A review of respiratory viruses

The influenza and RSV season is over. Respiratory viruses are showing low levels of activity across all surveillance systems. In the other Member States of the European Union and the European Economic Area (EU and EEA), the number of people reporting symptoms of a viral respiratory infection also remains low.

Following the end of the flu season in Austria, only isolated cases of influenza were detected. The flu season lasted a total of 12 weeks: from early December 2025 to mid-February 2026. It began four weeks earlier than in the previous season and lasted three weeks less. Two peaks were observed: in the first week of January with a positivity rate of 47% and at the end of January with a positivity rate of 34%.

In contrast to previous seasons, the influenza cases detected were almost exclusively due to influenza A, with the A(H3N2) subtype dominating. Influenza B was detected in only 1% of all samples.

Hospital admissions due to influenza infection showed a higher peak than in the previous season. At the peak in 2025/2026, 894 admissions per week were recorded, compared with the peak of the 2024/2025 season, when 703 admissions per week were reported.

Influenza virus activity has declined to inter-seasonal levels in almost all EU and EEA countries. Only a few cases and hospital admissions are now being reported across all age groups.

The best preventive measure against severe disease progression and potential complications of influenza is the annual influenza vaccination. The influenza vaccination is available free of charge for all age groups under the public vaccination programme. In Austria, vaccination against influenza (true flu) is recommended from the age of 6 months, particularly for people at risk of severe illness and their social contacts, as well as those with an increased risk of infection due to their living circumstances or occupation. Ideally, the influenza vaccination should be administered in mid-October or November, before the flu season begins. Further details can be found at www.impfen.gv.at/influenza and in the current Austrian Vaccination Schedule 2025/2026.

The results of a study published in April 2026 suggest that the influenza vaccination can reduce the risk of short-term cardiovascular events, such as heart attacks, even in the event of breakthrough infections.

At the end of February, the WHO published its recommendation for the influenza vaccine composition for the 2026/2027 flu season in the northern hemisphere. As influenza viruses are constantly changing, the vaccines must also be regularly adapted. During this year’s consultation, particular attention was paid to ‘subclade K’, a markedly different variant of the A(H3N2) virus that emerged in August 2025 and spread rapidly worldwide. 

In episode 003 – Influenza & Co: How do I navigate the flu wave safely? of the AGES podcast “Mut zum Risiko”, infectious disease epidemiologist Fiona Költringer explains what the flu is all about and how best to protect oneself against it. 

Flu - AGES

The respiratory syncytial virus (RSV) outbreak lasted a total of nine weeks, from February to April. The peak was reached at the end of February, with a maximum positivity rate of 22%. This maximum positivity rate was significantly higher than in the previous year. A higher peak in hospital admissions due to RSV infection was also recorded compared with the previous season: at the peak, there were 341 admissions per week, twice as many as at the peak of the 2024/2025 season.

In the EU and the EEA, RSV remains the main cause of current respiratory virus activity, particularly in cases of severe illness. Current circulation is low and declining. The rate of decline has slowed compared with recent weeks, suggesting that the RSV season is coming to an end.

Children under five and people over 65 are at particularly high risk of developing severe RSV infection. Passive immunisation using monoclonal antibodies is therefore recommended for infants, and the RSV vaccine is recommended for adults aged 60 and over. Further information on this is available at impfen.gv.at/impfungen/rsv and in the current 2025/2026 vaccination schedule. 

RSV - AGES

Fluctuating activity at a low level has been observed for SARS-CoV-2 throughout the autumn and winter months. There is still no sign of seasonal circulation coinciding with the flu season. A decline in hospital admissions for COVID-19 has been observed over recent years. 

Whilst the overall burden remains very low at European level, the first signs of ongoing SARS-CoV-2 transmission are emerging in doctors’ surgeries. 

Information on COVID-19 vaccination can be found at impfen.gv.at/covid-19 and in the Austrian Vaccination Schedule 2025/2026.

Coronavirus - AGES

The annual report on tick monitoring for 2025 was published on 4 May. In total, AGES received 8,298 ticks last year from almost all of Austria’s federal states. Tick activity began as early as February, with most ticks being sent in during April. Of 3,838 hard ticks of the genera Ixodes, Dermacentor and Haemaphysalis, 24% tested positive for Lyme borrelia. The most common species of borrelia was Borrelia afzelii.

In 2026, AGES had already received 1,720 ticks from Austria (as of 06/05/2026). The first ticks were reported this year at the beginning of February. AGES received the most ticks from Upper Austria (739; 43.0%), followed by 423 ticks from Lower Austria. At the end of April, the first confirmed Hyalomma tick of the year was identified in Styria. As was the case last year, the genus Ixodes has dominated so far, with Dermacentor accounting for only 2.9%. 

Ixodes is considered the most common carrier of Lyme disease in Austria. Alongside Lyme disease, early summer meningoencephalitis (ESME) is one of the most common tick-borne diseases. In 2026, the ESME vaccination programme in Austria will celebrate its 50th anniversary. A study published in October 2025 calculated that the TBE vaccine prevented more than 10,000 hospitalisations, 4,000 severe cases of TBE and 80 deaths between 2000 and 2024. A total of 146 TBE cases were reported in Austria in 2025, and four since the start of 2026 (as of 20 May 2026).

Austria is considered a high-risk area for tick-borne diseases; therefore, it is advisable to follow the key recommendations: consistent protection against ticks when outdoors, prompt removal of ticks from the skin, and the TBE vaccination. As the start of the season for TBE cases has shifted earlier to March/April in recent years, both the primary vaccination and booster jabs should be administered before the start of the tick season in January/February. More information can be found in the Austrian Vaccination Schedule 2025/2026.

Whilst there is a recommended and effective vaccine against the TBE virus, there is no approved vaccine against the Borrelia bacteria. According to a press release from the manufacturer, a first vaccine candidate demonstrated 70% efficacy against Lyme disease in a Phase 3 trial. The vaccine targets several variants of the Lyme bacteria found in Europe, which are also present in Austria.

TBE - AGES

Tick information – AGES

On 2 May, the World Health Organisation (WHO) reported the first outbreak of hantavirus on a cruise ship. As of 20 May 2026, the ECDC has reported a total of eleven cases, including nine laboratory-confirmed and two probable cases, three of which were fatal. All known cases of hantavirus to date have been passengers or crew members of the cruise ship. Due to the potentially long incubation period of six weeks, further cases could still emerge internationally.

There are several virus species within the genus Orthohantavirus (commonly known as hantaviruses) that differ from one another. Transmission usually occurs via rodents through inhalation of infectious excretions. In Austria, for example, bank voles are the main carriers. Human-to-human transmission has only been documented for one virus type, the Andes virus, although transmission here too occurs mainly via rodents. The Andes virus was detected in the cases linked to the cruise ship. This virus type is found primarily in Chile, Argentina and other South American countries; it has never been detected in Austria to date. 

The cruise ship docked in Tenerife (Canary Islands, Spain) on 10 May; the evacuation of passengers and parts of the crew was completed on 11 May. This involved 149 people from 23 countries. They are currently undergoing country-specific quarantine in various countries. All persons on board are considered high-risk contacts. The ship has since returned to the Netherlands. 

There were no Austrian citizens on board the affected ship, nor are there any known high-risk contacts with links to Austria. Two people who were briefly in the vicinity of a confirmed case on an aircraft were classified as low-risk contacts in Austria and informed by the health authorities of the relevant Austrian recommendations. Actual infection is considered unlikely.

One hypothesis regarding the origin of the outbreak is that the first case became infected in Argentina before boarding the cruise ship, where the virus occurs repeatedly in animals. During the voyage, the virus was transmitted to other people on board. The ECDC assesses the risk of the general population in the EU or the EEA becoming infected with the virus as very low. The WHO, the ECDC, the European Commission and the EU/EEA Member States, as well as other affected countries, are working closely together and monitoring the situation. 

Up-to-date information on the situation can be found at:

ECDC: Andes hantavirus outbreak on cruise ship 

WHO Disease Outbreak News Updates

On 5 May 2026, the WHO was informed of an outbreak with a high mortality rate in the Democratic Republic of the Congo (DRC). Subsequently, on 16 May 2026, the WHO declared a Public Health Emergency of International Concern (PHEIC) due to an Ebola outbreak in the DRC and Uganda. As of 19 May, over 500 suspected cases and 130 deaths had been reported in north-eastern regions of the DRC, with 30 cases confirmed by laboratory testing. Uganda has so far identified two cases, both involving individuals who had entered the country independently from the DRC. (ECDC, as at 19 May 2026) Among the confirmed cases in the DRC is a US doctor. He and his close contacts were transferred to Germany for treatment (CDC, as at 18 May 2026).

The outbreak is caused by the Bundibugyo virus (BDBV), which triggers a severe and often fatal form of Ebola disease. There is currently neither an approved vaccine nor specific treatments for the Bundibugyo virus or Bundibugyo virus disease; early supportive symptomatic treatment is essential. The case fatality rate for this Ebola variant in past outbreaks has ranged between 30 and 50%. Fruit bats are suspected to be the natural reservoir. Transmission occurs through contact with infected wild animals or through direct contact with the bodily fluids of infected humans. 

Containing the current outbreak is complicated by several factors: the outbreak was detected late; there was a four-week gap between the onset of symptoms in the suspected index case and laboratory confirmation of the outbreak, which facilitated the spread of the virus. The simultaneous circulation of arboviruses and influenza viruses, which can only be distinguished from the Ebola virus by laboratory testing, makes it difficult to detect Ebola. The region is characterised by conflict, which limits the possibilities for surveillance and contact tracing. Furthermore, the high mobility of the population in the border region increases the risk of further spread. Uganda has postponed the ‘Martyrs’ Day’ celebrations, which were due to take place on 3 June, due to the high risk of infection. Up to two million people attend this annual religious and national event, including thousands of pilgrims from the east of the DRC. 

Although information remains limited, the ECDC assesses the likelihood of infection for people living in the EU/EEA as very low. The rapidly changing situation is being monitored very closely.
 

Bangladesh is currently experiencing its worst measles outbreak in decades. Having recorded just 125 cases of measles last year, a sharp nationwide rise in case numbers has been observed since January 2026. In the period from 15 March to 14 April 2026 alone, 19,161 suspected cases and 2,973 laboratory-confirmed measles cases were reported, of which 166 and 30 patients respectively subsequently died, and 12,318 hospital admissions were recorded (WHO, as of 23 April 2026). In almost 80% of cases, the patients were children under the age of five. Deaths were also observed mainly among unvaccinated children under the age of two. 

Prior to this outbreak, Bangladesh was on the path to measles elimination. Thanks to high vaccination coverage rates in the routine immunisation programme – two doses of the measles-rubella vaccine at 9 months and between 15 and 18 months – and the successful implementation of nationwide vaccination campaigns every four years in close collaboration with the United Nations Children’s Fund (UNICEF), case numbers had fallen rapidly. In addition, vitamin A campaigns were carried out twice a year to reduce the risk of severe disease and deaths.

As a result of political upheaval following the 2024 revolution, combined with the discontinuation of cooperation with international partners, the high quality of the routine immunisation programme could not be maintained. Nationwide vaccination and vitamin A campaigns originally planned were, in some cases, suspended entirely. The resulting immunity gaps in a population with widespread undernutrition and malnutrition contributed to the emergence of this outbreak, which has seen a high proportion of severe cases and deaths. 

The new government, which has been in office since February 2026, has already taken steps to counter the outbreak. The agreement with UNICEF has been resumed and a nationwide emergency vaccination campaign launched in April.

The WHO assesses the risk for the WHO South-East Asia Region as high, particularly the risk of cross-border spread to the neighbouring countries of Myanmar and India. 

Globally, the risk is assessed as moderate due to high population mobility combined with ongoing, widespread measles transmission and existing immunity gaps. 

In Europe and Austria, measles case numbers have fallen significantly again compared to 2024 and 2025. In Austria, four cases have been reported so far this year. 

In the AGES Radar edition of 12 February 2026, we reported in detail on the WHO’s decision regarding the measles elimination status in Austria.

You can find the latest information on the measles situation in Austria on the AGES website: Measles – AGES

Alcohols (e.g. ethanol or propanol) are the classic group of active ingredients used in hand sanitiser. They act rapidly against vegetative bacteria, mycobacteria, fungi and many viruses, but are not sporicidal. Their rapid evaporation is practical, but can limit the required contact time when used on surfaces.

Oxygen-releasing agents (e.g. hydrogen peroxide or peracetic acid) act through oxidation and, depending on the formulation and concentration, have a very broad spectrum of activity, including sporicidal effects. They are used, amongst other things, for surfaces, medical devices and special decontamination procedures. 

Aldehydes (e.g. glutaraldehyde) also have a very broad spectrum of activity and can act as sporicides under suitable conditions. Due to their irritant effect, odour and occupational health considerations, they play a lesser role in routine surface disinfection today than in the past, but remain relevant for certain specialised applications. 

Halogens, particularly chlorine compounds, act rapidly and have a broad spectrum of activity. They are cost-effective and particularly useful for contaminated surfaces, but their efficacy can be reduced by organic material (e.g. blood). Thorough pre-cleaning is therefore essential. Depending on the concentration, they may also have a corrosive effect. Iodine compounds are primarily used for wound disinfection. 

Quaternary ammonium compounds are widely used surface disinfectants and, in addition to their disinfecting effect, also exhibit certain cleaning properties (e.g. grease removal). They are generally effective against vegetative bacteria and enveloped viruses, but not against spores and usually not sufficiently effective against mycobacteria or non-enveloped viruses. 

What does this mean in everyday life?

The use of disinfectants should always be tailored to the environment and the potential risk: 

In hospitals and other healthcare settings, disinfection is a targeted and integral part of infection prevention and the protection of patients and staff. Here, it is carried out in accordance with prescribed hygiene protocols and the expected range of pathogens. 

In the workplace, however, the need depends primarily on the task at hand and the individual risk (contact with biological material, food handling, frequent customer contact). There are strict regulations in this regard, particularly in the catering industry.

In the home, however, cleaning is usually more important than disinfection: washing hands, regularly cleaning kitchen, bathroom and high-touch surfaces, and washing textiles correctly are generally sufficient for everyday life. Disinfectants should primarily be used at home when specific circumstances require it, e.g. suspected infectious diarrhoeal diseases, flu season, or living with particularly vulnerable people in the same household.

Disinfection is considered ‘too frequent’ when it routinely and indiscriminately replaces normal cleaning, e.g. as daily surface disinfection throughout the home. This not only increases costs and the burden on the environment and individuals (e.g. skin irritation), but can also create a false sense of security. Furthermore, there is ongoing scientific debate as to whether excessive use of disinfectants may also lead to the selection of microorganisms with reduced sensitivity.

Conclusion

The choice of a disinfectant should therefore be based not on the broadest possible spectrum of activity, but on the specific spectrum required: as broad as necessary, as targeted as possible. Only when the spectrum of activity, method of application, concentration and contact time are all correctly matched can disinfection be reliably effective and sustainable. 

The 2025 annual report on botulism was published on 19 May 2026. 

Botulism (‘sausage poisoning’) is a form of poisoning caused by the bacterium Clostridium botulinum. The neurotoxins produced by this bacterium are among the most toxic of all naturally occurring substances. Botulism occurs in humans in three forms: foodborne botulism, infant botulism and wound botulism. The differences lie primarily in the route of entry for the neurotoxin produced by Clostridium botulinum.

In 2025, no cases of human botulism were documented by the National Reference Centre for Botulism in Austria. A total of 40 cases of the disease have been reported in Austria since 2000. The last case of botulism was identified by the National Reference Centre for Botulism in November 2024 in an 8-month-old male infant with botulinum neurotoxin gene B. In 2023, the National Reference Centre for Botulism in Austria documented two cases of human botulism: in a 41-year-old man with botulinum neurotoxin gene B and in a 34-year-old woman with iatrogenic botulism.

In human samples and food samples, toxin detection is carried out using a mouse bioassay and – where indicated – testing for Clostridium botulinum is performed using culture or molecular biological methods.

The 2025 annual report of the National Reference Centre for Diphtheria – Laboratory was published at the end of April.

In 2025, 209 samples were examined at the National Reference Centre. Following very high figures in 2022, the number of toxin-producing Corynebacteria detected remained at a low level, as had been the case in previous years. 

In 2025, potentially toxin-producing Corynebacteria were detected in 32 samples: 

• in 28 samples, these were Corynebacterium (C.) diphtheriae
• in four samples, Corynebacterium (C.) ulcerans 

In four of these isolates, the toxin gene was detected by PCR; three of these (two C. ulcerans, one C. diphtheriae) tested positive for toxin production using ELEK tests. No ELEK test was performed on one isolate as it was a multiple submission. The three samples in which toxin-producing Corynebacteria were detected originated from three patients. Of the three cases, two presented with cutaneous diphtheria (one caused by C. ulcerans, one by C. diphtheriae biovar mitis) and one with classic respiratory diphtheria (caused by C. ulcerans).

Resistance to the antibiotic erythromycin was detected in four C. diphtheriae isolates. One was a toxigenic strain, and three were non-toxigenic strains. No resistance to penicillins was detected. 

The clinical presentation of diphtheria is primarily caused by the action of the diphtheria toxin. Depending on the site of infection, diphtheria is classified into different forms: cutaneous diphtheria (skin lesion), respiratory diphtheria (mild respiratory diphtheria affecting the upper respiratory tract without the presence of an adherent membrane/pseudomembrane; classical respiratory diphtheria involving the upper respiratory tract with the presence of an adherent membrane/pseudomembrane). Classical diphtheria is a serious infectious disease that can be fatal without adequate treatment. 

A vaccine is available for prevention. Primary immunisation should begin in childhood, and regular booster doses are necessary to maintain protection. Details in the Austrian Immunisation Schedule 2025/2026.

Diphtheria - AGES

The ‘Long Night of Research’ took place in Illmitz at the end of April, attracting 450 visitors. 

AGES, in collaboration with the University of Veterinary Medicine, Vienna, was represented with a stand on the topic “What makes mosquito hunting so exciting for researchers?”.  

The session explained why mosquito monitoring programmes are necessary, which ones currently exist in Austria (pathogen monitoring in adults, tiger mosquito monitoring using ovitraps and Mosquito Alert), and various types of traps were presented. In addition to the adult traps and ovitraps currently used in monitoring programmes, other traps such as gravid traps and an emergence trap were also presented and explained. An adult trap was set up on site and emptied regularly – this allowed visitors not only to see the trap in action in the field but also to examine the catch under a microscope and, among other things, learn how to identify a tiger mosquito.

You can find more on this topic at: 

Information on mosquitoes & diseases – AGES

Austria-wide monitoring to record non-native mosquito species – AGES

Mosquito Alert app – AGES
 

In April and May 2026, the WHO confirmed that trachoma had been eliminated as a public health problem in Algeria, Australia and Tunisia. This brings the total number of countries worldwide to have achieved this status to 31. All three countries were able to combat the disease through long-term measures, with the implementation of the WHO’s ‘SAFE’ strategy (Surgery, Antibiotics, Facial cleanliness, Environmental improvement) playing a particularly important role 

In Australia, the focus was on remote Indigenous communities. In close collaboration with local communities and health services, regular screenings and targeted treatment took place in high-risk areas. Algeria also implemented targeted measures in particularly affected regions in the south, including mass treatment with antibiotics. Awareness campaigns were carried out, and water and sanitation services were expanded. Tunisia integrated eye treatment into primary healthcare and school health programmes and worked with communities to promote good hygiene.

Trachoma is a bacterial eye infection and the world’s leading infectious cause of blindness. It is caused by certain serotypes of the bacterium Chlamydia trachomatis (other serotypes are responsible for infections of the urogenital tract) and spreads through close physical contact, via flies and contaminated surfaces. Repeated infections can lead to scarring, entropion (inward turning of the eyelids) and irreversible blindness.

Trachoma primarily affects regions with poor hygiene conditions and a lack of access to clean water. A disease is considered ‘eliminated as a public health problem’ when a country achieves certain targets set by the WHO. Even after the disease has been officially eliminated as a public health problem, certain measures remain in place to ensure these targets continue to be met.

An observational study published in *The Lancet* in May 2026 examined the roll-out of the RTS,S/AS01_E malaria vaccine in Ghana, Kenya and Malawi since 2019 and summarises the key findings of this large-scale implementation programme. 

The vaccine led to a reduction in overall mortality among young children: according to estimates, it prevented one in eight deaths among children eligible for vaccination. Furthermore, fewer hospital admissions due to severe malaria were recorded in the regions where a vaccination programme was introduced. 

The results confirm that the vaccine is effective and safe. The vaccine offers additional protection against malaria alongside existing measures such as mosquito nets. Since 2024, the vaccine has been introduced in 25 further African countries, with plans underway in others.
 

Number of cases of notifiable diseases under the Epidemic Diseases Act; the figures shown are for the previous month and, for the period from the start of the year to the end of the previous month, the figures for the current year, the previous year, and the median for the last five years for comparison (Epidemiological Reporting System, as at 20 May 2026).

^a Diseases are assessed in accordance with the case definition. Diseases for which a case definition exists are shown, with the exception of transmissible spongiform encephalopathies. As a rule, confirmed and probable cases are counted. Changes may still occur due to late reporting or subsequent entries.

^b Bacterial and viral food poisoning, in accordance with the Epidemics Act.

^c Invasive bacterial disease, in accordance with the Epidemics Act.

^d Includes only cases of pneumonia.

^e Due to the lack of a case definition prior to 2025, only cases from 2025 onwards are shown; the median is also calculated only from 2025 onwards.

^f Mpox has been a notifiable disease since 2022; the median is calculated only for the years in which it is a notifiable disease.