Research and analysis

Acute hepatitis B: national enhanced surveillance report January to December 2021

Updated 24 January 2024

Background

The quarterly reporting of enhanced molecular surveillance of acute hepatitis B is based on clinical reports of acute cases to UK Health Security Agency (UKHSA) being entered on HPZone and corresponding samples being submitted to the UKHSA Blood Borne Virus Unit (BBVU) in the Virus Reference Department (VRD) at Colindale.

In 2016, VRD reintroduced anti hepatitis B core avidity testing alongside genotyping of samples from patients diagnosed with acute hepatitis B, a service which is offered free of charge. Hospital microbiology and virology departments are requested to send samples to Colindale for confirmation, avidity testing and genotyping as part of the national enhanced surveillance of acute hepatitis B (see Acute hepatitis B: guide to national enhanced surveillance).

Following the reporting of clusters of acute hepatitis B in 2016, an HPZone Context ‘Acute hepatitis B’ was added for monitoring of acute cases.

Methods

Acute hepatitis B cases recorded in 2 different ways and entered on HPZone between January and December 2021 were extracted. HPZone Context ‘Acute Hepatitis B’ data includes personally identifiable information, which therefore allows for the rapid identification of cases and the requesting of samples directly from laboratories for avidity and molecular characterisation at VRD Colindale.

HPZone data without personally identifiable information (HPZone Dashboard) on acute cases was matched to HPZone Context data using a unique identifier. The ‘Acute Hepatitis B’ Context data was matched to laboratory testing data from VRD using Microsoft Access algorithms comparing combinations of the following variables: surname, first name, date of birth, sex, and NHS number.

Results

Between January and December 2021, 201 cases of acute hepatitis B were reported onto HPZone Dashboard across England (confirmed, probable and possible).

Overall, the cases entered on HPZone Dashboard have been declining since 2011: from 513 in that year to 199 in 2020. Monthly cases since 2010 in England are shown in figure 1. In 2015 there was a slight increase in cases likely caused by the 2015 outbreak of acute hepatitis B in men who have sex with men (MSM) who identify as heterosexual (1).

Figure 1. Cumulative cases of acute hepatitis B in England entered on HPZone Dashboard: 2010 to December 2021. (Note: 2021 data is provisional)

Figure 2 shows the number of cases reported with personal identifiable information through HPZone Context by month. The additional information allows for a letter to be sent to request residual samples directly from laboratories for avidity and molecular characterisation. The dots represent the proportion of samples received from laboratories. Figure 3 shows this distribution by region.

Figure 2. January to December 2021 cases entered onto HPZone Dashboard. The dots (right axis) show the proportion of HPZone Context cases that had a sample forwarded to VRD

Figure 3. January to December 2021 cases entered onto HPZone Context and/or entered onto HPZone Dashboard by UKHSA regions. The dots (right axis) show the proportion of HPZone Context cases that had a sample forwarded to VRD

For cases reported between January to December 2021, in both the HPZone Context data set and the HPZone Dashboard data set, age and sex were reported (99.5%). Where sex was known (200 out of 201) males accounted for 64.0% of cases (128 out of 200). The median age of those with acute HBV was 39 years (IQR: 30 to 53): 42 years (IQR: 31 to 54) for males and 37 (IQR: 26 to 50) for females.

The age distribution by sex is presented in table 1. The highest proportion of cases was seen in those in the 35 to 44 year age group. The highest proportion in males was in the 35 to 44 year group, while in females, highest proportion was in the 15 to 24 year, and the 35 to 44 year, age groups.

Table 1. Number and proportion of acute HBV cases from HPZone Dashboard by sex and age group during January to December 2021

Age group	Female	Male	Unknown	Total
Under 15	3 (4%)	3 (3%)	0 (–)	6 (3%)
15 to 24	15 (21%)	12 (9%)	0 (–)	27 (13%)
25 to 34	13 (18%)	27 (21%)	0 (–)	40 (20%)
35 to 44	15 (21%)	34 (27%)	1 (100%)	50 (25%)
45 to 54	11 (15%)	20 (16%)	0 (–)	31 (15%)
55 to 64	9 (13%)	17 (13%)	0 (–)	26 (13%)
65 and over	6 (8%)	15 (12%)	0 (–)	21 (10%)
Total	72	128	1	201

Avidity testing and molecular characterisation investigations were undertaken on samples linked to cases to confirm the acute hepatitis B diagnosis with additional genotyping and phylogenetic analysis to inform on the diversity of the circulating viruses.

Of the 63 samples submitted to VRD as part of the enhanced surveillance programme, 8 samples (13%) were confirmed to be from individuals with chronic hepatitis B and 27 (43%) were confirmed to be from individuals with acute hepatitis B infection. The avidity testing in 11 samples was classified as undetermined where it was not possible to confidently assign an HBV infection status and 17 samples were not tested.

Not all cases with samples forwarded to VRD could be matched to cases in HPZone Context; this could either be due to a case not being entered on HPZone or it could be due to the case being entered in a previous quarter.

A total of 27 confirmed acute cases could be genotyped during the January to December 2021 quarter; the distribution of genotypes is shown in table 2. Consistent with trends seen in 2019 and 2020, genotype A was the most commonly reported genotype with 63% of cases (2). Additional sub genotype analysis of the A viruses indicated 94% to be A2. The distribution of genotypes seen in UKHSA regions is shown in figure 4.

Table 2. Genotype distribution and proportions of acute hepatitis B cases tested at VRD in January to December 2021

Acute genotype	Number of cases	Proportion of cases
A	17	63%
B	1	4%
C	0	–
D	5	19%
E	3	11%
F	1	4%
Total	27	–

Figure 4. Genotypes of acute samples sent to VRD by UKHSA region*

*Excludes 3 where region was unknown (genotypes A2=1, D5=1 and B3=1).

Discussion

Quarterly publication of enhanced molecular surveillance using matched HPZone and reference laboratory confirmatory and typing data with a regional breakdown allows real-time monitoring of acute hepatitis B transmission. The number of acute hepatitis B cases in January to December 2021 remained low and consistent with annual trends for the same timeframe. Molecular analysis provides insight into the current hepatitis B genotypes circulating in England, although interpretation is limited by the small proportion of samples submitted to VRD. The A2 ‘prisoner variant’ is one of the most common strains and is known to be well-established in the UK MSM population.

Other genotypes can indicate a geographical origin which can help provide an understanding of sources of infection and transmission routes. For example, genotype D is associated with South Asia. Timely assignment of cases to the HPZone Context and improved submission of samples for molecular characterisation will allow for more comprehensive monitoring of acute hepatitis B infection in England.

References

1. Shankar AG, Mandal S, Ijaz S (2016). ‘An outbreak of hepatitis B in men who have sex with men but identify as heterosexual’ BMJ Sexually Transmitted Infections, volume 92 issue 3: page 227.

2. Public Health England (2016). ‘Acute Hepatitis B (England): annual report for 2018’