Compilation of statistics for COVID-19 cases
Compilation of statistics for COVID-19 cases
THL's statistics on COVID-19 infections are based on data from the National Infectious Diseases Register. Previously, cases confirmed with a coronavirus test (PCR or antigen) were reported to the National Infectious Diseases Register by physicians as well as laboratories. As a result of a decree amendment, reports by physicians are no longer included starting 21st January 2022.
Decree on Communicable Diseases
What is a COVID-19 case?
Only cases confirmed with a laboratory coronavirus test (PCR or antigen) are recorded in the National Infectious Diseases Register. Not including reports by physicians does not reduce the number of confirmed cases because the National Infectious Diseases Register has combined the reports of each person made by laboratories and physicians.
How are cases recorded in the Infectious Diseases Register and why does the data sometimes change?
The register of infectious diseases automatically combines the laboratory and physician reports for the same person. As a result of this merging process, the daily numbers of cases may change.
New cases are recorded in the National Infectious Diseases Register according to the sampling date.
THL supplements the personal data for COVID-19 cases using the Population Information System. The system provides information about the patient's municipality of residence. This adjustment may change regional data if the background information of the persons, such as their place of residence – or place of care if place of residence is unknown – is verified and their cases are then recorded in a different area.
Which municipality or hospital district will a case be recorded in?
Each COVID-19 case is recorded for a specific municipality and hospital district in the following way:
- Primarily, the case is recorded for the person's home municipality or municipality of residence based on the information received from the Population Information System.
- If this information is not available, however, the case is recorded for the municipality of the person's place of treatment.
- If neither of the above is known, the case is recorded for the municipality of the laboratory where the specimen was taken.
- If the person is not registered in Finland, meaning that there is no information in the Population Information System about their municipality of residence, the COVID-19 case is recorded for the municipality where the place of treatment is located. If the place of treatment is not known, the case is recorded for the municipality of the reporting laboratory
Why are the daily numbers of new COVID-19 cases reported by THL different from the numbers reported by hospital districts?
New Covid-19 cases are reported in the National Infectious Diseases Register according to the date of sampling, which is used as the date of statistics.
Due to reporting delays, the date of statistics for a newly reported case in the National Infectious Diseases Register may be several days prior. Among other causes, these delays may relate to data transfer procedures.
In contrast, a hospital district may simply report the number of new positive results that have been diagnosed the same day.
Examples
Example 1: The daily numbers of cases differ in statistic by THL and the hospital district
If a sample has been taken from a person on 26 October and the test result is ready on 27 October, the hospital district may report the result immediately after obtaining it, on 27 October.
A new positive COVID-19 case is usually reported to the National Infectious Diseases Register with a one to three day delay. The data is recorded in the register according to the date of sampling, meaning 26 October in this case, even if the register receives the information on 28 October.
Example 2: The new case statistics have changed within a five day period
A person is from Kemi, which is located in the Western Ostrobothnia Hospital District. Their Covid-19 sample was taken in Rovaniemi, as they were being treated in the Lapland Central Hospital. Lapland Central Hospital is part of the Lapland Hospital District.
The municipality of the disease case recorded in the statistics is determined primarily on the basis of the municipality of residence obtained from the Population Information System, and only secondarily on the basis of the municipality of the place of treatment or the municipality where the testing laboratory is located. When the data was updated, the municipality for the case was changed from Rovaniemi to Kemi, according to the person’s municipality of residence. This also meant that the hospital district for the case changed from the Lapland Hospital District to the Western Ostrobothnia Hospital District.
Example 3: Moving to another region
In March, a COVID-19 patient was diagnosed while living in Vantaa, which is located in the Helsinki and Uusimaa Hospital District. The case was recorded in the Infectious Diseases Register for the Helsinki and Uusimaa Hospital District, even though the person later moves to Turku, which is located in the Southwest Finland Hospital District.
Example 4: Positive Covid-19 sample taken outside the municipality of residence
A person lives in Tampere, which is part of the Pirkanmaa Hospital District. They are spending the holidays in Espoo, and they go for a coronavirus test in the Helsinki and Uusimaa Hospital District. The test result is positive. Based on their municipality of residence, the case is recorded for Tampere and for the Pirkanmaa Hospital District.
