Influenza (synonyms: Influenca; influenza A virus infections; influenza virus; epidemic influenza; ICD-10-GM J09: influenza due to zoonotic or pandemic proven influenza virus; ICD-10-GM J11 influenza, viruses not proven; ICD-10-GM J11 influenza, viruses not proven) is an acute infectious disease caused by viruses. The term “influenza” is derived from Latin and means “to creep in.” Influenza is not the same as the normal cold, the so-called flu-like infection. Classification according to ICD-10-GM:
- ICD-10-GM J09: Influenza caused by zoonotic or pandemic proven influenza viruses.
- ICD-10-GM J11 Influenza, viruses not detected.
- ICD-10-GM J10.0 Influenza with pneumonia, seasonal influenza viruses detected.
- ICD-10-GM J10.1 Influenza with other respiratory tract manifestations, seasonal influenza viruses detected
- ICD-10-GM J10.8 Influenza with other manifestations, seasonal influenza virus detected
- ICD-10-GM J11 Influenza, viruses not detected.
- U69.20! : Influenza A/H1N1 pandemic 2009 [swine flu].
- U69.21! : Influenza A/H5N1 epidemic [avian flu].
One can distinguish a seasonal and a pandemic influenza. Furthermore, there is the new flu (called swine flu).
Seasonal influenza
Influenza A virus infection is the cause of several thousand deaths in Germany each year. Typical of influenza is the occurrence of epidemics at 2-3-year intervals. This can be explained by genome changes of the influenza A virus due to constant point mutations, which is called antigenic drift. This affects all three forms of influenza (A, B, C). Pandemics (transnational epidemics occurring worldwide) are also possible. One of the largest influenza pandemics was the Spanish flu of 1918/19, which killed about 50 million people. The contagiousness of the pathogen is high. Seasonal accumulation of the disease: Seasonal influenza occurs more frequently in the winter months, in the period from December to April. Transmission of the pathogen (route of infection) occurs primarily via droplets that are produced when coughing and sneezing and are absorbed by the other person via the mucous membranes of the nose, mouth and possibly the eye (droplet infection) or aerogenically (through droplet nuclei containing the pathogen (aerosols) in the exhaled air). In addition, transmission is also possible via hands and surfaces contaminated by virus-containing secretions if the hand subsequently has contact with the nose and mouth.A study to elucidate the routes of transmission of the influenza virus was able to demonstrate that even in the exhaled air of influenza-infected persons, collected without coughing or sneezing, virus quantities sufficient for infection could be detected. Human-to-human transmission: Yes. The incubation period (time from infection to onset of illness) is 1-8 days (usually 1-3 days). Even during the incubation period, the patient is already infectious! About a week after the appearance of the first symptoms, there is no longer any danger of infection. The duration of the disease is usually 5-7 days, but can be much longer depending on complications and risk factors. The incidence (frequency of new cases) is about 50 cases per 100,000 inhabitants per year (in Germany). Course and prognosis: Complications from influenza can occur at any age, but predominantly affect older people (> 60 years) and those with underlying chronic diseases. The lethality (mortality related to the total number of people with the disease) is 0.2%. The majority (approximately 87%) of those who die are older than 60 years. Note: Seasonal influenza has the greatest burden of disease of all infectious diseases. Vaccination: Vaccination against influenza is available. In Germany, direct detection of the pathogen is reportable under the Infection Protection Act (IfSG) if the detection indicates an acute infection.
New influenza (called swine flu)
The disease is caused by the H1N1/2009 virus. Human-to-human transmission: Yes. The incubation period is usually 3-4 days (range 1 to 7 days). Course and prognosis: The course of the new flu is currently mild. However, younger people are becoming increasingly ill. In addition, the virus is more contagious than the other types of flu.The lethality (mortality in relation to the total number of people who contract the disease) is 0.02-0.04%. Vaccination: vaccination against swine flu is available.
Pandemic influenza (avian influenza)
Pandemic influenza describes the so-called “bird flu” (avian influenza; primarily the H5N1 subtype). Pathogen reservoirs are waterfowl. Since 2003, pathogens of the subtype influenza A(H5N1) have spread in wild birds and domestic poultry (chickens) in more than 60 countries on 3 continents. The viruses are now also circulating in various mammalian hosts and crossing species boundaries via animal feeding behavior. Transmission of the pathogen can occur primarily through direct contact with infected poultry. The incubation period is usually 2-5 days, unlike seasonal influenza. The lethality (mortality related to the total number of people infected with the disease) is more than 50% in treated patients. In the case of avian influenza, even the suspicion is notifiable according to the IfSG; in the case of seasonal influenza, only the direct detection of the virus is. Notice. Since March 2013, a new avian influenza has appeared in China (H7N9 virus). It can spread directly among mammals (human-to-human transmission is likely), and this even aerogenically (through the air).
