When the immune system Can't fight back: tracking three respiratory viruses

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Presence of severe immunosuppression, defined as any of the following: * active leukemia or lymphoma; * disseminated malignancy; * aplastic anemia; * graft-versus-host disease (GVHD); * congenital immunodeficiencies (e.g., common variable immunodeficiency); * treatment with immune checkpoint inhibitors or recent radiotherapy; * solid organ transplantation with immunosuppressive therapy; * immunosuppressive drugs related to transplantation (cyclosporine, tacrolimus, sirolimus, everolimus, azathioprine, mycophenolate mofetil); * hematopoietic stem cell transplant (HSCT) within two years or ongoing immunosuppressive therapy; * high-dose systemic corticosteroids (≥20 mg of prednisone/day or equivalent for ≥2 weeks); * alkylating agents (e.g., cyclophosphamide) or antimetabolites such as methotrexate (\>0.4 mg/kg/week), azathioprine (≥3 mg/kg/day), or 6-mercaptopurine (≥1.5 mg/kg/day); * chemotherapy agents for cancer; * TNF-alpha inhibitors (etanercept, adalimumab, certolizumab, golimumab, infliximab); * biologics or lymphocyte-depleting agents (e.g., thymoglobulin, alemtuzumab); B-cell depleting agents (e.g., rituximab); * HIV-positive patients with CD4 count \<200 cells/mm³, AIDS diagnosis, or symptomatic HIV. * Suspected acute viral respiratory infection, defined per European Conference on Infections in Leukemia (ECIL) criteria as meeting all of the following: clinical suspicion recorded in the electronic health record; positive multiplex PCR for RSV, SARS-CoV-2, or influenza; and fulfillment of criteria for either upper (URTI) or lower respiratory tract infection (LRTI). * URTI criteria: presence of at least two of the following - rhinorrhea, nasal or sinus congestion, otitis media, pharyngitis, or dry cough - with a normal chest X-ray or CT scan. * LRTI or new pneumonia criteria: cough accompanied by at least one of the following - dyspnea, rhonchi, crackles, wheezing, tachypnea, or hypoxemia - with a new pulmonary infiltrate on chest X-ray or CT scan. Exclusion Criteria: * Patients under palliative care or with a life expectancy of less than 24-48 hours. * Lack of nursing NEWS assessment, or a medical order stating "Do not resuscitate" or "Do not follow NEWS protocol." * Patients vaccinated with an RSV vaccine prior to the acute respiratory infection episode, based on documented RSV vaccination status in the electronic health record (applicable to the later study period only, May 2022-December 31, 2025, coinciding with RSV vaccine availability in Argentina).