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\begin{document}

\title{Epidemiology of herpes simplex virus type 2 in China: Systematic review,
meta-analyses, and meta-regressions}



\author[1]{Chunfu  Zheng}%
\author[2]{Yehua Wang}%
\author[2]{Xumeng Yan}%
\author[3]{Wei Ai}%
\author[4]{Rongyi Chen}%
\author[5]{Yuanxi Jia}%
\author[3]{Chengxin Fan}%
\author[2]{Siyue Hu}%
\author[2]{Yifan Dai}%
\author[2]{Huachen Xue}%
\author[2]{Feifei Li}%
\author[6]{Jinbo Zhai}%
\author[7]{Xuefeng Xia}%
\author[2]{Weiming Tang}%
\affil[1]{University of Calgary Department of Microbiology Immunology and Infectious Diseases}%
\affil[2]{The University of North Carolina at Chapel Hill UNC Project-China}%
\affil[3]{Nanjing Medical University School of Public Health}%
\affil[4]{Guangdong Provincial Dermatology Hospital}%
\affil[5]{Chinese Academy of Sciences Shenzhen Institutes of Advanced Technology}%
\affil[6]{Inner Mongolia Minzu University}%
\affil[7]{GenePlus Technology Co Ltd}%


\vspace{-1em}



  
  \date{June 09, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
\textbf{Background:} Herpes simplex virus type 2 (HSV-2) infection is
prevalent and a significant public health problem. Understanding its
epidemiology will help assess the current HSV-2 prevention efforts and
inform future interventions in China. \textbf{Methods:} We followed
Cochrane and PRISMA guidelines for a systematic review and included
publications published in Chinese and English bibliographic systems
until March 18 \textsuperscript{th}, 2023. We synthesized
seroprevalence, sero-incidence, and proportions of HSV-2 isolated in
genital ulcer disease (GUD) and genital herpes data. We used
random-effects models for meta-analyses and conducted meta-regression to
assess the association between population characteristics and
seroprevalence. \textbf{Results:} Overall, 21,849 articles were
identified, and 457 publications (1,051,035 participants) were included.
A total of 429 studies reported the overall seroprevalence rates (939
stratified measures), 5 reported seroincidence rates, 4 reported overall
proportions of HSV-2 isolation in GUD (8 stratified proportions), and 24
reported overall proportions of HSV-2 isolation in genital herpes (59
stratified proportions). Pooled HSV-2 seroprevalence among overall
populations was 14.9\% (95\% confidence interval (CI): 13.8-16.1\%) and
was 7.9\% (95\% CI: 6.9-8.8\%) among the general population.
Seroprevalence was highest among key populations (e.g., female sex
workers and men who have sex with men) (32.1\% (95\% CI: 27.8-36.5\%)).
Among the general population, we found northeastern regions had a higher
HSV-2 seroprevalence (12.4\%, 95\% CI: 7.8-17.9\%). HSV-2 seroprevalence
also increased with age. The pooled HSV-2 seroincidence rate was 4.3 per
100 person-years (95\% CI: 1.0-7.6). Pooled HSV-2 seroprevalence among
GUD and genital herpes were 45.2\% (95\% CI: 29.0-61.9\%) and 52.8\%
(95\% CI: 46.6-59.0\%), respectively. We also found higher HSV-2
seroprevalence estimates in publications published in English
bibliographic databases than those in Chinese databases (20.5\%
\emph{vs}. 13.6\%, risk ratio=1.10 (1.05-1.14)), indicating a potential
existence of language bias in publication. \textbf{Conclusion:} Around 1
in 12 among the general population and 1 in 7 among all included
populations were infected with HSV-2. The data revealed vulnerability to
HSV-2 infection among higher-risk populations calling for expanding the
intervention to prevent HSV-2 infection. It also revealed
heterogeneities in synthesized HSV-2 prevalence results, suggesting the
necessity to include Chinese bibliographic databases in conducting
systematic reviews and meta-analyses of this topic.%
\end{abstract}%



\sloppy


\textbf{Epidemiology of herpes simplex virus type 2 in China: Systematic
review, meta-analyses, and meta-regressions}

Yehua Wang \textsuperscript{1+}, Xumeng Yan \textsuperscript{1+}, Wei
Ai\textsuperscript{2+}, Rongyi Chen\textsuperscript{3}, Yuanxi
Jia\textsuperscript{4}, Chengxin Fan \textsuperscript{2}, Siyue
Hu\textsuperscript{1}, Yifan Dai \textsuperscript{1}, Huichen
Xue\textsuperscript{1}, Feifei Li \textsuperscript{1}, Jingbo
Zhai\textsuperscript{5}, Xuefeng Xia\textsuperscript{6}, Chunfu
Zheng\textsuperscript{7*}, Weiming Tang \textsuperscript{1,3*}

\textsuperscript{1} University of North Carolina at Chapel Hill
Project-China, Guangzhou, China

\textsuperscript{2} School of Public Health, Nanjing Medical University,
Nanjing, China

\textsuperscript{3}Department of STD Clinic, Dermatology Hospital of
Southern Medical University, Guangzhou, China

\textsuperscript{4} Shenzhen Institute of Advanced Technology, Chinese
Academy of Science, Shenzhen, China

\textsuperscript{5} Key Laboratory of Zoonose Prevention and Control at
Universities of Inner Mongolia Autonomous Region, Medical College, Inner
Mongolia Minzu University, Tongliao, 028000, China

\textsuperscript{6} GenePlus-Beijing Institute, Beijing, China

\textsuperscript{7} Department of Microbiology, Immunology and
Infectious Diseases, University of Calgary, Calgary, Alberta, Canada.

+These authors have contributed equally to this work and share the first
authorship

\textbf{* Correspondence:} Chunfu Zheng (zheng.alan@hotmail.com);
Weiming Tang (weiming\_tang@med.unc.edu).

Keywords: Herpes simplex virus type 2 (HSV-2), Epidemiology, Systematic
review and meta-analysis.

\textbf{Abstract}

\textbf{Background:} Herpes simplex virus type 2 (HSV-2) infection is
prevalent and a significant public health problem. Understanding its
epidemiology will help assess the current HSV-2 prevention efforts and
inform future interventions in China.

\textbf{Methods:} We followed Cochrane and PRISMA guidelines for a
systematic review and included publications published in Chinese and
English bibliographic systems until March 18\textsuperscript{th}, 2023.
We synthesized seroprevalence, sero-incidence, and proportions of HSV-2
isolated in genital ulcer disease (GUD) and genital herpes data. We used
random-effects models for meta-analyses and conducted meta-regression to
assess the association between population characteristics and
seroprevalence.

\textbf{Results:} Overall, 21,849 articles were identified, and 457
publications (1,051,035 participants) were included. A total of 429
studies reported the overall seroprevalence rates (939 stratified
measures), 5 reported seroincidence rates, 4 reported overall
proportions of HSV-2 isolation in GUD (8 stratified proportions), and 24
reported overall proportions of HSV-2 isolation in genital herpes (59
stratified proportions). Pooled HSV-2 seroprevalence among overall
populations was 14.9\% (95\% confidence interval (CI): 13.8-16.1\%) and
was 7.9\% (95\% CI: 6.9-8.8\%) among the general population.
Seroprevalence was highest among key populations (e.g., female sex
workers and men who have sex with men) (32.1\% (95\% CI: 27.8-36.5\%)).
Among the general population, we found northeastern regions had a higher
HSV-2 seroprevalence (12.4\%, 95\% CI: 7.8-17.9\%). HSV-2 seroprevalence
also increased with age. The pooled HSV-2 seroincidence rate was 4.3 per
100 person-years (95\% CI: 1.0-7.6). Pooled HSV-2 seroprevalence among
GUD and genital herpes were 45.2\% (95\% CI: 29.0-61.9\%) and 52.8\%
(95\% CI: 46.6-59.0\%), respectively. We also found higher HSV-2
seroprevalence estimates in publications published in English
bibliographic databases than those in Chinese databases (20.5\%\emph{vs}
. 13.6\%, risk ratio=1.10 (1.05-1.14)), indicating a potential existence
of language bias in publication.

\textbf{Conclusion:} Around 1 in 12 among the general population and 1
in 7 among all included populations were infected with HSV-2. The data
revealed vulnerability to HSV-2 infection among higher-risk populations
calling for expanding the intervention to prevent HSV-2 infection. It
also revealed heterogeneities in synthesized HSV-2 prevalence results,
suggesting the necessity to include Chinese bibliographic databases in
conducting systematic reviews and meta-analyses of this topic.

\textbf{Funding:} This study was researchers-initiated and did not
receive any funding support

\textbf{Conflict of interest:} None

\textbf{Word count:} 3696

\textbf{Epidemiology of herpes simplex virus type 2 in China: Systematic
review, meta-analyses, and meta-regressions}

\textbf{Introduction}

Herpes simplex virus type 2 (HSV-2) is an incurable and recurring
sexually transmitted infection.\textsuperscript{1} Often asymptomatic,
people with HSV-2 can transmit the virus to their sexual partners
without awareness of their infection.\textsuperscript{2} It also
increases the risk of acquiring and transmitting the Human
immunodeficiency virus (HIV).\textsuperscript{3,4} Given its contingency
and impact on life quality and
well-being,\textsuperscript{5}understanding the epidemiology of HSV-2 is
essential for informing future prevention. Also, considering its synergy
with HIV, reducing HSV-2 infection is beneficial to the goal of ending
STI epidemics as major public health concerns by
2030.\textsuperscript{6}

The latest estimate of HSV-2 global prevalence in 2016 was 13.2\% (491
million) among people aged 15-49 worldwide.\textsuperscript{7} Recent
meta-reviews have reported a wide range of prevalence estimates from
different geographical regions, including 37.3\% in sub-Saharan
Africa,\textsuperscript{8} 20.6\% in Latin
America,\textsuperscript{9}15.4\% in Canada, Australia, and New
Zealand,\textsuperscript{10} 12.4\% in Europe,\textsuperscript{11}
12.1\% in Asia,\textsuperscript{12} and 5.1\% in the Middle East and
North Africa among the general population.\textsuperscript{13}
Seroprevalences of HSV-2 among key populations such as male sex
workers(MSW), men who have sex with men (MSM), and female sex workers
(FSW) are substantially higher across regions, ranging from 20.6\% to
74.8\% for FSW and from 18.3\% to 54.6\% for MSM and
MSW.\textsuperscript{8-13}

Despite the existing literature, a comprehensive overview of HSV-2
epidemiology and trends among different populations in China is limited,
calling for a systematic review and meta-analysis. A meta-analysis in
Asia reported a pooled HSV-2 seroprevalence of 9.3\% among the general
population.\textsuperscript{12} However, it only included literature
identified from English bibliographic databases, which may incur
language bias.\textsuperscript{14} We also identified two additional
meta-analyses that focused on specific populations in China, such as the
MSM population with a pooled prevalence of 9.4\%,
\textsuperscript{15}and the FSW population with a 15.8\% HSV-2
prevalence.\textsuperscript{16} These reviews included a small portion
of the existing studies, which is quite limited. Our study aims to fill
this gap and provide a more comprehensive and up-to-date estimate of the
HSV-2-related outcomes (e.g., prevalence and incidence) among various
populations in China by synthesizing literature published in Chinese and
English and generating estimates by different groups and subpopulations.

\textbf{Methods}

The study protocol was registered in PROSPERO (PROSPERO ID:
CRD42023408108).

\textbf{Data sources and search strategy}

This systematic review was conducted under the guidance of the Cochrane
Collaboration Handbook.\textsuperscript{17} We reported the findings
following the Preferred Reporting Items for Systematic Reviews and
Meta-Analyses (PRISMA) statement.\textsuperscript{18} We included four
bibliography databases, including PubMed, Embase, China National
Knowledge Infrastructure (CNKI), and Wanfang, as the sources.
Considering the limited publication coverage in Chinese in PubMed and
Embase, we included two major Chinese bibliography databases, CNKI and
Wanfang.\textsuperscript{19} We searched the publications till March
18\textsuperscript{th}, 2023.

\textbf{Eligibility criteria}

We included the publications that reported primary data related to HSV-2
for any of the four outcomes (1) seroprevalence, which was defined by
the proportion of the included population who tested HSV-2 seropositive;
(2) seroincidence or seroconversion, defined as the occurrence of HSV-2
infections per person-time; (3) the proportion of genital ulcer disease
(GUD) cases in which HSV-2 was isolated as its cause; (4) the proportion
of genital herpes cases in which HSV-2 was isolated as its cause.

We excluded case reports, case series, commentaries, reviews, and
publications without access to the full text. We also excluded the
studies that involved less than 10 participants. Those studies reporting
HSV-related outcomes (including both HSV-1 and HSV-2) were excluded if
we could not extract HSV-2 outcomes. If one study only reported HSV-2
prevalence from infants younger than six months, we excluded it due to
the parental source antibody.\textsuperscript{20}

\textbf{Literature screening and data extraction}

For each publication, any two of the eight reviewers (FL, AW, XY, YW,
SH, YD, HX, CF) independently screened thetitles, abstracts, and full
texts and identified eligible publications for data extraction. In case
of disagreements between the two reviewers, a third reviewer (WT and YW)
was consulted for reconciliation if an agreement was not reached.

We extracted the variables containing information on publication year,
data collection time, methods, testing assay, study population type,
age, sex, sample size, and relevant study outcomes. We used pre-defined
population types and risk factors to conduct stratified analyses of our
study outcomes. The definition of population type and risk factors was
included in the supplementary materials (Supplementary Box S1 and S3).

\textbf{Quality assessment}

We referred to a previously published study in assessing the study
quality.\textsuperscript{21} WT (University of North Carolina at Chaple
Hill) is the team's leading HSV-2 assay analysis assessment expert.
Study precision was categorized into high and low based on the sample
size (low: \textless{}200 vs. high [?]200). The risk of bias was assessed
based on the sampling method (probability-based vs.
non-probability-based) and response rate (low: \textless{}80\% vs. high
[?]80\%). We consider studies using existing medical records as
non-probability-based studies and of high response rates.

\textbf{Meta-analyses}

We used the random-effects model to conduct the meta-analyses and to
pool the proportions of HSV-2 positive cases.\textsuperscript{22} We
used the Freeman-Tukey double arcsine transformation by specifying the
command sm=``PFT'' in the analysis.\textsuperscript{23} We presented
Cochran's Q statistic to assess the effect size
heterogeneity.\textsuperscript{24} I\textsuperscript{2} was used to
measure the between-study heterogeneity. We also presented prediction
intervals, defined as the 95\% confidence interval of the distribution
of true HSV-2 seroprevalence around the estimation.

The pool results were stratified by different characteristics, including
age groups, gender, year of data collection, and study sites. We mapped
the pooled seroprevalence in the unit of provinces in China to
demonstrate the geographic difference in the HSV-2 disease burden.

\textbf{Meta-regression}

We conducted univariate and multivariable random-effects meta-regression
analyses to assess the association between log-transformed
seroprevalence and pre-decided factors. All variables in the univariate
model whose p-value was less than 0.1 were included in the multivariable
analyses. A \emph{P} -value \textless{} 0.05 (two sides) in the
multivariable analysis indicated a statistically meaningful association.

\textbf{Language bias assessment}

To compare the synthesized HSV-2 prevalence between the studies
published in Chinese and English bibliographic databases, we stratified
the study population into the general, intermediate-risk, and
higher-risk populations. We used the meta-regression to assess the
association between HSV-2 seroprevalence and language of the
bibliography systems using relative risk as the measure. We hypothesize
there would be a difference in HSV-2 seroprevalence estimation between
the studies identified from Chinese and English bibliographic databases
suggesting the existence of publication bias.\textsuperscript{25}

``Publication'' refers to a document reporting any outcome measure,
while a ``study'' refers to details of a specific outcome measure. One
publication might contain multiple study outcome measures (e.g.,
subgroup analyses). Duplicate or overlapping studies were included only
once.

Literature screening was completed by
Covidence.\textsuperscript{26}Publication management was completed by
Endnote X9.\textsuperscript{27}Data extraction was completed by
Microsoft Office Excel 2016. Meta-analyses, meta-regression, and mapping
were conducted in R, version 4.3.0, using the `meta' and `metafor'
packages.\textsuperscript{28,29}

\textbf{Results}

\textbf{Search results and scope of evidence}

We identified 21,849 publications from four bibliographic databases
(PubMed 1,125, Embase 14,243, CNKI 2,387, and Wanfang 4,094). After
excluding duplicate references, 20,830 publications remained. Based on
the abstract and title screening, 19,643 publications were further
excluded. As 16 publications were not retrieved for full text, 1,171
publications entered full-text screening. Of these, an additional 714
publications were excluded, leaving the rest 457 publications that met
eligibility criteria. The majority of the studies were conducted in
Central Southern China (30.6\%), Southeastern (28.7\%), and Southwestern
China (17.5\%).

In total, 429 included publications reported the overall seroprevalence
rates (939 stratified measures), 5 reported seroincidence rates, four
reported the overall proportions of HSV-2 isolation in GUD (8 stratified
proportions), and 24 reported the overall proportions of HSV-2 isolation
in genital herpes (59 stratified proportions). The PRISMA flowchart of
article selection is summarized in \textbf{Figure 1} . For study
settings, 80.0\% of the studies involved more than 200 participants, and
91.2\% used non-probability-based methods. About two-thirds of studies
had more than 80\% response rates.

\textbf{Seroincidence overview}

Seroincidence rates are summarized in Table S1. More than half of the
studies were longitudinal cohort studies (n=4; 80.0\%) with follow-up
durations ranging from 6 months to 12 months. In all populations, HSV-2
seroincidence ranged between 3.8 to 21.9 per 100 person-years, with the
highest reported seroincidence among FSWs. The pooled seroincidence rate
was 4.3 per 100 person-years (95\% CI: 1.0-7.6).

\textbf{Seroprevalence overview}

More than 80\% of the studies reporting seroprevalence measures (n=429)
were published after 2005 (n=352, 82.1\%). Most studies used convenience
sampling (n=374, 87.2\%). All seroprevalence measures are summarized in
Table 1 and Table 2. Most studies collected data during the
21\textsuperscript{st} century (2000-2010: 42.0\%; after 2010: 42.4\%).

Pooled means of HSV-2 seroprevalence among overall populations was
14.9\% (n=947, 95\% confidence interval (CI): 13.8\%-16.1\%). Pooled
mean HSV-2 seroprevalence was lowest at 7.8\% (n=10, 95\% CI:
2.6\%-15.2\%) among other populations, followed by 7.9\% (n=256, 95\%
CI: 6.9\%-8.8\%) among the general population, 16.7\% (n=16, 95\% CI:
12.7\%-21.1\%) among intermediate-risk populations, 23.1\% (n=73, 95\%
CI: 20.5\%-25.8\%) among STI clinic attendees and symptomatic
populations, and 26.0\% (n=14, 95\% CI: 20.0\%-32.4\%) among people
living with HIV (PLWH) and their couples, and 32.1\% (n=80, 95\% CI:
27.8\%-36.5\%) among those at high risk. Across all populations except
for HIV-positive and individuals in HIV-discordant couples, women had
higher pooled mean seroprevalence than men (\textbf{Table 1} ).

\textbf{Table 2} shows stratified subpopulations in the general
populations and their range of seroprevalence. Pooled mean
seroprevalence was higher in the Northeast region at 12.4\% (n=18, 95\%
CI: 7.8-17.9\%), followed by the Central-southern region at 10.5\%
(n=126, 95\% CI: 8.4-12.7\%). The pooled mean seroprevalence increased
with age from the age group 20-29 years. Pooled mean seroprevalence was
5.6\% (95\% CI: 4.0-7.3\%) among 20-29-year-olds (n=74), followed by
8.2\% (95\% CI: 6.0-10.6\%) among 30-39-year-olds (n=50), 8.9\% (95\%
CI: 5.1\%\%-13.5\%) in those aged 40-49 years (n=60), 15.3\% (95\% CI:
12.0-19.0\%) in those aged 50-59 years (n=14), and 20.0\% (95\% CI:
9.9-32.3\%) in those aged [?]60 years (n=9). Pooled mean seroprevalence
decreased with the year of data collection and year of publication.
Pooled mean seroprevalence was 15.1\% (95\% CI: 8.3-23.4\%) for data
collected in 2000 and earlier (n=30), followed by 6.9\% (95\% CI:
5.6-8.3\%) during 2001-2010 (n=205) and 6.7\% (95\% CI: 5.7-7.8\%) after
2010 (n=231). For year of publication, pooled mean seroprevalence was
10.7\% (95\% CI: 7.2-14.7\%) in 2005 and earlier (n=71), followed by
8.1\% (95\% CI: 6.7-9.6\%) during 2006-2015 (n=258) and 6.5\% (95\% CI:
5.6-7.4\%) after 2015 (n=175).

High and significant heterogeneity was found between studies (p-value
\textless{}0.001, I\textsuperscript{2}\textgreater{}50\%). Forest plots
of different meta-analyses are displayed in Figure S1-S2.

The heatmap in \textbf{Figure 2} shows that HSV-2 seroprevalence varied
across different provinces in China, with higher HSV-2 seroprevalence in
Jilin, Liaoning, and Yunnan Provinces.

\textbf{Meta-regression results}

The results of univariate and multivariable meta-regression analyses are
summarized in Table 3. We performed two multivariable models, the second
multivariable model replacing the categorical variable of ``year of data
collection'' in the first multivariable model with another temporal
variable of ``year of publication''.

The first multivariable model explained 47.7\% of the variation in
seroprevalence (Table 3). Compared to general populations, FSWs had the
highest HSV-2 seroprevalence with an adjusted risk ratio (ARR) of 1.66
(95\% CI: 1.58-1.75), followed by drug users (ARR=1.53, 95\% CI:
1.39-1.70), PLWH and HIV-negative individual in HIV discordant couples
(ARR=1.22, 95\% CI: 1.12-1.32), STI clinic attendees (ARR=1.20, 95\%CI:
1.15-1.25), intermediate-risk populations (ARR=1.13, 95\% CI: 1.05-1.22)
and MSM/MSWs (ARR=1.09, 95\% CI: 1.03-1.16).

Compared to those aged \textless{}20 years, HSV-2 seropositivity
increased with age and was highest in those aged [?]60 years (ARR=1.22,
95\% CI: 1.11-1.36). People living in the Northeast have the highest
risk of HSV-2 (ARR=1.30, 95\% CI: 1.21-1.40) than those living in the
North, followed by the Southwest (ARR=1.10, 95\% CI: 1.04-1.16) and
Central-southern regions (ARR=1.10, 95\% CI: 1.04-1.16). Men have a
similar HSV-2 seroprevalence as women (ARR=0.96, 95\% CI: 0.92-1.01).
Studies that used PCR as an assay reported lower HSV-2 seroprevalence
than those using ELISA.

Studies with larger sample sizes and non-probability sampling reported
lower seroprevalence. Studies with lower response rates reported higher
seroprevalence. Compared to data collected before 2000, data collected
during 2001-2010 (ARR=0.88, 95\% CI: 0.83-0.94) and after 2010
(ARR=0.91, 95\% CI: 0.85-0.96) had lower HSV-2 seroprevalence.

The second model explained 45.7\% of the variation in HSV-2
seroprevalence, yielding similar results to the first model. The
seroprevalence did not vary by year of publication (\textbf{Table 3} ).

\textbf{HSV-2 isolation in GUD and genital herpes}

The proportions of people with HSV-2 virus isolation in clinically
diagnosed cases of genital ulcer disease and genital herpes are
presented in \textbf{Table 4} . Most studies on HSV isolation in GUD
(n=3, 75.0\%) and in genital herpes (n=17, 70.8\%) were published after
2005.

In patients with GUD (n=8), HSV-2 seroprevalence ranged from 12.1\% to
70.9\%, with a median of 55.3 \%. Pooled seroprevalence was 45.2\% (95\%
CI: 29.0-61.9\%), with 48.2 \% (95\% CI: 22.0-74.9\%) among women and
42.2\% (95\% CI: 21.1-64.8\%) among men.

In genital herpes cases (n=59), HSV-2 seroprevalence ranged from 15.4 \%
to 100.0\%, with a median of 48.3\%. Pooled seroprevalence was 52.8\%
(95\% CI: 46.6-59.0\%), with 55.2 \% (95\% CI: 40.1-69.8\%) among women
and 47.5\% (95\% CI: 31.8-63.5\%) among men.

Significant heterogeneity was found between studies (\emph{P} -value
\textless{}0.001, I\textsuperscript{2}\textgreater{}95\%). Forest plots
of the proportion of HSV-2 isolated in GUD and genital herpes are
presented in Figure S2.

\textbf{Language bias between publications identified in Chinese and
English bibliographic databases}

\textbf{Table 5} summarizes the differences in pooled HSV-2
seroprevalence between publications identified in Chinese and English
bibliographic databases. More publications were collected in Chinese
bibliographic databases (371 identified in CNKI and Wanfang \emph{vs} .
58 identified in PubMed and Embase). HSV-2 seroprevalence in Chinese
publications ranged from 0.0\% to 85.3\%, with a median of 11.3\%, and
in English publications ranged from 0.0\% to 88.0\%, with a median of
15.6\%. Pooled HSV-2 seroprevalence was higher among studies identified
in English than in Chinese (20.5\% \emph{vs} . 13.6\%).

For intermediate-risk populations and drug users, we observed a higher
synthesized seroprevalence in publications published in Chinese than in
English bibliographic databases (22.1\% \emph{vs} . 9.6\%,
63.1\%\emph{vs} . 35.5\%, respectively). The results of the
meta-regression analysis also supported this observation (RR=0.84, 95\%
CI: 0.76-0.93, RR=1.11, 95\% CI: 1.04-1.20, respectively). Within FSWs
and MSM/MSWs, HSV-2 seroprevalence was significantly higher in
publications published in English compared to those published in Chinese
(RR=1.21, 95\% CI: 1.10-1.33, RR=1.11, 95\% CI: 1.04-1.20,
respectively). However, within general populations, STI clinic attendees
and symptomatic populations, and HIV-positive individuals and
individuals in HIV-discordant couples, there was no significant
difference in HSV-2 seroprevalence between publications identified from
Chinese and English bibliographic databases.

\textbf{Quality assessment}

Table S12 summarizes the quality assessment of 429 seroprevalence
studies. Of these, 356 studies (83.0\%) had high precision, 30 studies
(7.2\%) had low ROB in the sampling method domain, and 290 studies
(67.6\%) had low ROB in the response rate domain. Only 17 studies
(4.0\%) had low ROB in both quality domains, and 126 studies (29.4\%)
had high ROB in both quality domains.

\textbf{Discussion}

This is a comprehensive systematic assessment of HSV-2 epidemiology in
China. We included publications in Chinese and English major
bibliography databases and involved over one million study participants.
This study has added to the existing literature by providing a most
up-to-date, comprehensive picture of HSV-2 epidemiology in China,
mapping the Chinese provincial level of HSV-2 seroprevalence
differences, and investigating language bias between publications
identified from Chinese and English databases. Around 1 out of 12 people
in the general population were infected by HSV-2. Stratified by study
populations and geographic regions, we observed higher HSV-2 disease
burden among higher-risk populations such as FSW and participants from
northeastern China, calling for more preventive interventions for these
populations. By comparing the HSV-2 prevalence synthesized from Chinese
and English databases, we found a higher overall HSV-2 prevalence from
English bibliographic databases than Chinese, indicating the existence
of language bias and implying the importance of including both Chinese
and English publications in the review.

The HSV-2 seroprevalence among the general population is 7.9\%
(6.9-8.8\%), similar to the overall prevalence of HSV-2 in
Asia,\textsuperscript{21} lower than in Europe, Sub-Saharan Africa, and
Australia but higher than the Middle East and North
Africa.\textsuperscript{8,10,12,13,30} With other regions whose
prevalence was flat\textsuperscript{8} or
increasing\textsuperscript{10,11}, we observed the HSV-2 prevalence in
China reduced by about 2\% every five years, which could be attributed
to better STI clinic access and improved STI education among the general
population nationwide.\textsuperscript{31,32} Stratified by sex, we
observed comparable HSV-2 prevalence between men and women. However,
among other populations, we found a higher HSV-2 seroprevalence among
women than men, especially higher-risk populations, with the
seroprevalence significantly higher among FSW than MSM (52.1\% \emph{vs}
. 12.2\%), which revealed on the one hand, sustained HSV-2 transmission
among this population\textsuperscript{33} and on the other hand, the
importance of continuing healthcare and behavioral intervention to
reduce HSV-2 infection among the populations vulnerable to HSV-2
infection. Geographically, we found that the Northeastern region
(Liaoning, Jilin, and Heilongjiang) had the highest HSV-2 prevalence due
to the high proportion of STI clinic attendees with suspected genital
herpes symptoms and MSM living with HIV within this sample
(10,202/15,904, 64.1\%). Stratified by age group, we observed a steady
increase of HSV-2 prevalence with age, consistent with increasing
cumulative exposure risk to the virus over the sexual life span and
incurability of HSV-2. The assessment of HSV-2 risk factors through
meta-regression confirmed the observations in synthesized
seroprevalences: populations of higher vulnerability to HSV-2 had higher
HSV-2 prevalence as earlier studies had higher HSV-2 prevalence than
later studies.

We found heterogeneities in HSV-2 seroprevalence estimation and study
population composition between English and Chinese bibliographic
databases, indicating language bias. First, from the estimation
perspective, the overall HSV-2 seroprevalence was significantly higher
from English databases than Chinese databases (20.5\% \emph{vs} .
13.6\%, RR=1.10 (1.05-1.14)). Stratified by risk levels, although we
found comparable HSV-2 seroprevalence estimation among the general
population, the HSV-2 seroprevalence estimation was significantly higher
among higher-risk populations such as FSW and MSM/MSM in English
databases. Second, the composition of the study population significantly
differed between the publications identified from English and Chinese
databases. The sample size of general populations in publications from
Chinese databases is more than 15-fold that from English bibliography
databases, mainly attributable to the large-scale toxoplasmosis, rubella
cytomegalovirus, herpes simplex, and HIV (TORCH) screening among
pre-pregnancy and pregnancy women in clinical and community settings.
Meanwhile, the sample size of the higher-risk population in English
databases accounted for one-third of the overall identified sample size,
compared to around 3\% in Chinese databases. Third, Chinese publications
were more geographically diverse, providing HSV-2 seroprevalence not
just in southern China (e.g., Guangdong and Yunnan) but around the
country. These observations might be due to several reasons. First, the
regular TORCH screening results among the general population were harder
to be published in journals published in English bibliographic databases
than in Chinese databases.\textsuperscript{34} Second, higher-risk
populations had higher HSV-2 vulnerabilities and potentially higher
public health significance.\textsuperscript{35} Investigators promoted
their results in journals published in English databases for wider
attention and higher citation.\textsuperscript{36} Interestingly, on the
other hand, we found lower HSV-2 prevalence estimation among
intermediate-risk populations and drug users. The sample sizes and
numbers of the study were much lower than those of higher-risk
populations, which indicates an unmet study need for these populations.
These observations indicate a potential existence of language bias by
only including publications published in English bibliography databases
in the review. Considering the huge quantity and varying quality, most
Chinese journals have yet to be published in English bibliographic
databases.\textsuperscript{37} The synthesized results might be
distorted by restricting publications to English-language only in
literature searching.\textsuperscript{38} Previous studies have shown
that positive results in randomized controlled trials are more likely to
be published and published in English bibliographic databases,
potentially leading to overestimating the drugs' effectiveness. The
Cochrane Handbook for Systematic Reviews and the United States Institute
of Medicine Guidelines for Systematic Reviews recommends including
non-English-language literature published in English bibliographic
databases in the review.\textsuperscript{17,39} Our study revealed that
this might not be enough to eliminate the language bias if not including
non-English bibliographic databases in the review. As a result, it could
y lead to misinterpretation of the disease's unmet needs and a
suboptimal distribution of public health resources in HSV-2 prevention
across different populations.

There are some limitations to be noted. First, we should have included
all Chinese bibliographic databases in the literature search scope.
There are other databases, such as Weipu Database. However, we have
included the two most popular Chinese bibliographic databases in this
review and have yet to observe differences regarding the impact of
journals published in different Chinese databases. Thus, the potential
publication bias of excluding other Chinese databases is minimal.
Second, due to heterogeneities in variable categorization (such as age
group), some studies' subgroups cannot be extracted and are categorized
into the mixed group or other populations. These studies' information
was not fully utilized. However, the synthesized results did not differ
significantly from the categorized groups' results. The overall
estimation should be robust to these heterogeneities in variable
categorization. Third, the current included studies, 29.4\% of them had
high ROB in both quality domains, and only 4.0\% of the studies had low
ROB in both domains, which implies a space for future studies to employ
probability-based sampling methods to improve study quality. Fourth, we
only presented the synthesized results for studies across different
regions. However, there were heterogeneities regarding the study
population. For example, in some regions, we identified more studies
among higher-risk populations than in other regions, which could inflate
the HSV-2, which calls for caution in interpreting the current results
prevalence in this region.

\textbf{Conclusion}

Around 1 in 12 among the general population and 1 in 7 among all
included populations were infected with HSV-2, which calls for more
education to increase HSV-2 awareness and preventive intervention to
curb the transmission of HSV-2. Regarding the language bias of HSV-2
epidemiology, it is necessary to include Chinese bibliographic databases
in the reviewing scope to obtain a more comprehensive picture of HSV-2
infection for various populations and geographic regions and to extract
these figures to reduce the language bias of this topic.

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\verb`To be submitted HSV meta maintext figures.docx`  available at \url{https://authorea.com/users/577949/articles/657193-epidemiology-of-herpes-simplex-virus-type-2-in-china-systematic-review-meta-analyses-and-meta-regressions}

\textbf{Hosted file}

\verb`To be submitted HSV meta maintext tables.docx`  available at \url{https://authorea.com/users/577949/articles/657193-epidemiology-of-herpes-simplex-virus-type-2-in-china-systematic-review-meta-analyses-and-meta-regressions}

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