AGES radar for infectious diseases - 29.02.2024

The AGES Radar for Infectious Diseases is published monthly. The aim is to provide the interested public with a quick overview of current infectious diseases in Austria and the world. The diseases are briefly described, the current situation is described and, where appropriate and possible, the risk is assessed. Links lead to more detailed information. The "Topic of the month" takes a closer look at one aspect of infectious diseases.

Situation in Austria

Acute infectious respiratory diseases occur more frequently during the cold season, including COVID-19, influenza and RSV. These diseases are monitored via various systems, such as the Diagnostic Influenza Network Austria (DINÖ), the ILI (Influenza-like Illness) sentinel system and the Austrian RSV Network (ÖRSN). The situation in hospitals is recorded via the SARI (Severe Acute Respiratory Illness) dashboard.


Influenza is currently the predominant respiratory disease. COVID-19 cases in hospitals and SARS-CoV-2 signals in wastewater have fallen sharply after peaking in December and are currently at a low level. RSV appears to have peaked at the end of January.

The measures familiar from the pandemic can help to slow down the spread of all respiratory diseases: avoiding contact if you have symptoms, sneezing into the crook of your elbow, wearing suitable masks in appropriate environments and hand hygiene.

In wastewater monitoring, the SARS-CoV-2 virus concentration measured in December was higher than ever before. Since then, the concentrations have quickly decreased again and are now at a low level.

After peaking in December, the DINÖ is currently only recording isolated SARS-CoV-2-positive samples.

The number of COVID-19 patients in hospitals also peaked in mid-December. Since then, inpatient hospital admissions have decreased again: from 1,185 admissions to normal wards at the end of December to 132 in the second week of February. There has also been a sharp decline in intensive care units since the end of December, from 52 patients to 7 patients.

Austrian laboratories are sending SARS-CoV-2 samples to AGES for sequencing. The sequencing results are regularly published on the AGES website. The dominant variant since the end of last year is JN.1, daughter line of BA.2.86.

In Austria, free COVID-19 vaccination is available for everyone from the age of 6 months and is generally recommended for everyone from the age of 12. People over the age of 60 and those with an increased risk of a severe course of the disease are particularly recommended to keep their immunisation up to date. Further information on COVID-19 vaccination can be found in the current Vaccination Plan Austria 2023/2024 (Chapter E - COVID-19) dated 05/09/2023.

Coronavirus - AGES

In DINÖ, the number of influenza-positive samples is falling, after peaking at the beginning of February. Influenza subtype A(H1N1)pdm09 is currently predominant. Influenza B is increasing in the sentinel system samples, albeit at a low level.

The estimated number of influenza and influenza-like illnesses is shown on the AGES website. After an increase in mid-January, the numbers have fallen again in the last two weeks.

Hospital admissions have doubled since December. In calendar week (CW) 5, 595 people with influenza were admitted to a normal ward, compared to 284 influenza patients four weeks earlier. However, the peak appears to have been passed, with a decline again in the second week of February.

Details on the last influenza seasons can be found in the AGES Radar of 05.10.2023.

Vaccination effectiveness is high overall compared to other years, as current studies show, for example Eurosurveillance | Early influenza vaccine effectiveness estimates using routinely collected data, Alberta, Canada, 2023/24 season.

Influenza - AGES

Since the peak at the end of January, the number of RSV-positive samples has been decreasing. However, the positivity rate is still above 10% in calendar week 7. This indicates that the virus is still circulating strongly.

Hospital admissions to normal wards have increased in recent weeks: from 293 in the first week of the year to 417 in the first week of February. The majority of admitted patients are infants and young children aged 0 to 4 years.

The respiratory syncytial virus, RSV for short, triggers respiratory diseases. The RSV season in Austria usually begins in November and lasts until April. Infants, young children and people over the age of 60 have an increased risk of contracting RSV.

Since autumn 2023, two vaccines have been available in Austria to prevent RSV-triggered lower respiratory tract diseases in adults. Both vaccines are authorised from the age of 60 and are generally recommended as a single dose in accordance with current national recommendations. In addition, one of the two vaccines, Abrysvo, is authorised for pregnant women for the passive protection of newborns.

Further information on RSV vaccination can be found at Vaccination plan Austria 2023/2024 (


As of 27 February 2024, 167 confirmed cases have been reported in Austria for the current year, compared to 186 for the whole of 2023.

Who is infected?

This year, the confirmed cases are aged between 0 months and 62 years with a median age of 15 years. Most cases are in the age groups over 30 years and 10-14 years. The highest incidences are found in infants, in addition to the 10-14 age group. Of those infected this year, 97 are male and 70 female.

Most of the cases last year and this year were unvaccinated and could therefore have been easily avoided.

In general, all federal states except Carinthia are affected, with the highest number of cases so far this year in Tyrol, Lower Austria and Vienna.

In 2023, 49 (28.2%) of the 174 measles cases for which information was available were hospitalised, including one person in intensive care. In 2024, 33 (20.9%) of the 158 cases with relevant information have so far been registered as hospitalised, three of them in intensive care (as of 27 February 2024).

Epidemiological surveys and the determination of the genotype of the viruses can partly determine how the cases of the disease are related: Since the beginning of November, five different genotypes have been circulating in Austria, initially focussing on Vienna, but now also in all other federal states except Carinthia. Most cases can be attributed to various smaller and larger incidents, but there are also some cases that cannot yet be categorised in chains of infection.

Measles is a highly contagious viral disease. Infections are characterised by flu-like symptoms and a characteristic skin rash. In some cases, life-threatening complications such as inflammation of the lungs and brain can occur.

The best prevention against measles is vaccination. It is safe and provides a high degree of protection against infection, severe progression and passing on the virus. In Austria, a total of two vaccine doses are generally recommended from the age of 9 months (a joint vaccine with mumps and rubella). The vaccination is free of charge regardless of age and is available at all public vaccination centres. Missing vaccinations should be made up for at any age.

Effectiveness of the measles vaccination

According to the RKI, studies show that a single vaccination against measles protects 92% of those vaccinated against measles. It also protects against further spread among household contacts to the same extent. The effectiveness of the double vaccination against measles in Germany is 98% to 99%.

In order to protect infants who are still too young to be vaccinated, but who are at a higher risk of a severe course of measles infection, it is crucial that the entire neighbourhood is vaccinated. If older siblings have been vaccinated twice, it is extremely unlikely that they will bring the virus home with them, for example from school or kindergarten.

Further information on the measles-mumps-rubella vaccination can be found in the Austria 2023/2024 vaccination plan (

Measles - AGES

International outbreaks

Respiratory diseases continue to circulate at a high level in Europe and the USA . This is mainly due to influenza. RSV is decreasing overall in the EU. SARS-CoV-2 activity in the EU countries is low. In the USA, COVID-19 and RSV activity is also declining in many areas of the country.

In the last two weeks, the high influenza activity in the EU appears to be decreasing slightly.

COVID-19 admissions to hospital and intensive care units, as well as COVID-19 deaths in the EU, have been declining in all reporting countries since the end of December.

The currently reported figures do not accurately reflect the COVID-19 infection situation, as the number of tests and reports has decreased worldwide.

SARS-COV-2 variants

Currently, neither the WHO nor the ECDC classify any virus variant as a Variant of Concern (VOC), so no virus variant is classified as a variant of concern.

JN.1 is a sublineage of BA.2.86 and accounts for the majority of this variant, which is the most common lineage with a prevalence of 92%(ECDC, as at 26 February 2014). On 19 December, the WHO upgraded JN.1 itself to a VOI as it is spreading rapidly. So far, JN.1 is not considered more dangerous than other variants, which is why the WHO considers the risk it poses to be low.

The level of sequencing is low worldwide.

You can find more detailed information on the international variant situation at Coronavirus - AGES

A health emergency was declared in Rio de Janeiro and other cities and states in Brazil at the beginning of February. The reason for this is the very high number of dengue infections. By the end of February 2024, there were 991,017 dengue cases in Brazil, almost half as many as in the whole of 2023 (as at 26 February 2024). Deaths due to dengue in January 2024 were also many times higher than in the same period of the previous year. (As of 16/02/2024).

Dengue waves normally occur every four to five years in Brazil. The extremes in the current number of cases are explained by a combination of two factors: heavy rainfall due to the El Niño weather phenomenon and the heat favoured the proliferation of the yellow fever mosquito, Aedes aegypti, the vector of the dengue virus.

The majority of those infected do not develop the disease. Some infections lead to severe dengue fever, which manifests itself in fever, rash and head, muscle, limb, bone and joint pain. Around 2 to 4 per cent of infections lead to dengue haemorrhagic fever (DHF), which can result in organ failure.

The dengue virus (DENV) has four serotypes: DENV-1, DENV-2, DENV-3, DENV-4. Infection with one serotype confers long-term immunity to that one serotype, but not to the others. A second dengue virus infection with a different serotype increases the risk of severe disease. This is another reason why Brazil is currently experiencing such a devastating outbreak: all four serotypes are circulating, including those that have not been in circulation for 20 years.

Emergency centres have been set up in Brazil to test and, if necessary, treat the population. The carnival, which took place in Rio de Janeiro from 9 February to 17 February 2024, exacerbated the situation. City workers have the task of eliminating breeding grounds for mosquitoes in Rio by finding and emptying containers with standing water, including on rubbish dumps and roofs. An emergency campaign to immunise children in regions where the infection rate is highest has also been launched. This is being carried out with the Qdenga double vaccination.(New York Times, as of 16 February 2024)

Qdenga is approved in Austria, but is currently not generally recommended when travelling to endemic areas. The probability of a dengue infection during a tropical holiday is currently less than 0.2 percent. However, when travelling to risk areas, precautionary measures such as adequate protection against mosquito bites are recommended. The Federal Ministry for European and International Affairs calls on people travelling to Brazil to protect themselves from mosquito bites by using insect repellent, appropriate clothing and the like. (Status: 26/02/2024)

The Brazilian vector of dengue, the yellow fever mosquito Aedes aegypti, is not yet native to Europe. However, the Asian tiger mosquito, Aedes albopictus, which can also transmit the dengue virus, has been able to spread in large parts of Europe, especially in the south. In France, Italy and other European countries where populations of the Asian tiger mosquito are already established, there have already been local dengue cases (as of 26 February 2024). In Austria, the occurrence of the Asian tiger mosquito is monitored by AGES. Ovitrap monitoring - the monitoring of alien mosquito species - and the citizen science project "Mosquito Alert" have already detected Aedes albopictus in all Austrian federal states. Established populations of this species exist in parts of Vienna and Graz. To date, no cases of dengue infections acquired in Austria have been reported, although several cases imported from abroad are registered each year.

Italy has raised the dengue warning level at airports and harbours, partly due to the situation in Brazil.

Dengue - AGES

Topic of the month

The gardening season starts at the beginning of spring, and a very warm February has probably already inspired many people to start tidying up. Sheds, attics and gardens are cleaned for the first time. Wherever rodents are present and leave their droppings behind, there is a certain risk of hantaviruses being present in the air.

Hantaviruses are found all over the world and cause diseases of varying severity. They are transmitted from infected rodents to humans. The animals' urine, faeces or saliva contain the viruses. These droppings are stirred up during tidying and cleaning and the viruses are inhaled. Transmission can also occur via dirty hands or directly through a mouse bite. Human-to-human transmission is unlikely to occur. In Austria, transmission mainly occurs via the bank vole. In many cases, the infection is asymptomatic. In rare cases, the virus can cause haemorrhagic fever with kidney involvement or cardiopulmonary syndrome, in which the heart and lungs are affected.

Spring cleaning in areas where mice are found is the greatest risk of contracting hantaviruses in Austria. Other infection scenarios can include hiking or forestry work or working in an enclosed space where mice also live.

Avoid infection with hantaviruses

There is currently no authorised vaccination against hantaviruses. Therefore, the most important measure is prevention: Contact with rodents and their faeces should be avoided. In living or working areas, such as cellars, attics, sheds or similar, rodents should be controlled and hygiene should be prioritised.

Protective measures such as respiratory masks and gloves are important when tidying and cleaning in such an environment. Before a room is cleaned, it should be ventilated as well as possible: Open windows and doors for at least 30 minutes; to prevent infectious dust from being stirred up, dead mice, traps and droppings should be sprayed with disinfectant beforehand.

The following measures can help prevent rodents from getting out of hand in the home and garden:

  • Close rubbish bins
  • Always store food and animal feed in closed containers
  • Do not put leftover food in the compost
  • Seal off loopholes and possible access points to living areas
  • Set up snap traps: good baits are peanut butter, cheese or nougat cream

Seasonal clusters

Most infections occur in spring. However, not every year is the same; the number of infections depends heavily on the number of rodents. The numerous cases in Styria in 2021 (183 reported cases) are probably due to a strong growth in the red-backed vole population. The annual fluctuations in population density are related to the food supply for the mice: Every two to three years there are particularly large numbers of beechnuts in the forests (beech mast years) and therefore also particularly large numbers of bank voles.

In Austria, 97 cases of hantavirus disease were reported in 2023, 87 of them in Styria. However, hantavirus is under particular scrutiny there and suspected cases are more likely to be tested for hanta than in the other federal states. As most infections are harmless, it is mainly those that require hospital treatment that are registered. The last years with a particularly high incidence were 2019 and 2021. 2024 is not expected to be a particularly strong red-backed vole year by the experts at the Institute of Forest Ecology at the University of Natural Resources and Applied Life Sciences, as seed production in the forest was below average last autumn.

Hantavirus - AGES

List of Austrian reference centres


Dirk Werber has headed the Institute of Infection Epidemiology at AGES since February 2024. Werber moved to AGES from the Berlin State Office for Health and Social Affairs, which he had headed since 2015. The trained veterinarian and habilitated epidemiologist previously worked at the RKI for 15 years.

The core topics of his work are the surveillance of infectious diseases and the investigation of disease outbreaks. Werber completed his training as an epidemiologist in Canada and took part in a two-year European training programme (EPIET) in Wales. He has worked as a consultant for the WHO on international assignments.

AGES is delighted to welcome Dirk Werber to its team!

The Yersinia annual report for 2023 was published on 29 February 2024.

Yersiniosis is a food-borne infectious disease caused primarily by bacteria of the species Yersinia(Y.) enterocolitica and, more rarely, Y. pseudotuberculosis. The main reservoir for Y. pseudotuberculosis is various mammals, in the case of Y . enterocolitica the pig, whose tonsils are often colonised. Transmission usually occurs via contaminated food (meat, dairy products, water). As the bacteria can also multiply at 4 °C (e.g. in the refrigerator), heating meat dishes through is an important preventative measure. Direct transmission from infectious animals to humans or from person to person is rare. Repeated transmissions through contaminated blood products have been documented.

The diseases caused show a broad spectrum. The majority of yersinioses are caused by enteropathogenic Y. enterocolitica (>90 %), less frequently by Y. pseudotuberculosis. Infants and young children usually develop acute gastroenteritis with vomiting, watery to bloody diarrhoea and fever, which heals on its own after one to two weeks. Acute mesenteric lymphadenitis accompanied by abdominal pain is typical of yersiniosis in schoolchildren and adolescents. The clinical picture can resemble an inflammation of the image bowel ("pseudoappendicitis"). Different clinical forms occur in adults, such as flu-like infections with pharyngitis and fever.

Y. enterocolitica tends to lead to a gastroenteritic clinical picture (gastrointestinal complaints), Y. pseudotuberculosis more frequently to pseudoappendicitis.

The National Reference Centre for Yersinia has been located at the AGES Institute of Medical Microbiology and Hygiene in Graz since 2011. In 2023, as of 30 January 2024, a total of 100 cases of yersiniosis were reported to the Federal Ministry of Social Affairs, Health, Care and Consumer Protection and a total of 192 initial human isolates were sent to the National Reference Centre for Yersinia.

The clinical course of 31 of the reported cases was reported:

  • twenty-one cases with diarrhoea (67.7 %)
  • five cases with abdominal pain (16.1 %)
  • two cases with vomiting (6.4 %)
  • eight cases with fever (25.8%)

A 9-year-old patient with symptoms of abdominal pain and fever underwent an appendectomy.

Yersiniosis is a rare disease in Austria compared to other diarrhoeal diseases such as campylobacteriosis and salmonellosis.

In 2023, there were no indications of disease clusters.

Yersinia - AGES

In Austria, most HIV-infected people are recorded and treated in the HIV cohort (AHIVCOS). An association of now nine clinics looks after patients according to a standardised system and enables comparative research.

The development of HIV in Austria is presented annually in a comprehensive cohort report. A summary of the 2023 report can be found here.

Technical term epidemiology

Every month we present a technical term from the field of infectious disease epidemiology, starting with the basics:


The word epidemiology is derived from the ancient Greek words epi, meaning "on or about"; demos, meaning "the people or people"; and logie, meaning "study or teaching". Epidemiology is an interdisciplinary science that deals with the frequency and distribution of diseases in the population, analyses their possible causes and carries out risk assessments.

The RKI specialist dictionary refers to a WHO definition, according to which epidemiology is the "study of the distribution of diseases, physiological variables and social consequences of disease in human populations and the factors that influence this distribution."

Epidemiology analyses various questions:

  • What health conditions occur in a given population?
  • What factors contribute to the spread of these conditions?
  • What consequences do they have?

Health conditions can include, for example, diseases or risks, but also factors that have a positive effect on health.

In contrast to clinical medicine, epidemiology does not focus on individual sick people, but looks at all factors and interactions within a population that influence health and disease. According to the RKI, the subject of epidemiology is cases of illness, disability or death in a population as well as all factors that threaten or influence the health of a particular population, be they physical, chemical, biological, social, cultural or behavioural factors.

As a scientific discipline, epidemiology offers a collection of methods for recognising and combating threats to life or health. With the aim of epidemiology to record the health status of populations and derive possibilities for targeted improvement, epidemiology is also an important sub-discipline of the health sciences and an essential pillar of public health.


The next AGES-Radar will be published on 28 March 2024.

Last updated: 29.02.2024

automatically translated