Weekly national seasonal respiratory report
Week 34 2021

About this release

This release is a weekly report on epidemiological information on seasonal influenza activity in Scotland. Due to COVID health care services are functioning differently now compared to previous flu seasons so the consultation rates are not directly comparable to historical data.

Main points

Overall assessment:

• Influenza activity is currently at Baseline level.
• Respiratory syncytial virus (RSV) remained at Low activity level but has increased since last week.
• Rhinovirus remained at Low activity level but has increased since last week.
• Human metapneumovirus increased to Low activity level.
• While these respiratory infections are shown to be at low activity levels based on epidemiological measurement using the Moving Epidemic Method, we have observed a week on week increase in laboratory-confirmed diagnoses for RSV since week 23 2021, and a recent increase in rhinovirus and human metapneumovirus.

In week 34 (week ending 29/08/2021), provisional data showed:

• The rate of influenza-like illness (ILI) was at Baseline activity level (0.5 per 100,000 population).
• The swab positivity of influenza was at Baseline activity level (0.00%, 0/3219).
• The incidence rate of influenza was at Baseline activity level (0.00 per 100,000 population).
• There were no influenza cases this week. The low numbers of influenza may be related to SARS-CoV-2 interventions combined with the traditional low transmission of influenza during the summer months.
• The proportion of NHS24 calls that were for respiratory symptoms in week 34 increased from Baseline to Moderate activity level. NHS24 calls in the <1-year age group and 15-44 age group increased to Moderate activity level. The 1-4 years age group increased to High activity level and the 45-64 age group increased to Low activity level. All other age groups remained at Baseline activity level.
• Respiratory syncytial virus (RSV) remained at Low activity level, with 134 laboratory-confirmed cases in Scotland during week 34 (2.5 cases per 100,000 population). This compares with 103 laboratory-confirmed cases (1.9 cases per 100,000 population) in week 33.
• Rhinovirus remained at Low activity level, with 202 laboratory-confirmed cases in Scotland during week 34 (3.7 cases per 100,000 population). This compares with 146 laboratory-confirmed cases (2.7 cases per 100,000 population) in week 33.
• Human metapneumovirus (HMPV) increased to Low activity level, with 19 laboratory-confirmed cases in Scotland during week 34 (0.3 cases per 100,000 population). This compares with 9 laboratory-confirmed cases (0.2 cases per 100,000 population) in week 33. All other non-flu pathogens were at Baseline activity level.

Background

Surveillance of influenza infection is a key public health activity as it is associated with significant morbidity and mortality during the winter months, particularly in those at risk of complications of flu e.g. the elderly, those with chronic health problems and pregnant women.

The spectrum of influenza illness varies from asymptomatic illness to mild/moderate symptoms to severe complications including death. In light of the spectrum of influenza illness there is a need to have individual surveillance components which provide information on each aspect of the illness.

There is no single flu surveillance component that can describe the onset, severity and impact of influenza or the success of its control measures each season across a community.

To do so requires a number of complementary surveillance components which are either specific to influenza or its control, or which are derived from data streams providing information of utility for other PHS specialities (corporate surveillance data). Together, the influenza surveillance components provide a comprehensive and coherent picture on a timely basis throughout the flu season. Please see the influenza page on the HPS website (external website) for more details.

Further information

The next release of this publication will be 9 September 2021.