Comprehensive surveillance data suggest a prominent role of parvovirus B19 infection in Belarus and the presence of a third subtype within subgenotype 1a

Abstract

Human parvovirus B19 (B19V) infection is not notifiable in Belarus and its most common clinical presentation erythema infectiosum (EI) is often difficult to distinguish from other exanthematous diseases. The objective of this study was to provide comprehensive data about EI epidemiology in Belarus based on the serological and molecular investigation of samples from measles and rubella discarded cases collected between 2005 and 2019. Overall, 4919 sera were investigated for IgM antibodies against B19V and the positive cases were analysed according to year, season and age. B19V DNA was amplified by PCR in a total of 238 sera from all over the country, and sequenced for phylogenetic analyses. B19V infection was confirmed in 1377 (27.8%) measles and rubella discarded cases. Two high incidence periods and a seasonal increase of EI between mid-February to mid-July were identified. Children from 4 to 6 and from 7 to 10 years of age represented the largest groups of patients (22.51% and 22.66% of all cases, respectively), followed by adults between 20 and 29 years of age (14.23%). Among the 238 B19Vs sequenced, one belonged to subgenotype 3b and 237 to subgenotype 1a with 81 (34.2%) clustering with subtypes 1a1 and 153 (64.6%) with 1a2. Three strains (1.2%) formed an additional, well-supported cluster suggesting the presence of another subtype of 1a, tentatively named 1a3. The epidemiological and molecular analyses highlighted not only the prominent role of B19V in exanthematous diseases in Belarus, but also suggested a previously underestimated diversity of subgenotype 1a sequences with a third subtype 1a3.

Figure 1

Erythema infectiosum incidence per 100,000 population in Belarus between 2005 and 2019.

Figure 2

Seasonal trend of erythema infectiosum in Belarus calculated over the whole study period (2005–2019).

Figure 3

Proportion of B19V IgM positive patients by age group in Belarus between 2005 and 2019.

Figure 4

Erythema infectiosum incidence rates per 100,000 people of each age group, Belarus, 2005–2019.

Figure 5

Phylogenetic tree based on 994 nt of the NS1/VP1-unique region junction including the B19V sequences from Belarus. Only one representative strain is shown for identical sequences of subtypes 1a1 and 1a2, and the total number of sequences is added behind in brackets; all three sequences of the provisional subtype 1a3 are presented; the subgenotype 3b strain is marked with a black dot. The strains are named with location, epidemiological week and year or with country name and year/years for representative strains of identical sequences isolated at different time points and/or at different locations. The reference sequences are identified by GenBank accession number and name and are marked with an open circle. Only bootstrap values ≥ 70% (1000 replicates) are shown.

Figure 6

Prevalence of B19V 1a subtypes in individual years, Belarus, 2005–2019.

Figure 7

Phylogenetic tree based on 994 nt of the NS1/VP1-unique region junction. All sequences closely related to the 1a3 strains from Belarus available on Genbank were included. The sequences from Belarus are marked with a black dot. Only bootstrap values ≥ 70% (1000 replicates) are shown.