Epidemiological Analysis of Norovirus and Rotavirus Activity in England

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This comprehensive report provides an in-depth analysis of the norovirus and rotavirus activity in England during the two-week period from November 6 to November 19, 2023. The data presented covers enteric virus (EV) outbreaks and laboratory reports, offering insights into the epidemiological landscape up to reporting week 46 of the 2023/2024 season. Key findings are based on a comparison with the 5-season average, encompassing data from 2015/2016 to 2022/2023.

Overview of Key Messages

  • Norovirus Laboratory Reports:
    • Since week 44 of the 2023/2024 season, norovirus laboratory reports have exhibited an increasing trend.
    • Weeks 45 and 46 saw a 20% reduction in the total number of norovirus laboratory reports compared to the 5-season average for the same period.
  • Rotavirus Activity:
    • Rotavirus activity during weeks 45 and 46 was 19% lower than the 5-season average.
  • Enteric Virus (EV) Outbreaks:
    • Overall, reported EV outbreaks have been on the rise since week 43.
    • However, during weeks 45 and 46, the total number of EV outbreaks remained lower than the 5-season average for the same 2-week period.
  • Norovirus Outbreaks in Hospitals:
    • Recent weeks witnessed a lower number of norovirus outbreaks reported to the Hospital Norovirus Outbreak Reporting System (HNORS) compared to the 5-season average.

Background and Context

  • Surveillance Systems:
    • The report utilizes data from four surveillance systems to comprehensively capture norovirus and rotavirus activity.
    • Surveillance is season-based to align with the winter peak of activity.
  • Norovirus Transmission Dynamics:
    • Norovirus transmission is primarily through contact with infected individuals, contaminated food, or surfaces.
    • Peak infection occurs in colder months, with winter being the most prevalent season.
  • Impact of COVID-19:
    • Since the 2019/2020 season, norovirus activity in England has shown variability, likely influenced by the COVID-19 pandemic.
    • A reduction in reporting was observed during the 2019/2020 and 2020/2021 seasons, with unusual activity in the 2021/2022 season.
    • Norovirus activity returned to pre-pandemic levels in the 2022/2023 season, peaking in early 2023 at double the pre-pandemic levels.
  • Rotavirus Vaccination Impact:
    • Introduction of the rotavirus vaccine in July 2013 led to a significant decrease in laboratory-confirmed rotavirus infections.
    • The first season post-vaccine saw a 77% decrease in infections in infants.
  • Molecular Surveillance for Norovirus:
    • The UK Health Security Agency (UKHSA) conducts norovirus characterization for strain monitoring.
    • Molecular surveillance is crucial for detecting novel strains or strain replacements, as seen historically.

Laboratory Surveillance (Up to Week 46, 2023/2024 Season)

  • Norovirus Laboratory Reports:
    • Cumulative positive norovirus laboratory reports (1,520) were 9% higher than the 5-season average.
    • Activity increased from week 44, with reports in weeks 45 and 46 being 20% lower than the 5-season average.
  • Rotavirus Laboratory Reports:
    • Cumulative positive rotavirus laboratory reports (857) were 25% higher than the 5-season average.

Outbreak Surveillance (Up to Week 46, 2023/2024 Season)

  • EV Gastroenteritis Outbreaks:
    • Cumulative EV gastroenteritis outbreaks reported to HPZone were 34% lower than the 5-season average.
    • Weeks 45 and 46 showed a 45% reduction in reported EV outbreaks compared to the 5-season average.
  • EV Outbreaks in Care Homes:
    • During weeks 45 and 46, 66% of reported EV outbreaks (norovirus) occurred in care home settings.
    • The number of outbreaks in care homes increased by 45% during this period.
  • HNORS Reports:
    • Up to week 46, 22 outbreaks were reported to HNORS, 69% lower than the 5-season average.
    • Overall, 87% of these outbreaks were laboratory confirmed as norovirus.

Molecular Surveillance Overview

  • Data Source and Interpretation:
    • The molecular surveillance data is sourced from UKHSA’s EVU.
    • Reference is made to the data sources and reporting caveats for a comprehensive understanding and accurate interpretation of trends.
  • Stability of Figures:
    • It is emphasized that the figures presented in this report have not changed since the last update, signifying a lack of additional molecular surveillance data.

Genotypic Distribution During the 2023/2024 Season

  • Total Norovirus Positive Samples:
    • As of the current season, a total of 204 norovirus positive samples have undergone molecular characterization.
  • Genogroup Distribution:
    • 64% (130 out of 204) of the characterized samples belong to genogroup 2 (GII).
    • 35% (72 out of 204) are attributed to genogroup 1 (GI).
    • 1% (2 out of 204) represent mixed genogroups.
  • Most Frequent Norovirus GII Genotypes:
    • GII.4 accounts for the highest proportion at 19%.
    • GII.3 follows closely at 16%.
  • Most Frequent Norovirus GI Genotypes:
    • GI.3 is the predominant genotype at 16%.
    • GI.6 follows with a representation of 10%.
  • GII.4 Norovirus Strain:
    • The most commonly identified GII.4 norovirus strain this season is Norovirus/GII.4/Sydney/2012-like variants.

Interpretation and Cautionary Note

  1. Data Interpretation:
    • Due to the low numbers of samples submitted for molecular surveillance in the early part of the season, caution is advised in interpreting the data.
  2. Cautionary Note:
    • The cautionary note underscores the importance of considering the context of low sample submissions, highlighting the need for prudence in drawing conclusions from the data.

Conclusion

In summary, the molecular surveillance data for norovirus during the 2023/2024 season provides valuable insights into the genotypic distribution and prevalent strains. The stability of the figures and cautionary notes emphasize the need for careful interpretation, considering the context of low sample submissions in the early part of the season. Continued molecular surveillance remains essential for understanding the dynamics of circulating norovirus variants and informing public health strategies.


TABLE 1 – Rotavirus: An Overview

Structure and Classification

Rotavirus belongs to the Reoviridae family and is a double-stranded RNA virus with a distinctive wheel-like appearance under an electron microscope. The virus is classified into multiple serogroups, with the G and P types determining the strain specificity. The G-type corresponds to the glycoprotein VP7, while the P-type corresponds to the protease-sensitive protein VP4.

Mode of Transmission

Rotavirus spreads primarily through the fecal-oral route, with transmission occurring via contaminated hands, objects, or surfaces. Ingestion of contaminated food or water also contributes to the rapid spread of the virus. Rotavirus is highly contagious, and individuals shedding the virus can be asymptomatic or exhibit mild symptoms, making it challenging to control its transmission.

II. Clinical Manifestations

Symptoms and Incubation Period

Rotavirus infections often manifest with gastroenteritis symptoms, including watery diarrhea, vomiting, fever, and abdominal pain. The incubation period ranges from 1 to 3 days, after which symptoms become evident. The severity of the disease varies, with infants and young children being the most vulnerable population.

Complications

While most cases of rotavirus infection resolve without complications, severe cases can lead to dehydration, electrolyte imbalances, and even death. Dehydration is a critical concern, particularly in resource-limited settings, and prompt medical intervention is crucial to prevent life-threatening complications.

III. Global Impact

Burden of Disease

Rotavirus is a leading cause of severe diarrhea in infants and young children globally. The World Health Organization (WHO) estimates that before the introduction of rotavirus vaccines, the virus was responsible for over 200,000 deaths annually, with the majority occurring in low-income countries.

Socioeconomic Implications

The impact of rotavirus extends beyond health outcomes, affecting economies due to healthcare costs, reduced productivity, and the burden on healthcare systems. Families often face financial strain due to medical expenses and time off work to care for sick children.

IV. Prevention and Control

Vaccination

Rotavirus vaccines have proven highly effective in preventing severe rotavirus infections. Several vaccines, such as RotaTeq and Rotarix, have been developed and incorporated into routine childhood immunization programs in many countries. The introduction of these vaccines has led to a substantial reduction in rotavirus-associated morbidity and mortality.

Hygiene and Sanitation

Promoting proper hygiene practices, including regular handwashing and safe food and water handling, is crucial in preventing rotavirus transmission. Access to clean water and sanitation facilities plays a pivotal role in reducing the prevalence of the virus, especially in resource-limited settings.

Public Health Measures

Public health initiatives aimed at increasing awareness, enhancing surveillance, and improving healthcare infrastructure contribute to the overall control of rotavirus. Early diagnosis, supportive care, and timely treatment are vital components of managing rotavirus infections and preventing complications.


TABLE 2 – Molecular Biology of Rotavirus

Structure

Rotavirus is a member of the Reoviridae family, possessing a unique, complex structure. Under an electron microscope, the virus reveals a distinct wheel-like appearance, owing to its triple-layered capsid. The outer capsid is primarily composed of two structural proteins: VP7 (glycoprotein, determining G-type) and VP4 (protease-sensitive protein, determining P-type). This genetic diversity is the basis for the classification of rotavirus strains.

Replication Cycle

The replication cycle of rotavirus is a well-orchestrated dance between the virus and host cells. After entering the host cell, the virus undergoes transcription and translation, resulting in the synthesis of viral proteins. Viral RNA replication takes place in viroplasms, specialized structures within infected cells. The assembly of new viral particles concludes the cycle, often causing cell lysis.

III. Mode of Transmission

Rotavirus spreads through the fecal-oral route, a robust strategy that enables its survival and transmission in various environments. Contaminated hands, surfaces, and objects facilitate transmission, making hygiene practices pivotal in controlling its spread. Ingestion of contaminated food and water amplifies the risk, highlighting the importance of water sanitation and food safety measures.

IV. Clinical Manifestations

Symptoms

The clinical presentation of rotavirus infection is marked by gastroenteritis, with symptoms ranging from mild to severe. Watery diarrhea, vomiting, fever, and abdominal pain are hallmark signs. The severity of symptoms often correlates with the age of the affected individual, with infants and young children at the highest risk of developing severe disease.

Complications

While most rotavirus infections resolve without complications, severe cases can lead to dehydration, electrolyte imbalances, and malnutrition. Dehydration is a critical concern, necessitating prompt intervention to prevent life-threatening complications. In resource-limited settings, where access to healthcare may be challenging, the impact of severe rotavirus infections is particularly pronounced.

V. Global Impact

Burden of Disease

Rotavirus exerts a substantial global burden, especially in developing countries. Before the widespread introduction of rotavirus vaccines, the World Health Organization (WHO) estimated over 200,000 deaths annually, with the majority occurring in regions with limited access to healthcare resources. The economic toll, both in terms of healthcare costs and societal impact, is significant.

Socioeconomic Implications

Beyond the direct health consequences, rotavirus infections place a considerable strain on economies. Families often face financial challenges due to medical expenses, loss of income during caregiving, and decreased productivity. The socioeconomic implications underscore the importance of comprehensive preventive measures.

VI. Prevention and Control Strategies

Vaccination

The development and integration of rotavirus vaccines, such as RotaTeq and Rotarix, represent significant milestones in the battle against rotavirus. These vaccines, administered as part of routine childhood immunization, have demonstrated remarkable efficacy in preventing severe rotavirus infections. Their introduction has led to a substantial reduction in morbidity and mortality associated with the virus.

Hygiene and Sanitation

Promoting proper hygiene practices is a fundamental pillar in preventing rotavirus transmission. Regular handwashing, safe food preparation, and ensuring access to clean water contribute to breaking the fecal-oral transmission cycle. In resource-limited settings, where sanitation infrastructure may be lacking, targeted interventions become even more crucial.

Public Health Measures

Public health initiatives play a pivotal role in controlling rotavirus. Increased awareness, improved surveillance, and strengthened healthcare infrastructure enhance the ability to detect and manage rotavirus cases effectively. Early diagnosis and appropriate medical care are essential in minimizing the impact of rotavirus infections.

VII. Conclusion

In conclusion, rotavirus, with its intricate molecular biology, intricate transmission dynamics, and global impact, remains a significant public health challenge. The advent of vaccines has revolutionized the landscape, offering a powerful tool in the fight against rotavirus. However, the comprehensive approach to prevention, encompassing hygiene practices, sanitation, and robust public health measures, is essential for further reducing the global burden of rotavirus and ensuring the well-being of vulnerable populations, particularly infants and young children. As research continues to unravel the nuances of rotavirus, ongoing commitment to preventive strategies remains critical in securing a healthier future for communities worldwide.


reference linjk : https://www.gov.uk/government/statistics/national-norovirus-and-rotavirus-surveillance-reports-2023-to-2024-season/national-norovirus-and-rotavirus-report-week-48-report-data-up-to-week-46-12-november-2023

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