China’s arbovirus landscape in 2026: immunity, outbreaks and vaccine lessons

Arboviruses remain one of the most persistent public health challenges facing China, and a new open-access review published in Discover Viruses on 12 October 2026 argues that the country’s situation has shifted markedly in recent years. The review, written by Yiu-Wing Kam, Shan Wu and Jiachen Wu, synthesizes evidence on human immune responses, pathogenesis and vaccine development for four clinically significant mosquito-borne viruses: dengue virus (DENV), Zika virus (ZIKV), Japanese encephalitis virus (JEV) and chikungunya virus (CHIKV). Drawing on literature from 2010 to 2026, the authors identify immune correlates of protection and disease enhancement, evaluate vaccine candidates, and set out research priorities for the years ahead.

The epidemiological picture the authors describe is one of accelerating change. Dengue virus remains endemic in more than 100 countries, with annual cases now estimated between 50 and 100 million worldwide, a dramatic rise from the 0.4 to 1.3 million annual cases documented between 1996 and 2005. In 2026 alone, the Americas reported over 3 million dengue cases as of epidemiological week 18, with Brazil bearing the highest burden. China, once considered a low-risk region, has experienced increasing autochthonous transmission events, particularly in its southern provinces. Guangdong and Yunnan remain hotspots, and 2026 saw seasonal activity begin in April, two months earlier than historical averages, likely driven by above-average temperatures and expanded Aedes habitats.

Chikungunya has become a particular concern. In 2025, China recorded its largest chikungunya outbreak ever, centered in Guangdong Province with more than 2,500 locally acquired cases, an incidence of approximately 4.5 per 100,000 population based on the province’s roughly 126 million residents. The outbreak was concentrated in Guangdong with approximately 2,100 cases, alongside smaller clusters in Fujian and Guangxi. Globally, 2025 brought a resurgence of more than 445,000 cases and 155 deaths across 40 countries, with Cuba reporting over 50,000 cases. The circulating Chinese strain carried adaptive mutations including E2-L210Q and E2-I211T, in addition to the well-characterized E1-A226V mutation that enhances replication in Aedes albopictus and has historically facilitated transmission into temperate regions.

The virology underlying these threats differs sharply between virus groups. DENV, ZIKV and JEV are closely related flaviviruses with genomes of roughly 11,000 nucleotides encoding three structural and seven non-structural proteins, yet they differ profoundly in serotype structure. DENV exists as four distinct serotypes with more than 40 percent nucleotide sequence variation, which is clinically critical because infection with one serotype does not confer lasting cross-protection and can instead prime antibody-dependent enhancement (ADE) upon secondary infection. JEV, by contrast, comprises five genotypes within a single serotype, so vaccines derived from one genotype, such as the GIII-based SA14-14-2, remain broadly effective. ZIKV occupies an intermediate position with three lineages that are not separate serotypes; its Asian lineage, responsible for the 2015 to 2017 outbreaks, shows greater pathogenicity than African lineages despite slower replication kinetics, a paradox the authors attribute to immune modulation and tissue tropism rather than replication speed alone.

Within China, DENV-1 and DENV-2 are the predominant serotypes, accounting for approximately 90 percent of cases. Regional distribution varies: Guangdong predominantly experiences DENV-1 and DENV-2, while Yunnan has a higher proportion of DENV-3, roughly 15 to 20 percent of cases, and Fujian shows a mixed distribution with DENV-2 slightly more common. Serotype shifts are associated mainly with importation events from Southeast Asia rather than intrinsic seasonal patterns. In southern China, adult DENV seroprevalence ranges from 30 to 60 percent, varying by age, geography and prior outbreak history, a heterogeneity with direct implications for ADE risk and vaccine deployment. Notably, no fifth DENV serotype has been officially recognized as of 2026, despite proposed strains from Malaysia and Singapore, because serotype classification requires distinct neutralization profiles rather than genetic distance alone.

The immunology of protection and pathology is central to the review. Type I interferons constitute the first line of defense, but each virus has evolved antagonism mechanisms: DENV NS5 degrades STAT2 via UBR4 recruitment, ZIKV NS5 promotes STAT2 degradation through a distinct mechanism, JEV NS5 inhibits JAK-STAT signaling, and CHIKV nsP2 interferes with STAT1 phosphorylation through its protease domain. Neutralizing antibodies target the envelope protein in flaviviruses and the E2 glycoprotein in alphaviruses; for CHIKV, the linear epitope E2EP3 elicits potent neutralizing antibodies that protect in animal models. On the pathogenic side, ADE occurs when sub-neutralizing antibody concentrations enhance viral entry into Fcγ receptor-bearing cells, a phenomenon well documented for secondary dengue infections and demonstrated in vitro between DENV and ZIKV, though the clinical significance of the latter remains debated. Original antigenic sin, in which memory B and T cells from a primary infection respond suboptimally to a heterotypic secondary serotype, may also worsen outcomes, although its role in severe dengue remains controversial, and cross-reactive immunity can be protective, conferring short-term cross-protection of less than three months.

Clinical features further distinguish these pathogens. For DENV, fever typically lasts three to seven days, with a critical phase following defervescence in which severe dengue may develop; interleukin-6 and CD8+ T cell responses contribute to increased vascular permeability. ZIKV infection can produce Guillain-Barré syndrome persisting weeks to months, with rash appearing in 70 to 80 percent of symptomatic patients. JEV causes seizures in 50 to 70 percent of encephalitic cases, particularly in children, and neurological sequelae persist in 30 to 50 percent of survivors. CHIKV acute fever lasts five to seven days, but arthralgia can persist far longer: one study reported persistent arthralgia in 13.3 percent of patients at six months, while other longitudinal studies have documented chronic symptoms in 40 to 60 percent of patients at 12 to 24 months, depending on age, sex and initial severity.

The vaccine landscape is uneven. On the chikungunya front, the FDA approved Ixchiq (VLA1553), a live-attenuated vaccine with a 60-amino acid deletion in nsP3 that prevents replication in mosquito vectors, on 9 November 2023. In Phase 3 trials, more than 96 percent of subjects developed neutralizing antibodies persisting for at least 180 days, and passive transfer of human vaccine sera protected cynomolgus macaques completely against viremia. Limitations include restriction to people aged 18 and older and severe chikungunya-like adverse reactions in approximately 1.5 percent of recipients. China’s National Medical Products Administration has been evaluating Ixchiq since late 2025, but formal approval had not been granted as of May 2026. For dengue, Dengvaxia is restricted to seropositive individuals because of ADE risk, while Qdenga (TAK-003) demonstrated 80.2 percent efficacy against virologically confirmed dengue and 90.4 percent against hospitalized dengue in the Phase 3 TIDES trial, with efficacy varying by baseline serostatus. Butantan-DV showed 79.6 percent overall efficacy in a Brazilian Phase 3 trial. No domestically developed DENV vaccine is licensed in China, although several candidates are in preclinical and early clinical stages, including a Phase 1 trial of a Chinese inactivated vaccine completed in 2024. No licensed ZIKV vaccine exists anywhere as of 2026.

Against this backdrop, China’s JEV program stands out as a model. The SA14-14-2 live-attenuated vaccine, developed in China and used nationally since 1988, was incorporated into the Expanded Program on Immunization in 2008 and helped reduce JEV incidence from approximately 5,000 annual cases in 2000 to fewer than 500 in 2024, with coverage reaching 95 percent nationally and over 98 percent in eastern provinces. Recent studies from 2024 to 2025 confirmed that the vaccine continues to induce broadly neutralizing antibodies against the emerging GI genotype, with clinical effectiveness above 95 percent where GI dominates. The review’s authors argue that the lessons of this program, including strong government commitment, EPI integration and adaptation to local epidemiology, should inform strategies against other arboviruses, alongside vector control measures such as Wolbachia deployment, which has been piloted in Guangzhou and Shenzhen and has reduced dengue incidence by 50 to 80 percent in deployment areas in Singapore, Malaysia and Brazil.

Looking forward, the authors emphasize that climate change represents the most significant long-term threat. Modeling using CMIP6 ensemble models under moderate and high-emission scenarios indicates that by 2050, suitable habitat for Aedes albopictus will expand northward into previously low-risk provinces including Henan, Shandong, Hebei and the Beijing-Tianjin area. The DENV transmission season is projected to lengthen by 20 to 40 days in southern provinces, and annual DENV cases could increase three- to five-fold under high-emission scenarios, with transmission risk projections rising 30 to 50 percent and model uncertainty ranging from 22 to 67 percent across ensemble members. The review identifies seven research priorities for 2026 to 2030, including tetravalent DENV vaccine development, climate-adapted surveillance, multiplex point-of-care diagnostics, molecular characterization of protective versus enhancing antibodies, cost-effectiveness analyses, novel vector control approaches and One Health surveillance integrating human, animal and environmental data, noting that the total annual economic burden of arboviruses in China is estimated at 2.3 billion yuan, roughly 320 million US dollars.

Subject of Research: Immune responses and vaccine development against mosquito-borne arboviruses in China

Article Title: Protective responses and implications for vaccine designs against arboviruses in China: a 2026 perspective

Article References: Kam, Y.-W., Wu, S., & Wu, J. (2026). Protective responses and implications for vaccine designs against arboviruses in China: a 2026 perspective. Discover Viruses, 3(1), Article 24. https://doi.org/10.1007/s44370-026-00060-1

Image Credits: AI Generated

DOI: 10.1007/s44370-026-00060-1

Keywords: arboviruses, dengue, Zika, Japanese encephalitis, chikungunya, vaccine development, antibody-dependent enhancement, China, Aedes albopictus, climate change, Wolbachia, SA14-14-2