december 2022

GIHSN SevScale: developing a severity scale for influenza cases reported to the Global Influenza Hospital Surveillance Network

Duration: Dec 2022 - Dec 2023


The Global Influenza Hospital Surveillance Network (GIHSN) has existed since 2012 and its objectives have evolved over time, with a new focus established since the 2019/20 season. The focus aims to determine very detailed sequence data (Whole Genome Sequence data) from specimens collected from hospitalized influenza positive patients. These results are uploaded to GISAID and the objective is to integrate this data collected into the bi-annual WHO vaccine selection procedure which is led by WHO and involves the WHO Collaborating Centres, the National Influenza Centres and other key stakeholders.
The GIHSN sequence data is considered to represent severe patients as they concern hospitalized patients. However, there is currently no system to assess the severity of hospitalized patients in GIHSN.
Having this additional information would allow the WHO Collaborating Centres (and other research groups working with the GISAID database) to identify the more severe cases of influenza and take case severity into account when deciding which strains should be included in the influenza vaccine.


Retrospective analysis of the GIHSN database which uses advanced statistical methods to establish an age specific Severity Scale for the influenza-positive hospitalized patients collected in the GIHSN project

Project design

Phase 1: feasibility assessment

  • exploratory analysis of the dataset
  • preliminary Item Response Models to distinguish items that define severity and the contribution of each item to severity
  • expert group meetings to provide advice and direction, supporting the analysis and to provide clinical expertise

Phase 2: data analysis, validation and communication of the results

Countries included in the analysis:

We aim to include data from a geographically and economically diverse group of countries in the development of the severity scale. The countries included in the project are Spain, Canada, Russia, Türkiye, Brazil, South Africa, Kenya, India and Côte d’Ivoire.

General focus of the research

The focus of the GIHSN SevScale is to develop a severity scale that is a) age-specific and b) based on pathogen / infection ilness factors only. It will therefore be primarily used for surveillance and research purposes only. The GIHSN SevScale will not develop a severity scale for the clinical management of patients as these scales already exist.>

Summary of the impact

  1. Creation of a new tool to define the severity of influenza in hospitalized patients that can be applied to all patients in the GIHSN network
  2. The GIHSN SevScale can be uploaded to GISAID so that researchers have extra information on the severity of the sequence data in GISAID
  3. The GIHSN SevScale will have the potential to be used by other researchers around the world who collect hospitalized data on influenza positive patients and upload sequence data or want to categorize their patients in a systematic manner

Communication of the results

The results of the project will be presented at the GIHSN Annual Meeting, at a scientific conference and as a scientific publication.

Dit project wordt gesubsidieerd door
Foundation for Influenza Epidemiology - Fondation de France, Paris, France
Global Influenza Hospital Surveillance Network (GIHSN)