H1N1 Beijing
Description
Virological Profile of H1N1 in Beijing
The predominant H1N1 strain in Beijing is a descendant of the 2009 pandemic A(H1N1)pdm09 virus, featuring:
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Genetic composition: 8 recombined RNA segments from swine, avian, and human influenza viruses
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Surface proteins: Hemagglutinin (HA) and neuraminidase (NA) enabling host cell entry/release
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Antigenic drift: 2023 strains showed mutations at HA antigenic sites (K54Q, K136N, K283E) compared to vaccine strains, suggesting reduced vaccine efficacy
Table 1: Key Outbreak Statistics
Key trends:
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Age distribution: Highest attack rates in 5-14 year olds (31.8% in 2009)
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Transmission: R₀ estimated at 1.68 (95% CI 1.25-2.26) in school settings
Table 2: Significant Risk Modifiers511
| Protective Factors | Odds Ratio (95% CI) | Risk Factors | Odds Ratio (95% CI) |
|---|---|---|---|
| Vaccination | 0.08 (0.05-0.12) | Eye rubbing | 1.68 (1.25-2.26) |
| Classroom space >1.6m²/student | 0.17 (0.07-0.41) | Crowded transport | 1.76 (1.08-2.86) |
| Handwashing post-sneezing | 0.48 (0.36-0.65) | Sleep <7hrs/night | 1.49 (1.04-2.13) |
Mortality Burden
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2007-2013 average: 2,375 influenza-associated deaths/year (3% of total mortality)
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2009 pandemic: 23-25% mortality in severe cases requiring hospitalization
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High-risk groups: Elderly (≥65 years) showed 4.8x higher mortality vs young adults
Public Health Response Framework
Beijing's containment strategy integrates:
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Surveillance:
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Vaccination:
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Non-pharmaceutical Interventions:
Genetic Surveillance Findings (2023)
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Clade distribution:
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Antigenic drift: HA mutations (K54Q, K136N) in 83% of strains suggest vaccine mismatch
Current Status (2024-2025)
Product Specs
Q&A
What was the timeline of H1N1 detection and spread in Beijing?
The 2009 pandemic influenza A/H1N1 was first detected in Beijing in May 2009. The first confirmed case in Beijing was an 18-year-old woman who had returned from the United States . By September 15, 2009, 613 confirmed cases had been investigated in Beijing, leading to the quarantine of 7,099 close contacts . Beijing experienced a distinctive dual peak pattern of influenza epidemic during the A/H1N1 2009 pandemic, formed by the pandemic H1N1 strain followed by a subsequent influenza B epidemic in 2009/2010 . A small peak of seasonal H3N2 was also observed prior to the H1N1 pandemic peak .
What were the distinguishing clinical features of H1N1 infection in Beijing patients?
The 2009 H1N1 pandemic influenza in Beijing primarily caused upper respiratory tract infections . Cough was significantly associated with influenza A virus infection compared to other respiratory viruses (p<0.001) . China was the first country to systematically reveal the clinical features and patterns of the new H1N1 virus, establishing the world's largest clinical database of H1N1 cases . An important finding was that approximately 17.2% of individuals with confirmed pandemic H1N1 2009 infection had subclinical or asymptomatic infection , suggesting that one in six infected persons showed no symptoms.
How did the clinical presentation of H1N1 differ from other respiratory viruses circulating in Beijing?
H1N1 2009 pandemic influenza was distinguishable from other respiratory illnesses by symptom constellation. Among patients presenting with influenza-like illness (ILI) in Beijing from June 2010 to May 2011, influenza A virus (including H1N1) accounted for 22.9% of cases, while other viruses were present at frequencies less than 3.0% . The H1N1 pandemic appeared to delay the epidemic of common respiratory viruses, with the exception of human rhinovirus, suggesting possible viral interference mechanisms during transmission .
What diagnostic approaches were developed and implemented for H1N1 detection in Beijing?
China was the first country to successfully develop a new diagnostic reagent for influenza A (H1N1) virus, which was subsequently shared globally . Under the guidance of the Beijing Center for Disease Prevention and Control (Beijing CDC), a network of 55 collaborating laboratories was established to perform reverse transcription PCR testing to confirm cases of pandemic H1N1 2009 . This diagnostic network enabled rapid case detection through multiple channels, including:
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Border entry screening
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Influenza-like illness (ILI) screening in hospitals
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Health follow-up of international travelers
How were serological surveys conducted to assess H1N1 prevalence in Beijing?
Serological surveys were conducted before and after the 2010/2011 influenza season to examine the evolution of herd immunity against pandemic H1N1 2009 virus in Beijing . These surveys involved large sample sizes (4,509 and 4,543 subjects in pre- and post-season surveys, respectively) and used hemagglutination inhibition assays to detect antibodies against pandemic H1N1 . The standardized seroprevalence of pandemic H1N1 2009 influenza increased from 22.1% pre-season to 24.3% post-season, indicating a slight but statistically significant increase in population immunity .
What were the primary risk factors for H1N1 transmission identified in Beijing studies?
Beijing research identified several key risk factors for H1N1 transmission:
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Younger age - children showed higher susceptibility
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Being a household member of an index case-patient
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Exposure during the index case-patient's symptomatic phase
The research demonstrated that the basic transmission coefficient (R0) early in the pandemic was 1.3-1.5, and that medical isolation measures could effectively delay spread . The household contact risk factor was particularly significant, with attack rates exceeding 5% among household members compared to less than 1% among aircraft passengers .
How did transmission patterns of H1N1 in Beijing influence public health response strategies?
Research on transmission patterns revealed that early intervention through medical isolation could delay the spread of H1N1, which influenced China's decision not to declare a "public health emergency" . The identification of younger age and household contact as major risk factors informed targeted prevention strategies . The understanding that approximately 17.2% of infections were asymptomatic had significant implications for surveillance approaches, as traditional symptom-based screening would miss these cases .
How did seroprevalence of H1N1 antibodies vary across different age groups in Beijing?
Serological surveys revealed significant age-related differences in H1N1 antibody prevalence:
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Children aged 0-5 years showed increased geometric mean titers (GMTs) after the 2010/2011 season, likely due to natural infection
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The elderly (≥60 years) exhibited increases in both seroprevalence and GMT, attributed primarily to vaccination
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School-age children (6-15 years) maintained a high seroprevalence of 33.1%, approximately three times that of the elderly group, but showed no significant post-season increase despite vaccination campaigns
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Male subjects showed a significant post-season increase in antibody levels while females did not, suggesting potential gender differences in either infection rates or preventive behaviors
What quarantine and contact tracing methodologies were implemented in Beijing during the H1N1 pandemic?
Beijing implemented comprehensive contact tracing and quarantine measures for H1N1 cases. Each confirmed case (including both symptomatic and asymptomatic cases) triggered a detailed epidemiological investigation conducted by Beijing and local CDCs within 6 hours of confirmation . Index case-patients were immediately quarantined in designated hospitals for treatment while in isolation . All close contacts were located, quarantined, and monitored for infection development. This approach enabled researchers to calculate precise attack rates among different exposure categories and identify key risk factors for transmission .
How did Beijing's vaccination strategy evolve in response to the H1N1 pandemic?
China became the first country to successfully develop a new H1N1 vaccine . Beijing implemented a massive vaccination campaign, contributing to the nationwide vaccination of 105 million people . The vaccination strategy included free influenza vaccination campaigns targeting school children and the elderly . China established the world's largest H1N1 vaccine safety monitoring system covering 70 million people . In subsequent seasons, the pandemic H1N1 strain was incorporated into the trivalent seasonal influenza vaccine .
What molecular and structural analyses were conducted on the H1N1 virus in China?
Chinese researchers successfully analyzed the crystal structures of the neuraminidase (NA) and hemagglutinin (HA) of the H1N1 virus for the first time . These structural analyses were crucial for understanding viral binding mechanisms, antiviral drug susceptibility, and vaccine development. The research resulted in 90 SCI papers being published, with three winning first prizes for science and technology at the provincial and ministerial levels .
How were multiplex PCR assays utilized to study viral co-infections during the H1N1 pandemic in Beijing?
Research in Beijing employed multiplex or single PCR tests to simultaneously detect multiple respiratory viruses in patient samples, allowing for the study of viral co-infections and competitive dynamics . This approach revealed that the epidemic of common respiratory viruses, except human rhinovirus, was delayed during the H1N1 pandemic, suggesting potential interference between respiratory viruses . From June 2010 to May 2011, researchers tested 279 throat swabs for twelve respiratory viruses using multiplex RT-PCR, finding that one or two viruses were detected in 29% of samples, with influenza A accounting for 22.9% .
What role did traditional Chinese medicine play in H1N1 treatment in Beijing?
Major breakthroughs were made in the treatment of H1N1 influenza with traditional Chinese medicine . While specific methodologies were not detailed in the provided search results, China's approach to H1N1 treatment incorporated both Western and traditional Chinese medical practices. This integrative approach contributed to China's advanced level of H1N1 diagnosis and treatment, which was recognized as being at the most advanced level worldwide .
Product Science Overview
The H1N1 Influenza-A Virus Beijing/262/95 is a strain of the H1N1 subtype of the Influenza A virus. This particular strain was isolated in Beijing, China, in 1995. Influenza A viruses are known for their ability to cause significant respiratory illnesses in humans and animals, and the H1N1 subtype has been responsible for several pandemics throughout history.
The H1N1 influenza virus has a long history, dating back to the 1918 Spanish flu pandemic, which caused millions of deaths worldwide . Over the years, the H1N1 virus has undergone numerous genetic changes, leading to the emergence of various strains. The Beijing/262/95 strain is one of these variants, which has been studied for its unique genetic and antigenic properties .
The H1N1 Influenza-A Virus Beijing/262/95 belongs to the delta-like clade of the swine H1 lineage . Genetic analyses have shown that this strain has distinct genetic markers that differentiate it from other H1N1 strains. The hemagglutinin (HA) protein, which is responsible for the virus’s ability to bind to host cells, has been a focal point of research. The HA protein of the Beijing/262/95 strain has been expressed in various host systems for study and reagent production .
Since its isolation in 1995, the Beijing/262/95 strain has remained geographically restricted to Asia . This limited distribution contrasts with other H1N1 strains, which have spread globally. The reasons for this geographic restriction are not entirely understood but may be related to specific genetic and antigenic properties of the strain.
The H1N1 Influenza-A Virus Beijing/262/95 has been the subject of various research studies aimed at understanding its genetic makeup and potential impact on public health. Researchers have used this strain to study mutation accumulation and the evolutionary dynamics of the H1N1 virus . These studies have provided valuable insights into the mechanisms of viral evolution and the factors that influence the emergence and spread of new influenza strains.
