Should patients who have undergone an allogeneic hematopoietic stem‑cell transplant wear surgical masks (and have visitors wear masks) to prevent respiratory infections, and is routine masking also recommended for autologous transplant or other neutropenic patients?

Mask Use for Stem Cell Transplant Recipients

Allogeneic hematopoietic stem cell transplant recipients are at highest risk for respiratory viral infections and should wear surgical masks (along with their visitors) to prevent community-acquired respiratory viruses, particularly during phases II and III post-transplant when cell-mediated immunity is impaired; autologous transplant recipients have lower risk and routine masking is generally not required unless they develop prolonged neutropenia. 1

Risk Stratification by Transplant Type

Allogeneic HSCT Recipients (Highest Risk)

• Allogeneic recipients face substantially elevated risk for respiratory infections throughout all three post-transplant phases, with particular vulnerability during phase II (30-100 days) and phase III (>100 days) when cell-mediated and humoral immunity defects persist. 1

• Community-acquired respiratory viruses (CRVs) including RSV, influenza, parainfluenza, rhinovirus, and human metapneumovirus are critical pathogens during phases II and III, especially among patients with chronic graft-versus-host disease (GVHD). 1

• The risk for respiratory infections is approximately proportional to GVHD severity, with patients experiencing chronic GVHD having impaired reticuloendothelial function and long-lasting immunoglobulin deficiencies that increase susceptibility to viral and encapsulated bacterial pathogens. 1

• Respiratory viral infections cause predominantly late morbidity, with 75.8% of CRV episodes occurring more than 100 days post-HSCT and 45.6% progressing to lower respiratory tract infection (LRTI). 2

• Mortality from respiratory viruses remains significant, with 5.4% of patients dying within 30 days of CRV diagnosis and attributable mortality of 9.4% among infected allogeneic recipients. 2, 3

Autologous HSCT Recipients (Lower Risk)

• Autologous recipients experience more rapid immune system recovery and lower overall infection risk compared to allogeneic recipients, with primary vulnerability limited to phase I (preengraftment, <30 days). 1

• Routine masking is not required for standard autologous transplant patients unless they develop prolonged neutropenia (ANC <500 cells/mm³ for >14 days), at which point they should be managed similarly to higher-risk patients. 4

• The 2-year incidence of symptomatic respiratory viral infections is approximately half that of allogeneic recipients (14% versus 29%), reflecting their more intact immune reconstitution. 5

Specific Respiratory Infection Risks

Viral Pathogens of Concern

• Rhinovirus is the most commonly isolated respiratory virus (47% of CRV episodes), followed by respiratory syncytial virus (32%) and parainfluenza (32%). 2, 6

• RSV infection results in prolonged viral shedding (median 20 days, range 7-84 days) and carries a 21.4% mortality rate among patients who progress to LRTI. 3

• Lower respiratory tract progression occurs in 45-56% of upper respiratory infections, with severe lymphocytopenia (<0.2×10⁹/L) being the strongest independent risk factor for progression. 2, 6, 5

• Concurrent bacterial or fungal infections significantly increase pneumonia risk (100% versus 68%, P=0.023), emphasizing the importance of preventing initial viral acquisition. 6

Timing and Clinical Context

• The majority of CRVs (67%) are diagnosed in the outpatient setting, making patient and visitor masking during clinic visits and at home particularly important. 2

• Human metapneumovirus should be recognized as a serious cause of respiratory infection in HSCT recipients and warrants the same preventive measures as other respiratory viruses. 5

Practical Masking Recommendations

For Allogeneic HSCT Recipients

• Both patients and all visitors should wear surgical masks during phases II and III (30 days through at least 6-12 months post-transplant, or longer if chronic GVHD persists). 1

• Masking should be maintained in all healthcare settings, during clinic visits, and when in public spaces where exposure to individuals with respiratory symptoms is likely. 1

• Healthcare workers and others in contact with HSCT recipients should follow appropriate hand-washing practices in addition to masking, as bacteria and viruses are transmitted via hands. 1

For Autologous HSCT Recipients

• Standard autologous recipients without prolonged neutropenia do not require routine masking beyond the immediate post-transplant period when neutropenia is expected to resolve quickly. 4

• Masking should be implemented if autologous recipients develop prolonged neutropenia (ANC <500 cells/mm³ for >14 days) or other high-risk features. 4

For Other Neutropenic Patients

• Routine masking is not recommended for standard chemotherapy-induced neutropenia of brief duration (<7 days) in non-transplant patients. 4, 7

• Consider masking for patients with severe prolonged neutropenia (ANC <500 cells/mm³ for >14 days or <100 cells/mm³ for 1 week), particularly during respiratory virus season. 4

Common Pitfalls to Avoid

• Do not assume all neutropenic patients require the same level of respiratory precautions; allogeneic HSCT recipients have fundamentally different and more prolonged immune deficits than patients with chemotherapy-induced neutropenia. 1, 4

• Do not discontinue masking precautions at day 100 post-transplant if chronic GVHD is present, as these patients remain at elevated risk for respiratory infections proportional to GVHD severity. 1

• Do not rely solely on masking without emphasizing hand hygiene, which remains the most effective infection-prevention strategy regardless of other precautions. 1, 4

• Do not overlook the importance of visitor masking, as community-acquired respiratory viruses are frequently introduced by family members and friends who may have subclinical infections. 1, 2

• Do not confuse protective environment requirements (HEPA filtration for fungal prevention) with respiratory virus precautions (masking); these address different pathogens and require different interventions. 4