Influenza Surveillance       

Click here to go to charts

In Malta, sentinel surveillance of Influenza activity in the community has been underway since 2003.  The main objectives of a sentinel surveillance system are to:

• estimate the proportion  of primary health encounters with Influenza

• describe aspects of the epidemiology of  Influenza at GP level

• obtain data which contributes to Influenza prevention and control by identifying trends

• obtain information on circulating viral strains of Influenza

Sentinel surveillance study involves a number of voluntary general practitioners who report on Influenza activity in their practice including Influenza like-illness (ILI) and acute respiratory infection (ARI).

A case of Influenza-like illness is defined as a person presenting to the general practitioner with sudden onset of symptoms and at least one of the following symptoms: fever or feverish, malaise, headache,  myalgia and at least one of the following three respiratory symptoms: cough, sore throat and shortness of breath.

Acute respiratory infection is defined as as a person presenting to the general practitioner with sudden onset of symptoms and at least one of the following four symptoms: cough, sore throat, shortness of breath and coryza.  The definition comprises common cold but not rhinitis and sinusitis.

 A number of problems are encountered in trying to perform sentinel surveillance at community level in Malta since:

• Patients are not registered to a particular GP and can therefore go to different GPs  in private or public practice

• Most GPs  do not have existing registers of their patients list so their patient population is not known.  To overcome this problem, an idea of the burden of illness can be obtained from the proportion of Influenza cases seen out of the total number of the primary health encounters.  In fact each participating GP reported on the total number of health encounters seen at his practice for any reason during each reporting week.  This was used as the denominator in estimating the proportion of Influenza cases over the total number of the primary health encounters.

Participating GPs were provided with specific forms to report on Influenza cases.  Information on cases includes age, gender, vaccination status and requests for virological testing.  Each of the GPs also gave details of age and gender of patients seen at their practice over the same period for any condition in order to describe the primary health encounters in their practice. Throat or nasal swabs are taken by the GP which are then sent to the Virology Department at St. Lukes Hospital where they are analysed for Influenza A and B viruses.

The proportion of Influenza Like Illness of the primary health encounters  is calculated using the number of reported  cases (in accordance with the specified case definition) as the numerator, while the total number of health encounters of participating GPs during the study period was used as the denominator.

Figures below shows the number of primary health encounters with Influenza Like Illness and Acute Respiratory Infection per 1000 primary health encounters during the Influenza season from October 2007 (Week 40) till date.  This is updated on a weekly basis in accordance with data received by the Infectious Disease Prevention and Control Unit.

Downloads - Week 17

Influenza Like Illness Chart - download

Acute Respiratory Infection Chart - download

Other Charts

Influenza Like Illness vs Rate of Respiratory admissions - download