Surveillance of communicable diseases
One of the most important tasks of the Public Health Agency of Sweden is to continuously follow the epidemiological situation concerning communicable diseases, especially those included in the Communicable Diseases Act.
The notifiable diseases must be reported in accordance with Swedish law. A report is filed by the laboratories and the medical doctor treating the patient or performing the autopsy to the region's County Medical Officer and to the Public Health Agency of Sweden via an electronic system called SmiNet.
Other forms of surveillance
The Public Health Agency of Sweden conducts several other forms of surveillance, in addition to analysing the reported cases of notifiable diseases.
Voluntary laboratory reporting
Certain infections are very significant but are not covered by the Communicable Diseases Act. These are instead surveyed via voluntary laboratory reporting. This reporting supplements the reports received in accordance with the law. Within the framework of voluntary laboratory reporting, laboratories currently report laboratory confirmed cases of caliciviruses, clostridioides difficile, and respiratory syncytial virus (RSV). The Public Health Agency of Sweden presents the results of the voluntary laboratory reporting in reports during the winter season. For caliciviruses and RSV it also includes the results from other surveillance systems.
Laboratories also report denominator data for several analyses, including reports of the number of samples analysed for influenza, RSV, and calicivirus, as well as the number of patients tested for covid-19.
Sentinel surveillance means that only a selection of medical doctors or clinics report on the incidence of a disease or sample patients for surveillance purposes. Sentinel surveillance is used to sample patients with acute respiratory infection and influenza-like illness. Samples are analysed at the Public Health Agency of Sweden for influenza and SARS-CoV-2. Virological analyses of positive samples contribute to national and global surveillance. Through sentinel surveillance, the Public Health Agency of Sweden can monitor which influenza strains are circulating and whether vaccines and antivirals are effective, or whether resistance has developed.
The Public Health Agency of Sweden uses different types of syndromic surveillance to supplement traditional disease surveillance. Given the fact that the majority of people who become ill do not need to seek medical attention, it is hard to know how many people among the population have a certain illness. The traditional reporting systems only include those who seek medical attention. As a result, the number of reported cases is an underestimate of the proportion of the population that is actually affected. In order to respond to an epidemic in the best way possible, health services and society as a whole need to get rapid indications of the extent of transmission. This is done, for instance, by examining visitor search statistics from the regional medical advice website "1177.se".