Prolonged outbreak of adenovirus A31 in allogeneic stem cell transplant recipients.
BACKGROUND
An outbreak of human adenovirus (HAdV) A31 occurred from December 2011 to March 2012 at the Center for Allogeneic Stem Cell Transplantation (CAST), Karolinska University Hospital in Sweden. We analyzed the outbreak, the routes of transmission, and report the medical consequences.


METHODS
The medical records of all patients admitted to CAST during the outbreak period were studied. Phylogenetic analysis of the patient HAdV strains was performed by sequencing the hexon gene and the more variable E3 gene.


RESULTS
We identified 9 cases of HAdV A31. Hygiene measures were implemented, but transmission continued for 2 months. All 9 patients had been admitted to the ward, but 2 had no connection in time to other known HAdV A31 cases. DNA sequencing of the patient strains strongly suggested nosocomial transmission. Transplantation was postponed and then cancelled in 1 patient, and 5 patients were treated with cidofovir because of high levels of viremia. In 7 patients, concomitant graft-versus-host disease (GVHD) grade II-V complicated the clinical picture, as it was difficult to distinguish symptoms of GVHD from those of HAdV infection.


CONCLUSIONS
An outbreak of HAdV in HSCT recipients can be difficult to control. Although none of the patients had severe disease, the medical consequences were significant. It is possible that unidentified cases with mild symptoms may have caused continuous transmission at the unit. Regular testing of all patients several weeks beyond the last case identified may be an important measure to control transmission.
Division of Infectious Diseases, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
L
L
Swartling
Department of Virology, Umeå University, Umeå, Sweden.
A
A
Allard
Center for Allogeneic Stem Cell Transplantation, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
J
J
Törlen
Center for Allogeneic Stem Cell Transplantation, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.|Department of Hematology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
P
P
Ljungman
Center for Allogeneic Stem Cell Transplantation, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
J
J
Mattsson
Division of Infectious Diseases, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
E
E
Sparrelid
D000256:Adenoviridae / Q000145:classification* / Q000235:genetics; D000257:Adenoviridae Infections / Q000188:drug therapy / Q000635:transmission* / Q000821:virology*; D000998:Antiviral Agents / Q000627:therapeutic use; D000077404:Cidofovir; D003596:Cytosine / Q000031:analogs & derivatives / Q000627:therapeutic use; D004279:DNA, Viral / Q000235:genetics; D004196:Disease Outbreaks; D006801:Humans; D063065:Organophosphonates / Q000627:therapeutic use; D010802:Phylogeny; D012189:Retrospective Studies; D033581:Stem Cell Transplantation / Q000009:adverse effects*; D013548:Sweden / Q000453:epidemiology; D013997:Time Factors
D000998:Antiviral Agents; D004279:DNA, Viral; D063065:Organophosphonates; D003596:Cytosine; D000077404:Cidofovir
adenovirus A31; outbreak; phylogenetic analysis; stem cell transplantation