Hospitals in China and beyond are grappling with a fast-escalating wave of A(H3N2) influenza, a strain now dominant across three major countries and testing the resilience of health systems already stretched by years of pandemic disruption. Since late November 2024, infection rates in China have climbed sharply, driving a 500% jump in antiviral medicine purchases on the Alibaba Health platform and triggering long queues at pediatric hospitals in Beijing and other major cities. At the same time, the same strain—nicknamed “superflu” in UK media—has become the leading influenza virus in Russia and England, raising concerns about sustained global circulation through the winter.
Regional spread and “superflu” dominance
A(H3N2) now dominates influenza activity in China, Russia, and England, leaving hundreds of millions of people exposed to continued transmission. In Russia, authorities have reported more than 23,400 influenza cases, with just over 80% attributed to A(H3N2) and overall flu numbers up by about 20%. England’s UK Health Security Agency (UKHSA) reports that A(H3N2) is currently the main strain circulating nationally, contributing to early-winter hospital admissions that are high for December but still below peaks seen in the 2022–23 season. In China, elevated transmission has been documented across at least 17 provinces, with particularly heavy impacts in Beijing, Tianjin, Hebei, Henan, Guangdong, Fujian, Shandong, and Shanxi. Russian surveillance data show that A(H3N2) is the only respiratory virus on an upward trajectory, while other monitored pathogens are stable or declining. This pattern, combined with rising cases in England and widespread circulation in China, suggests a regional cluster of activity with clear potential for wider international spread.
Virus evolution and vaccine timing
The current A(H3N2) surge is driven by a recently emerged viral offshoot, subclade K, nested within clade 3C.2a1b.2a.2a.3a.1. Genetic analyses from Jiaxing, China, show that local influenza epidemics between 2019 and 2024 produced six distinct peaks, with viruses in 2024 shifting into this new clade. This reflects ongoing antigenic drift, particularly in the hemagglutinin (HA) gene regions that are key targets of the immune response. The virus has circulated globally since 1968, but its continual evolution complicates efforts to match vaccines to currently circulating strains. The Jiaxing study indicates that 2023–24 seasonal vaccines still provided an estimated 29–54% protection against local A(H3N2) variants, a meaningful but imperfect shield in the face of rapid genetic shifts. Because vaccine formulations are selected months in advance based on World Health Organization recommendations, any late-breaking changes in circulating strains can reduce the degree of match, leaving populations more vulnerable when new subclades emerge.
Strained hospitals and low immunity
China’s Center for Disease Control and Prevention describes the current period as one of “rapid increase” in flu infections, with a comparatively low national vaccination rate magnifying the impact. Children’s hospitals in Beijing and other large cities have reported heavy crowding and extended waiting times, particularly among pediatric patients. Across at least 17 provinces, health facilities are operating under significant pressure as pediatric flu cases surge. Concurrently, some hospitals in Tianjin and Hebei are managing both influenza and ongoing COVID-19 cases, intensifying workload and resource demands.
Russia is facing a similar dual burden. While flu cases have climbed, COVID-19 infections have also risen by 13.7%, to around 11,000 cases, creating a combined respiratory challenge for hospitals and clinics. Although Russia has vaccinated 78.3 million people against influenza—about 53.2% of its population—roughly 69 million residents remain unvaccinated and susceptible. In England, daily hospitalizations related to respiratory illness stand at around 2,660—high for early December but still below the 5,441 daily peak recorded in the 2022–23 flu season. Experts note that these figures must be interpreted in the context of an “immunity gap”: three years of reduced seasonal influenza circulation during strict COVID-19 measures left many people, particularly children aged 5–14, with limited exposure and thus lower baseline immunity.
Surveillance, expert warnings, and mitigation
Health agencies in all three countries have intensified surveillance. China’s CDC is tracking the spread of clade 3C.2a1b.2a.2a.3a.1 and monitoring changes in the virus’s genetic makeup. Russia’s Rospotrebnadzor is mapping the outbreak across regions including the Far East, Siberia, the Urals, and the Northwest, and reports that A(H3N2) remains the only respiratory pathogen consistently rising. In England, UKHSA issues weekly flu and respiratory surveillance updates, underscoring the predominance of A(H3N2) and recommending seasonal vaccination as a primary protective measure.
Medical experts emphasize both the risks of viral evolution and the continued value of vaccines. Dr. Giuseppe Aragona notes that A(H3N2) “changes regularly,” meaning the version circulating in any given year can differ from prior strains and from the one used in seasonal vaccine formulations, potentially making people more susceptible. At the same time, studies from Jiaxing and other settings show that even partially matched vaccines can significantly reduce the risk of severe illness and hospitalization. Governments in China and Russia are urging wider vaccination uptake, especially among unvaccinated and high-risk groups, while also promoting hand hygiene, mask use in crowded settings, and rapid use of antivirals for those at higher risk of complications. In China, health authorities and pharmaceutical suppliers have moved to bolster antiviral stocks after the 500% spike in demand recorded between November 10 and 21, 2024.
Outlook for the winter season
The spread of A(H3N2) subclade K from China to Russia and the UK, supported by phylogenetic overlap between strains found in China, the UK, and France, illustrates how travel and human movement can quickly globalize an emerging seasonal threat. With large, partly immune populations in China, significant unvaccinated groups in Russia, and an immunity gap in the UK, epidemiologists expect A(H3N2) to continue circulating through the northern winter and possibly into 2025. While no national emergency declarations had been issued as of December 2024, officials in all three countries describe the situation as one requiring close monitoring and flexible responses. The current wave underscores the need for agile surveillance systems, timely vaccine updates, and sustained public health messaging. How the season unfolds will depend on the interplay between viral evolution, population immunity, and the capacity of health systems to absorb continued pressure without compromising care.
Sources:
H3N2 Outbreak in China: 95% Strain Dominance Across 17 Provinces.” Straits Times Asia, December 4, 2025.
“China Faces Huge Surge in H3N2 Flu Cases.” Macao News, December 7, 2025.
“UK Hospitals Facing ‘Worst Case Scenario’ From Super Flu.” Reuters Health, December 11, 2025.
“NHS Facing ‘Worst Case Scenario’ December Amid ‘Super Flu’ Surge.” Sky News, December 11, 2025.
“Russia is Facing a New Enemy Among Its Own Troops.” Dagens, November 29, 2025.
“Catastrophic Flu Outbreak Reportedly Cripples Russian Troops on Kherson Front.” United24media, November 24, 2025.