Contact tracing was used at the beginning of the outbreak. Until March 12th 2020 all suspected cases among people travelling from affected areas to Sweden were followed up with sampling and contact tracing. On March 12th, the efforts entered a new phase focusing on delaying the spread of infection in the population, and at the same time protecting the oldest and most fragile against the disease. Since the summer some counties have started with contact tracing again, some taking a special focus on long term care facilities.
The Public Health Agency published a new guidance on contact tracing for COVID-19, valid from 23 July 2020. Every person with confirmed Covid-19 has a responsibility to protect others from becoming infected, and has a mandatory obligation to inform close contacts that he or she has tested positive. Instructions on what information is to be given to the contacts is provided when the positive diagnosis is obtained. In addition, some regions have employed dedicated personnel that will help with contact tracing.
The Public Health Agency uses several different surveillance systems to monitor the spread of COVID-19 in Sweden. Systems used for surveillance of COVID-19 include:
• Number of deaths: The number death with laboratory confirmed COVID-19, regardless of the cause of death. In addition, all-cause mortality compared to expected death is analysed every week.
• Number of patients in intensive care: Data on the number of patients in intensive care are collected from the Swedish Intensive Care Registry (SIR) every day.
• Number of hospitalised patients: COVID-19 is subject to mandatory reporting under the Communicable Diseases Act, physicians and laboratories continuously supply data that are analysed by the Public Health Agency every day.
• Number of patients seeking care: In addition to the mandatory reporting under the Communicable Diseases Act, a selection of primary care providers work with sentinel surveillance, reports the incidence of infection, and sends samples to labs. Statistics from the medical advice service 1177 (web searches and telephone calls) are also used to monitor the situation.
• Proportion of the population infected: The Public Health Authority is conducting samples to measure the prevalence of COVID-19 in the population. Randomly selected persons are asked to participate in the sampling.
• March 13th. Hospitalised patients and people working in health care or care for older people, with suspected COVID-19 are prioritized for sampling. Until March 12th 2020 all suspected cases among people travelling from affected areas to Sweden were followed up with sampling and contact tracing.
• March 20th. The regional administrative boards (Länsstyrelserna) have been tasked with presenting a status report on the spread in the different regions, including long-term care facilities and/or home care. The Health and Social Care Inspectorate (IVO) shall retain a supervisory role.
• March 27th. The Public Health Agency are undertaking testing in Stockholm to assess the level of COVID-19 in the community. A randomly selected group of 650 people that are part of the Agency’s regular survey panel are asked to participate by providing samples from their nose, pharynx and saliva. Results of the testing showed that 2.5% of participants tested positive for the SARS-CoV-2 virus.
• April 7th. The Public Health Agency are undertaking testing nationwide to assess the level of COVID-19 in the community. A randomly selected group of 4,000 people that are part of the Agency’s regular survey panel are asked to participate by providing samples from their nose, pharynx and saliva.
• April 8th. The Public Health Agency is using aggregated data from Telia (the partly state-owned telecoms company) to trace patterns of movement among Swedes connected to the spread of COVID-19.
• April 17th. A new strategy for sampling is presented. Testing will primarily be for patients and people in the health care and social care systems. Secondly, for health care and social care personnel and thirdly, for people in other essential sectors.
• April 23rd. The Public Health Agency presents results from modelling of the spread of COVID-19 in the county of Stockholm. According to the results, around 25% of the population in the county of Stockholm will have had COVID-19 on May 1st.
• April 27th. The National Board of Health and Welfare publishes statistics of death caused by COVID-19 based on the national register of cause of death. The statistics include all cases where the underlying cause of death was COVID-19, regardless of whether the diagnosis was laboratory confirmed or not (while The Public Health Agency include number of deaths with laboratory confirmed COVID-19). The new statistics, which have a delay of 3-4 weeks, show about 10% more deaths caused by COVID-19 compared to The Public Health Agency’s statistics.
• April 29th. The Public Health Agency announced new nationwide testing to assess the level of COVID-19 in the community. The setup will be the same as the random sampling which were started April 7th.
• May 12th. At the end of April, about 1 percent of the population in Sweden had an active covid-19 infection. In Stockholm 2.3 percent had an active infection.
• May 20th. The Public Health Agency announced results from an ongoing study of antibodies against SARS-CoV-2. The results reflect the situation in April. The largest proportion of positive antibody tests were in the county of Stockholm, where 7.3% had antibodies against SARS-CoV-2. In the county of Västra Götaland, the county with the second largest population, 3.7% of the population had antibodies and in the county with the third largest population, Skåne, showed that 4.2% percent had antibodies.
• June 18th. The Public Health Agency announced results showing that at the end of May, about 0.3 percent of the population in Sweden had an active covid-19 infection. In Stockholm 0.7 percent had an active infection.
• June 18th. The Public Health Agency published results from antibody tests from blood donors. The results show that the proportion of blood donors with antibodies to covid-19 was 1.6 percent at week 17 and had changed to 5.0 percent at week 22.
• June 18th. The Health Agency published results from antibody test collected from blood samples taken in outpatient care on other medical indication than Covid-19. At the end of May, 6.3 percent of the studied population had Covid-19 antibodies.