Influenza

The Infection Biology Unit investigates influenza viruses at the German Primate Center.

The viral flu, also called influenza, is an infectious disease that annually infects about 10 to 20 per cent of the world population according to estimates of the World Health Organization (WHO). Every year, about 250,000 to 500,000 people die from it. Therewith, the influenza is significantly more dangerous than the common cold, which is often also called "flu".

Even though the symptoms of an influenza infection, like cough, fever, headache, sore throat, and rheumatic pains are similar to those of a cold, they represent to different diseases. Influenza is especially threatening for people with a weak immune system like elderly, young children or pregnant women. The German Federal Ministry of Health therefore recommends a number of preventive actions like vaccination and sanitation. There is also a national pandemic plan, which shall support the containment in case of a large wave of influenza.

A poster advising to get vaccination against influenza viruses. Image: Federal Center for Health Education

Influenza can be caused by three different viral types (A, B, and C) of which the influenza C type viruses are the less common agents.

An infection can be transmitted via contact with virus-containing droplets that result from sneezing or via contact with contaminated surfaces. Influenza viruses are inured to dryness and cold, and an infected person is contaminous for about four to five days. The diseases lasts for about five to seven days.

Waves of influenza regularly occur worldwide and in Europe especially during the winter months. Non-seasonal, local influenza outbreaks occur time and time again. Influenza viruses are hard to fight because they continuously change their properties. Therefore, new vaccines have to be developed every year, and risk groups are recommended to get an annual vaccination

Transmission from animal to human

Influenza viruses can also be transmitted from animal to human. Examples for this are the avian flu and the swine flu. The influenza virus H5N1, known as the avian flu, hits the headlines repeatedly for causing deaths since 2003. In April 2013 a new form of the avian flu, the H7N9, was verified in human patients in China. The swine flu, caused by the influenza A virus subtype H1N1, gave rise to a worldwide pandemia from April 2009 to August 2010.

Influenza A virus H1N1 — The influenza virus H1N1 in an electron microscopy magnification. Image: Norbert Bannert, Lars Möller/RKI

The Infection Biology Unit investigates at the DPZ how influenza viruses enter host cells. A focus of the work is the viral protein "hemagglutinin". The protein mediates the binding of the influenza virus to the host cell. When the virus is attached to the cell, hemagglutinin fuses the viral envelope to the cell membrane and thus allows the infiltration of the viral genetic information into the cell. To make this work, hemagglutinin has to be split and activated first. This happens through host cell enzymes, so called proteases. But which proteases are involved in this process and how it works is unknown so far and research at the DPZ focuses on this. At the same time the scientists of the Infection Biology Unit search for inhibitors, which block the hemagglutinin activation and therefore might hinder an influenza infection. The research on influenza at the DPZ is mainly performed on cell cultures.