Explanation of concepts

All statistics are continuously updated. Consequently early statistics may be changed with time.

• Clinical notification
• Country of infection
• County
• Data sets
• Diseases
• Graph
• Incidence
• Interactive map
• Laboratory notification
• Moving average
• Total number of cases

Diseases

The surveillance of communicable diseases is regulated by the Communicable Disease Act (CDA). The CDA is due for review but at present there are 54 diseases requiring statutory notification. The Swedish Institute for Communicable Disease Control monitors these 54, notifiable, infectious diseases.

A double reporting system is used for each case of an infectious disease. The two reports emanate from the doctor treating the patient (see "Clinical notification") and from the laboratory where the causative agent is identified (see "Laboratory notification""). This double reporting system considerably increases the sensitivity of the surveillance.

Interactive map

Interactive map over Sweden with the possibility to get statistics on county level. There are two types: Incidence map and Total map, which both illustrate the tabled information.

The maps may be used to compare disease levels in a specific area with the previous "normal" levels or to compare levels of disease between counties. Differences between counties may be due to an outbreak, but are more often due to other causes, e.g. differences in laboratory culturing protoclols or differences of chance.

The maps require Internet Explorer or Netscape with version 4 or later.

Graph

There are two types of graph: a graph showing the number of cases per week and a trend graph (see "Moving average"). Both show the number of number of cases per week in Sweden over the previous four years.

Country of infection

In the clinical notification (see "Clinical notification"") the patient is asked to name the country that is most likely to be the source of the infection. Occasionally this information is missing. Most commonly, the explanation for this is the presence of a laboratory notification and the absence of clinical notification (see "Laboratory notification").

Clinical notification

The clinical notification includes information of epidemiological relevance, e.g. clinical diagnosis, suspected source, route of infection, risk group, etc. The notification must be done within 24 hours of the diagnosis. For some diseases this period can be one week.

Laboratory notification

The laboratory notification must be done within 24 hours from the identification of the causative agent. For some diseases, like Penicillin-resistant pneumococci infection (PRP) bofore year 2000, this notification is done on a voluntary basis.

County

There are 21 counties in Sweden. The notification system is based on reporting in each county. The county names are abbreviated as follows:

Blek Blekinge
Dlrn Dalarna
Gotl Gotland
Gävl Gävleborg
Hall Halland
Jmtl Jämtland
Jkpg Jönköping
Kalm Kalmar
Kron Kronoberg
Nbtn Norrbotten
Skån Skåne
Sthm Stockholm
Södm Södermanland
Upps Uppsala
Vrml Värmland
Vbtn Västerbotten
Vnrl Västernorrland
Vstm Västmanland
Vgöt Västra Götaland
Öreb Örebro
Östg Östergötland

Total number of cases

The total number of reported cases includes those with a single notification from either a clinical (see "Clinical notification") or a laboratory source (see "Laboratory notification").

Incidence

The incidence is the number of cases per 100 000 population within a certain period of time. The population per county for the current year is not yet known. The incidence for the current year is therefore calculated on the previous year’s population.

Note that the time interval is not important. An incidence is calculated by taking the number of cases (in the specified period) multiplied by 100.000 and dividing it by the total population:

100.000*[Total number of cases]/[population]

Data sets

The Clinical notification (see "Clinical notification") indicates the probable country of infection (see "Country of infection"). This web service provides three different sets for the statistics:

• Domestic cases - all cases infected in Sweden.
• Cases infected abroad - all cases infected in any country other than Sweden.
• All registered cases.

The sum of the domestic cases and the cases infected abroad, does not always equal total of all registered cases. This is because the information, on the clinical notification, regarding the country of infection is missing. This may be explained by an error or absence of the clinical notification and the presence of a solitary laboratory notification (see "Laboratory notification").

Moving average

The moving average is an attempt to filter small fluctuations in the data and focus on the trends.

A moving average shows the average number of cases per week for the last n weeks. When the number of cases per week increase or decrease, the moving average will increase or decrease as well. The moving average graph contains two moving averages, one short (six weeks) and one long (52 weeks) (see "Example of Analysis" for more information).