranged LFT was found in 9 (37.5%) and altered RFT in 5 (20.8%) in the cohort of 2015, and the same were found in 5 (21.8%) and 4 (17.4%) patients observed during the 2019 study period. During the 2015 study, 13 (54.2%) and during 2019, 17 (74%) patients required intensive care. The overall hospital mortality in our cohort was 8 (33%) patients in 2015 and it increased to 15 (65.2%) patients in 2019. Adverse outcome in the patients was closely related to factors like presentation in the form of bilateral pneumonia, development of ARDS, time of commencement of oseltamavir (neuraminidase inhibitor), associated co-morbidities and infections, underlying malignancy and ongoing chemotherapy, absolute lymphocyte count of less than 1000 and multi organ failure. Presence of hypoxemia, bilateral pneumonia, and CURB 65 score more than equal to 3, timing of starting Neuraminidase inhibitors beyond 48 hours of presentation and lymphopenia were predictors of requirement of mechanical ventilation and death. Conclusion: Seasonal Influenza A infection in patients with cancer can cause severe illness, resulting in bilateral pneumonia, ARDS and death. Hypoxemia, bilateral pneumonia, CURB 65 score of more than equal to 3, timing of starting Neuraminidase inhibitors following symptoms, and lymphopenia were predictors of adverse outcome. Cancer patients are prone to develop more severe disease and require longer course of therapy with Neuraminidase inhibitors than the general population. Therefore, a larger study is needed to identify predictors for early suspicion and unfavourable evolution of influenza infection in these patients.