Observational Data on Parvovirus B19 Cases in Patients with Red Cell Disorders in the United Kingdom from 2023-2024

Parvovirus B19 infection causes a variable clinical picture depending on the host’s immune and haematological state. In situations where there is ineffective erythroid production including haemoglobinopathies and red cell membranopathies, it is well documented that the virus can cause temporary red cell aplasia which can lead to severe anaemia. In the UK there are cyclical peaks of infection rates every 3-4 years. Towards the end of 2023 and during 2024, the UK has seen an increase in cases along with other European countries. Here we present demographic data and the clinical course of parvovirus B19 cases from 2023-2024 within our population of red cell disorders in the UK.

A simple online questionnaire was devised and distributed to clinicians via the UK haemoglobinopathy network to capture the demographics and clinical outcomes of patients with red cell disorders who were infected with parvovirus B19 between June 2023 - July 2024. Parvovirus infection was confirmed with either a positive parvovirus PCR or parvovirus IgM antibody.

Data on 100 cases was collected. 49% of cases were female. The median age of the cases was 9.5 years old. 84 of the patients had sickle cell disorder (66 HbSS, 16 HbSC, 2 compound heterozygous HbS/beta-thalassemia), 12 had hereditary spherocytosis, 2 patients had non-transfusion dependent thalassemia, 1 had pyruvate kinase deficiency and 1 had autoimmune haemolytic anaemia. 88% of patients had no other recorded comorbidities.

For the patients with sickle cell disorder, 35 out of the 84 patients were not on any disease modifying therapy, 44 were on hydroxycarbamide, 2 patients were on regular automated exchanges and the remaining patients were on either top up transfusions or a combination of voxelotor and hydroxycarbamide.

Most cases recorded were admitted in May and June 2024, likely reflecting clinician recall of recent cases. There were no deaths. 16 (17.3%) cases required hospital care in a high dependency (HDU) or intensive care unit (ICU), with 8 cases requiring intensive care. 4/16 (25%) of patients with HbSC required HDU or ICU admission vs 11/66 (16.6%) with HbSS. 1 patient with hereditary spherocytosis required ICU care. 7 of these cases required no organ support, 4 required invasive ventilation, 2 required non invasive ventilation, 2 required multi-organ support (ventilatory, cardiovascular, haemofiltration) and 1 patient required haemofiltration.

Data on the presenting haemoglobin was available for 98/100 patients, the median presenting haemoglobin was 5.45g/dL (1.3g/dL-13.8g/dL). The median presenting absolute reticulocyte count was 20.5 x 10^9 (1.1-337.9 x10^9) derived from data from 71 out of the 100 patients. Additional cytopenias were present in 42/100 patients. 25 patients were neutropenic with a median neutrophil count of 0.9 x 10^9, 26 were thrombocytopenic with a median platelet count of 82 x 10^9 and 14 were lymphopenic with a median count of 0.9 x 10^9.

83 out of 100 patients required packed red cells. 79 received simple top up transfusions, the remainder required a red cell exchange. 2 patients were treated for fat embolism syndrome with a red cell exchange and 5 days of plasma exchange, one of these patients was also given intravenous immunoglobulin (IVIG) and the other was given cryoprecipitate and FFP transfusions to treat DIC, both were HbSC. Intravenous immunoglobulin (IVIG) was also given in 2 other patients along with a top up transfusion due to previous delayed haemolytic transfusion reactions.

Clinicians had a suspicion of supra-added infection in 21 out of 100 cases, in 5 cases there was clinical symptoms or radiological changes suggestive of a chest infection. 5 patients had no clear source of infection and 6 patients had a co-existing viral infection (Bocavirus, COVID, EBV, adenovirus and 2 cases of rhinovirus). 4 of these 21 cases were recorded as being neutropenic.

Here we report 100 cases of parvovirus B19 infection in patients in the UK who have a red cell disorder in between June 2023 and July 2024. 81% of the patients required blood products. A significant proportion (17.3%) of cases required critical care (ICU or HDU). The greater proportion of patients with HbSC (25%) requiring critical care vs HbSS(16.6%) could indicate that patients with HbSC are more vulnerable to developing a more severe disease course. The data collected over 1 year demonstrates that parvovirus B19 infection presents a significant risk to this cohort of patients.