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We prospectively assessed 49 coronavirus disease cases in Guangdong, China, to estimate the frequency and duration of detectable severe acute respiratory syndrome coronavirus 2 RNA in human body fluids. The prolonged persistence of virus RNA in various body fluids may guide the clinical diagnosis and prevention of onward virus transmission.

Defining the immune dynamics of Japanese encephalitis (JE) in healthy individuals is crucial for assessing population susceptibility and evaluating the effectiveness of vaccinations. We conducted a cross-sectional serological survey of anti-JEV IgG antibodies and anti-JEV neutralizing antibodies (nAbs) in Guangzhou City, Zhanjiang City and Heyuan City of Guangdong Province, China. A total of 691 participants were included from 2018-2022, among whom 50 were dengue IgG antibody positive and 641 were dengue IgG antibody negative. In the total population, the anti-JEV IgG antibody positivity rate detected by enzyme-linked immunosorbent assay (ELISA) was 51.37% (95% CI: 47.64-55.11%), and the neutralizing antibody positivity rate detected using the microneutralization test (MNT) was 73.22% (95% CI: 69.92-76.54%). Among the 641 dengue IgG antibody-negative subjects, the anti-JEV IgG antibody positivity rate by ELISA and the neutralizing antibody positivity rate by MNT were 48.05% (95% CI: 44.17-51.93%) and 72.07% (95% CI: 68.59-74.56%), respectively. Comparable geographical seroprevalences of either anti-JEV IgG or neutralizing antibody were observed in Guangzhou City, Heyuan City and Zhanjiang City, respectively (49.52% vs. 48.04% vs. 47.45%, 65.71% vs. 70.46% vs. 76.47%, respectively). Antibody positivity rates in all age groups exhibited a U-shaped curve, with the lowest rate occurring in the 7-18-year-old age group. With respect to the vaccine dose, the anti-JEV nAb positivity rate and geometric mean titer (GMT) detected by MNT were higher in those who received two doses of live attenuated vaccine than in those who received one dose or 0 doses (80.57% vs. 55.81% vs. 55.09% and 25.92 vs. 12.19 vs. 16.47, respectively). In the 641 dengue IgG antibody-negative subjects, moderate consistency between the MNT and ELISA results was observed (Kappa = 0.47, rs = 0.76). The high seroprevalence in participants indicated a neglected transmission of JE, which highlights the importance of strengthening the surveillance of JEV in this area. The vaccination program against JEV is highly needed because of immune gaps in adults, e.g., boosters for adults aged 7-39 years.

Serological surveys of mumps are important for estimating susceptibility in the population and for evaluating the effectiveness of current vaccination strategies. A cross-sectional serological survey using an enzyme-linked immunosorbent assay was conducted on 5,147 participants in Guangdong, China, to evaluate the immunological effects of 2 doses of measles-mumps-rubella vaccine. In accordance with the instructions of the ELISA kit, the final readings represent the anti-mumps antibody titers, which are expressed in \"NovaTec units\". Of the 5,147 participants, 3,888 were positive for mumps IgG antibodies, with a seroprevalence of 75.54% (95% CI: 74.34%-76.71%). For each age group, the mumps IgG seroprevalence rates were 74.40%, 89.02%, 85.58%, 68.60%, 69.28%, 78.42%, and 80.63% for those <8 months, 8 months-2 years, 3-5 years, 6-17 years, 18-39 years, 40-59 years, and>=60 years, respectively. In terms of the percentage decreases in anti-mumps antibody titers, in the population receiving the 1-dose vaccine, there was a mean decrease of 2.06% per year. In the population receiving 2 doses of the vaccine, the mean annual decreases were 10.33% and reached protective thresholds of approximately 12.3 years. The high mumps seroprevalence in the unvaccinated population revealed neglected hidden mumps infections. A time-lapse assay of IgG antibodies indicated that the mumps vaccine provided protection for one decade, which highlights that booster vaccinations may be needed in adults.

Background From 2022 to 2023, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused by Omicron variants spread rapidly in Guangdong Province, resulting in over 80% of the population being infected. Results To investigate the levels of neutralizing antibodies (NAbs) in individuals following the rapid pandemic and to evaluate the cross-protection against currently circulating variants of SARS-CoV-2 in China, neutralization assay and magnetic particle chemiluminescence method were used to test the 117 serum samples from individuals who had recovered 4 weeks post-infection. The results indicated that the levels of NAbs against prototype and Omicron variants BA.5 were significantly higher than those against Omicron variants BQ.1, XBB.1.1, XBB.1.9, XBB.1.16 and EG.5, regardless of whether the infection was primary or secondary. Conclusions The cross-protection provided by NAbs induced by prototype and Omicron BA.5 variants was limited when challenged by BQ.1, XBB.1.1, XBB.1.9, XBB.1.16 and EG.5 variants. This indicates that we should pay more attention to the risk of multiple infection from any novel Omicron variants that may emerge in the near future.

Infection by Hepatitis E virus (HEV), as a zoonotic disease virus, is well studied in pigs in China, but few studies in pets have been performed. This study was designed to characterize the prevalence of HEV infection among pet dogs and cats in major metropolitan areas of China. We conducted a seroepidemiological survey from 2012 to 2013 in 5 developed cities, Beijing, Shanghai, Canton, Shenzhen and Macao, by enzyme-linked immunosorbent assay (ELISA). The overall HEV seroprevalence in 658 dog and 191 cat serum samples was 21.12% and 6.28%, respectively. The analysis in dogs suggested that there were significant differences among cities, and the positive rate of HEV-specific antibody in all cities ranged from 6.06% (Shenzhen) to 29.34% (Beijing). Older pet cats have a high risk (OR, 10.25) for HEV seropositivity, but no strong relationship was observed between different genders and age groups. Additionally, it was revealed that stray dogs, omnivorous pet dogs and pet cats who share food, such as kitchen residue, with the general population would have a higher risk for HEV seropositivity. The odds ratios for these groups are 2.40, 2.83 and 5.39, respectively, compared with pet dogs and cats fed on commercial food. In this study, we first report that HEV is prevalent in pet dogs and cats in several large cities in China. Swill and kitchen residue may be a potential risk for HEV transmission from human to pets. As the sample size was relatively small in this study and may not be fully representative of China, further investigation is required to confirm the conclusions.

Hepatitis E virus (HEV) infection is widespread in China, but few studies have been carried out in Guangdong Province. This study aimed to characterize the prevalence of HEV infections among swine, swine farmers and the general population in Guangdong Province. We conducted an epidemiological study that included swine, swine farmers and health examination attendees in Guangdong from 2011 to 2013. The overall seroprevalence of anti-HEV antibodies in swine was 64.7%. The results revealed that growing pigs, sows and boars (OR ranges from 3.5 to 21.5) have a higher risk than nursery pigs. HEV RNA in swine bile showed that HEV is epidemic in swine in the Pearl River Delta, with the highest prevalence of 22.73% in Foshan. Some genomes of HEV strains from each district were sequenced. Phylogenetic analysis of partial open reading frame 2 (ORF2) shows that they belong to genotype IV and are most closely related to isolates from China. In total, 307 participants were enrolled in the study, including 114 swine farmers and 193 attendees from hospitals. IgG anti-HEV was detected in 48.25% of swine farmers and in 38.34% of the general population. Seroprevalence rates were almost stratified by age, with a higher positive rate for males compared to females across all age groups. Women on swine farms appeared to have a lower risk of infection compared to the general population, revealing that the risk factors for HEV infection are not unique. The results suggested that there were other risk factors for HEV infection. HEV infection is prevalent in Guangdong, but due to the small sample sizes, more investigations are needed to assess the potential impact of HEV infection, and many additional risk factors should be considered.

Background: Serosurveillance of epidemic cerebrospinal meningitis (ECM) in healthy individuals is crucial for assessing disease risk and evaluating the effectiveness of vaccinations. However, this practical work is rare in China. Methods: We conducted cross-section serosurveillance in Guangzhou, Zhanjiang, and Heyuan in Guangdong Province, measuring Anti-Nm IgG with serogroups A, C, Y, and W, and analyzed the trends using a generalized additive model (GAM). Results: During 2019–2022, 7752 participants were included. The overall antibody positivity rate for serogroups A, C, Y, and W were 60.75%, 15.51%, 32.83%, and 14.56%, respectively. High Anti-Nm IgG was in children aged 0–5 and 5–10 years old. Geometric mean concentrations (GMCs) of Anti-Nm IgG were higher and correlated positively with vaccine doses compared with unvaccinated individuals. The GMC showed a consistent decrease trend in the vaccinated and a U-shaped curve in populations. The declined rates of GMC were 1.59 (95% CI: 1.03, 2.14) µg/mL, 1.65 (95% CI: 1.28, 2.03), 0.62 (95% CI: 0.22, 1.03), and 0.31 (95% CI: 0.08, 0.53) µg/mL per year for serogroups A, C, Y, and W, respectively. Conclusions: There were differences in antibody positivity rate and GMC for the four serogroups of ECM in the healthy individuals of Guangdong Province, with serogroup A showing the highest, and the demographic differences highlighted the high seroprevalence of Neisseria meningitidis in younger people. The variable prevalence rates among serogroups A, C, Y, and W and the observed decline in antibody titers underscore the need for adjustments in the immunization program targeting the meningococcal vaccine.

Guangdong is a hyperepidemic area of dengue, which has over 0.72 million cumulative cases within the last four decades, accounting for more than 90% of cases in China. The local epidemic of dengue in Guangdong is suspected to be triggered by imported cases and results in consequent seasonal transmission. However, the comprehensive epidemiological characteristics of dengue in Guangdong are still unclear. The epidemiology, seroprevalence, molecular evolution of dengue virus, and the development of policies and strategies on the prevention and control of dengue were analyzed in Guangdong, China from 1978 to 2017. Seasonal transmission of dengue virus in Guangdong, China was mainly sustained from July to October of each year. August to September was the highest risk period of local dengue outbreaks. Most of the dengue cases in Guangdong were young and middle-aged adults. Five hundred and three fatal cases were recorded, which declined within the last two decades ( = 10). The serological test of healthy donors' serum samples showed a positive rate of 5.77%. Dengue virus 1-4 (DENV 1-4) was detected in Guangdong from 1978 to 2017. DENV 1 was the dominant serotype of dengue outbreaks from 1978 to 2017, with an increasing tendency of DENV 2 since 2010. Local outbreaks of DENV 3 were rare. DENV 4 was only encountered in imported cases in Guangdong, China. The imported cases were the main source of outbreaks of DENV 1-2. Early detection, management of dengue cases, and precise vector control were the key strategies for local dengue prevention and control in Guangdong, China. Dengue has not become an endemic arboviral disease in Guangdong, China. Early detection, case management, and implementation of precise control strategies are key findings for preventing local dengue transmission, which may serve for countries still struggling to combat imported dengue in the west pacific areas.

Vaccination is the key to prevent varicella zoster virus (VZV) infection in children. Voluntary and self-funded strategies have led to variable vaccination rates against VZV in China. For low-income populations, in particular, the effects of VZV vaccination have been insufficiently estimated. Community-based serosurveillance was conducted in two less developed regions, Zhanjiang and Heyuan, of Guangdong, China. Anti-VZV IgG antibodies in serum were detected by ELISA. The vaccination data were derived from the Guangdong Immune Planning Information System. A total of 4221 participants were involved, of which 3377 were from three counties of Zhanjiang and the other 844 were from one county of Heyuan, Guangdong, China. The total VZV IgG seropositivity rate in vaccinated individuals was 34.30% and 42.76%, while it was 89.61% and 91.62% in non-vaccinated populations of Zhanjiang and Heyuan, respectively. The seropositivity rate increased gradually with age, reaching ~90% in the >20- to 30-year-old group. The VarV vaccination rates of children aged 1–14 years were 60.47% for one dose and 6.20% for two doses in Zhanjiang, and 52.24% for one dose and 4.48% for two doses in Heyuan. Compared with the non-vaccinated group (31.19%) and one-dose group (35.47%), the positivity rate of anti-VZV IgG antibodies was significantly higher in the two-dose group (67.86%). Before the VarV policy was reformed, the anti-VZV IgG positivity rate was 27.85% in the one-dose-vaccinated participants, which increased to 30.43% after October 2017. The high seroprevalence in participants was due to infection of VZV in Zhanjiang and Heyuan, not vaccination against VZV. Children aged 0–5 years are still vulnerable to varicella, so a two-dose vaccination program should be implemented to prevent onward transmission of VZV.

Background: Mass basic and booster immunization programs effectively contained the spread of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) virus, also known as COVID-19. However, the emerging Variants of Concern (VOCs) of COVID-19 evade the immune protection of the vaccine and increase the risk of reinfection. Methods: Serum antibodies of 384 COVID-19 cases recovered from SARS-CoV-2 infection were examined. Correlations between clinical symptoms and antibodies against VOCs were analyzed. Result: All 384 cases (aged 43, range 1–90) were from 15 cities of Guangdong, China. The specific IgA, IgG, and IgM antibodies could be detected within 4–6 weeks after infection. A broad cross-reaction between SARS-CoV-2 and Severe Acute Respiratory Syndrome Coronavirus, but not with Middle East Respiratory Syndrome Coronavirus was found. The titers of neutralization antibodies (NAbs) were significantly correlated with IgG (r = 0.667, p < 0.001), but showed poor neutralizing effects against VOCs. Age, fever, and hormone therapy were independent risk factors for NAbs titers reduction against VOCs. Conclusion: Humoral immunity antibodies from the original strain of COVID-19 showed weak neutralization effects against VOCs, and decreased neutralizing ability was associated with initial age, fever, and hormone therapy, which hindered the effects of the COVID-19 vaccine developed from the SARS-CoV-2 prototype virus.