No 44 - 2024
Pilot Project on Active Surveillance of Zoonotic Influenza in Denmark
Pilot Project on Active Surveillance of Zoonotic Influenza in Denmark
Statens Serum Institut, in collaboration with the University of Copenhagen, has launched a project on the active surveillance of zoonotic influenza among people with occupational exposure in Denmark.
General Information on Zoonotic Influenza
Influenza from birds and pigs can, in rare cases, infect humans, also known as zoonotic influenza. Zoonotic influenza can be a serious situation and requires attention in the healthcare system, as transmission to humans and between humans can potentially be the source of a new pandemic.
Avian influenza is seen in birds infected with a type of influenza A virus, which is related to the influenza virus that causes seasonal flu in humans. Avian influenza rarely infects humans, but it can happen through close contact with sick birds. There have been no reported cases of avian influenza in humans in Denmark.
Wild waterfowl are natural hosts for avian influenza viruses, and they can infect other wild birds as well as birds in poultry flocks. Since the autumn of 2020, several large outbreaks of highly pathogenic avian influenza have been observed in both wild and domestic birds in Denmark. There have also been cases of transmission to mammals, primarily terrestrial predators such as foxes, but also to seals. The situation is the same worldwide.
There are also influenza viruses among pigs, which in rare cases have been shown to infect humans. In Denmark, there have been two documented cases, both in 2021. The two cases were unrelated and did not lead to further transmission in the population.
Attention to Pandemic Risk
The European Centre for Disease Prevention and Control (ECDC) recommends that all countries increase their attention to zoonotic influenza (1,2). The concern regarding zoonotic influenza is that the virus changes through mutations and can then cause human-to-human transmission, potentially leading to a pandemic. It is therefore important to monitor possible transmission between animals and humans so that authorities can quickly respond with preventive measures.
Pilot Project on Active Surveillance of Zoonotic Influenza
Statens Serum Institut (SSI), in collaboration with the University of Copenhagen, has just launched a pilot project on the active surveillance of zoonotic influenza. The purpose of the project is to clarify the organization and framework for conducting active surveillance of people who may be exposed to zoonotic influenza through their occupation, and to investigate the prevalence of avian and swine influenza among people in contact with infected poultry or pigs. The project is part of a larger European surveillance project called “UNITED4Surveillance” (3).
The surveillance project targets people who have been exposed to infected/sick birds or pigs and who do not have symptoms or only have mild symptoms, such as a cold. The project involves screening in the form of self-swabbing among the exposed individuals. The swab samples are sent to SSI as urgent samples and tested with PCR, and participants are directly informed of the test results. The materials for the swab samples and shipping are provided free of charge by SSI to the participants by prior arrangement, with detailed instructions on the sampling procedure, data handling, etc.
Which Patients Should General Practitioners Be Aware Of?
General practitioners may come into contact with patients who have been exposed to avian influenza, swine influenza, or other zoonotic influenza. This may include participants in the above-described project on active surveillance of zoonotic influenza. It may also include employees of influenza-positive farms with poultry or pigs, personnel from the Emergency Management Agency or the Danish Veterinary and Food Administration who have recently been involved in the culling of an infected animal herd, or who have otherwise been particularly exposed to the virus, including contact with wild dead animals.
Procedures in Case of Suspected Zoonotic Influenza
General infection control precautions are used, supplemented with a mask and protective goggles or visor, gloves, and a fluid-resistant disposable gown with long sleeves (NIR General Practice, Danish language). It is recommended that the patient wears a mask, which the patient puts on themselves.
If the doctor finds it relevant to suspect zoonotic influenza (avian influenza, swine influenza, or other zoonotic influenza), a regular influenza swab sample is taken from the patient and sent to SSI.
At the same time, telephone contact should be made about the suspected case to the Danish Patient Safety Authority (STPS), and the case should also be reported in writing to both STPS and SSI via the electronic reporting system (for further information, please refer to the section entitled “Reporting Obligation”).
Patients who do not have a disease requiring hospitalization are advised to stay home until they are well and fever-free. If hospitalization is deemed necessary, the patient can be referred to the nearest infectious disease department with isolation in a single room (preferably a lock room ).
If a case of zoonotic influenza is detected in the pilot project, SSI’s virus watch will contact the patient’s general practitioner directly and provide further information.
Symptoms of Zoonotic Influenza in Humans
The incubation period in humans after infection with zoonotic influenza is typically 3-10 days. Reported symptoms in people with avian influenza from abroad have ranged from conjunctivitis and mild respiratory infections to severe lower respiratory infections with high mortality. In recent years, cases of avian influenza in humans in Europe, infected with the circulating variants of H5N1 highly pathogenic avian influenza, have been asymptomatic or with only mild symptoms. People with swine influenza have most often had mild illness, but in 2021 there was a severe case of swine influenza in Denmark.
Reporting Obligation
According to the notification regulation on the reporting of infectious diseases , influenza viruses of zoonotic origin, including avian influenza and swine influenza, are listed on List 1a. This means that in case of suspected or confirmed avian and swine influenza in humans, immediate telephone notification to the Danish Patient Safety Authority (STPS), written notification to both STPS and SSI, and laboratory notification to SSI must be made. Read more about the reporting system for individually notifiable diseases here.
Avian influenza has previously been described in EPI-NEWS 45-46b/2022, and the two described cases of swine influenza are described in SSI news in 2021 and 2022.
(G. Witteveen-Freidl, Department of Data Integration and Analysis, C.K. Hjulsager, R. Trebbien, U.V. Schneider, Department of Virus and Microbiological Special Diagnostics, S. K. Lefèvre, Secretariat for Infection Preparedness and One Health, A.C. Nordholm Breschel, T.R. Urth, L. S. Vestergaard, Department of Infectious Disease Epidemiology and Prevention)
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