Research and analysis

Influenza A (H1N1pdm09): infectious and incubation period, and pre-symptomatic and asymptomatic transmission

A rapid evidence summary identifying and summarising evidence related to the infectious and incubation period, and pre-symptomatic and asymptomatic transmission of Influenza A (H1N1pdm09).

• From: UK Health Security Agency
• Published: 8 May 2025
• Last updated: 3 December 2025 — See all updates

Documents

Infectious and incubation period, and pre-symptomatic and asymptomatic transmission of influenza A H1N1pdm09 subtype: a rapid evidence summary

Ref: GOV-18309

PDF, 639 KB, 50 pages

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Details

This rapid evidence summary summarised available evidence on the infectious (timeframe in which an individual may transmit the infection to others) and incubation period (time between contracting an infection and symptom onset) as well as evidence on pre-symptomatic and asymptomatic transmission and location of exposure of influenza A subtype H1N1pdm09 (search between 1 January 2009 to 31 July 2024).

Twenty-six studies were included, 4 cross-sectional, 18 prospective and 4 retrospective cohort studies.

Published 8 May 2025

Last updated 3 December 2025 + show all updates

1. 3 December 2025

   Updated the title to be more specific, and made a few minor updates to the wording of the details (for example, 'review' changes to 'summary').

2. 8 May 2025

   First published.