Imagine being told that an infectious disease is caused by something that cannot be seen, cannot be grown by the methods available to you, and can pass through a filter designed to trap bacteria. At the end of the nineteenth century, this was almost unimaginable.
Yet this was the scientific mystery confronted by Friedrich August Johannes Loeffler. His investigations into diphtheria and, later, foot-and-mouth disease helped transform our understanding of infectious diseases. Loeffler became one of the pioneers of virology, while the research institute he established on the German island of Riems continues his scientific legacy more than a century later.
From Medicine to Microbiology
In 1879, Friedrich Loeffler was 27 years of age, when he had completed his medical studies, military service and began working as an assistant to Robert Koch, one of the founders of modern bacteriology. This brought him to the new world of laboratory medicine, where diseases were increasingly being linked to specific microorganisms.
Robert Koch discovered TB bacillus in 1882, and two years later in 1884, Fredrich Loeffler had identified bacterium responsible for diphtheria now known as Corynebacterium diphtheriae. In 1888, he became Professor of Hygiene at the University of Greifswald. He combined laboratory research with practical public health and was involved in improving sanitation and sewage systems in the city.
Existence of a virus is postulated
In the late 1890s, Loeffler turned his attention to foot-and-mouth disease, a highly contagious infection affecting cattle and other cloven-hoofed animals. Working with his colleague Paul Frosch, Loeffler filtered material from infected animals through filters capable of retaining bacteria. Yet the filtered material remained infectious.
The implication was revolutionary. Something smaller than bacteria was capable of causing disease. In 1898, Loeffler and Frosch described the infectious agent responsible for foot-and-mouth disease as a filterable agent capable of multiplication. Their experiments provided the first convincing evidence of an animal virus and became one of the foundational discoveries of modern virology.
From Discovery to an Island Laboratory
Loeffler’s work also demonstrated an important principle of scientific research: discovery needs infrastructure. To investigate foot-and-mouth disease safely and systematically, Loeffler established a dedicated research station on the Isle of Riems, near Greifswald. In 1910, the laboratory began its work and became the first research institution specifically established to study a viral disease of animals.
Friedrich-Loeffler-Institut (FLI)
Loeffler died in Berlin in 1915, aged 62. There is a striking continuity between Loeffler’s work and the mission of the modern Friedrich-Loeffler-Institut. The modern FLI conducts research into viral and bacterial diseases, emerging infections, epidemiology, zoonoses, and animal welfare. It also performs important diagnostic and reference functions for animal diseases in Germany and internationally.
But perhaps Loeffler’s greatest contribution was not simply discovering an organism. It was his willingness to challenge the assumptions of his time. He could not see the virus, but he could see its effects. The greatest discoveries sometimes begin when we realize that something exists—even though we cannot yet see it.
