Abstract: Medical entomologist who discovered the bacteria that causes Lyme disease. Born on June 27, 1925, in Basel, Switzerland, he died from complications of Parkinson's disease on Nov 17, 2014, in Hamilton, MT, USA, aged 89 years.In 1981, the New York State Department of Health was investigating suspected cases of Rocky Mountain spotted fever on Long Island and sent deer ticks to Willy Burgdorfer at the Rocky Mountain Laboratories in Montana, USA, for examination. Like he had done thousands of times before, Burgdorfer dissected the ticks and stained cells from the gut, looking for the short, rod-like rickettsia bacteria that causes the disease. Instead, he saw long, slender, coiled bacteria that he'd first studied 30 years earlier as a graduate student. “Once my eyes focused on these long snake-like organisms, I recognized what I had seen a million times before: spirochetes”, he recalled in an interview in 2001.Right away, Burgdorfer speculated the spirochetes were the cause of Lyme disease, which was first recognised in children in Connecticut during the 1970s and, at the time of Burgdorfer's discovery, confounded scientists. Deer ticks were believed to carry the disease but the agent that caused it was unknown. Within hours of spotting the spirochetes, Burgdorfer phoned colleagues to get serum samples collected from patients with the disease; his suspicion was soon confirmed when the samples reacted with the spirochetes. He and his colleagues published the discovery in Science in 1982. “It was a big breakthrough—now we had an organism to deal with”, says Durland Fish, a professor of epidemiology at Yale University who specialises in vector-borne diseases. Until then, Lyme disease was treated empirically with antibiotics. “Figuring out the bacterial agent opened up areas of treatment, lab diagnostic testing, and the development of a vaccine”, says Tom Schwan, a senior investigator at Rocky Mountain Laboratories who was a mentee of Burgdorfer. The bacteria was named Borrelia burgdorferi in honour of Burgdorfer's discovery.A self-described “tick surgeon”, Burgdorfer dissected tens of thousands of the arthropods during his career. As a graduate student in Switzerland he studied how ticks transmitted spirochetes to patients with relapsing fever; as a scientist at the US National Institutes of Health Rocky Mountain Laboratories he spent decades analysing ticks from around the USA for the rickettsia bacteria that causes Rocky Mountain spotted fever. “If you have a tick on your head and give me the tick in half an hour I can tell you whether or not you have to watch out for clinical manifestations that could be spotted fever or something else”, he said in 2001. Burgdorfer helped to describe the geography of Rocky Mountain spotted fever and of infected ticks and, in turn, educated the general public and physicians about prevention of the disease. He maintained that education was the best way to prevent a tick-borne disease, including Lyme disease. Each year, about 300 000 people are diagnosed with Lyme disease in the USA, according to the US Centers for Disease Control and Prevention. Antibiotics are effective in treating the disease, although in 10–20% of patients symptoms persist.Burgdorfer received his undergraduate degree and his doctorate degree in parasitology and tropical bacteriology from the University of Basel. In 1951, he accepted a fellowship at the Rocky Mountain Laboratory, which was established in the early 1900s to study Rocky Mountain spotted fever in Montana's Bitterroot Valley. For the next 35 years, he studied that disease, Colorado tick fever virus, snowshoe hare virus, plague, relapsing fevers, and other diseases carried by arthropods. He observed that one side of the Bitterroot Valley had more ticks infected with a disease-causing rickettsial strain than the other side, and described how the presence of another bacteria in the ticks there prevented them from being infected with spotted fever. The mechanism of this bacterial inhibition is still unknown.The recipient of many awards for his work, including a Guggenheim Fellowship and the Bristol Award from the Infectious Diseases Society of America, Burgdorfer retired in 1986 and became a scientist emeritus, allowing him to continue his research. “He was one of the last real gentleman scientists”, says Fish. “He shared his wealth of knowledge with anyone.” Burgdorfer's first wife Dale, a secretary at the laboratory who also helped to prepare yellow fever vaccine, died in 2005. He is survived by his sons from their marriage, Bill and Carl; his wife, Lois; and a brother, Karl. Medical entomologist who discovered the bacteria that causes Lyme disease. Born on June 27, 1925, in Basel, Switzerland, he died from complications of Parkinson's disease on Nov 17, 2014, in Hamilton, MT, USA, aged 89 years. In 1981, the New York State Department of Health was investigating suspected cases of Rocky Mountain spotted fever on Long Island and sent deer ticks to Willy Burgdorfer at the Rocky Mountain Laboratories in Montana, USA, for examination. Like he had done thousands of times before, Burgdorfer dissected the ticks and stained cells from the gut, looking for the short, rod-like rickettsia bacteria that causes the disease. Instead, he saw long, slender, coiled bacteria that he'd first studied 30 years earlier as a graduate student. “Once my eyes focused on these long snake-like organisms, I recognized what I had seen a million times before: spirochetes”, he recalled in an interview in 2001. Right away, Burgdorfer speculated the spirochetes were the cause of Lyme disease, which was first recognised in children in Connecticut during the 1970s and, at the time of Burgdorfer's discovery, confounded scientists. Deer ticks were believed to carry the disease but the agent that caused it was unknown. Within hours of spotting the spirochetes, Burgdorfer phoned colleagues to get serum samples collected from patients with the disease; his suspicion was soon confirmed when the samples reacted with the spirochetes. He and his colleagues published the discovery in Science in 1982. “It was a big breakthrough—now we had an organism to deal with”, says Durland Fish, a professor of epidemiology at Yale University who specialises in vector-borne diseases. Until then, Lyme disease was treated empirically with antibiotics. “Figuring out the bacterial agent opened up areas of treatment, lab diagnostic testing, and the development of a vaccine”, says Tom Schwan, a senior investigator at Rocky Mountain Laboratories who was a mentee of Burgdorfer. The bacteria was named Borrelia burgdorferi in honour of Burgdorfer's discovery. A self-described “tick surgeon”, Burgdorfer dissected tens of thousands of the arthropods during his career. As a graduate student in Switzerland he studied how ticks transmitted spirochetes to patients with relapsing fever; as a scientist at the US National Institutes of Health Rocky Mountain Laboratories he spent decades analysing ticks from around the USA for the rickettsia bacteria that causes Rocky Mountain spotted fever. “If you have a tick on your head and give me the tick in half an hour I can tell you whether or not you have to watch out for clinical manifestations that could be spotted fever or something else”, he said in 2001. Burgdorfer helped to describe the geography of Rocky Mountain spotted fever and of infected ticks and, in turn, educated the general public and physicians about prevention of the disease. He maintained that education was the best way to prevent a tick-borne disease, including Lyme disease. Each year, about 300 000 people are diagnosed with Lyme disease in the USA, according to the US Centers for Disease Control and Prevention. Antibiotics are effective in treating the disease, although in 10–20% of patients symptoms persist. Burgdorfer received his undergraduate degree and his doctorate degree in parasitology and tropical bacteriology from the University of Basel. In 1951, he accepted a fellowship at the Rocky Mountain Laboratory, which was established in the early 1900s to study Rocky Mountain spotted fever in Montana's Bitterroot Valley. For the next 35 years, he studied that disease, Colorado tick fever virus, snowshoe hare virus, plague, relapsing fevers, and other diseases carried by arthropods. He observed that one side of the Bitterroot Valley had more ticks infected with a disease-causing rickettsial strain than the other side, and described how the presence of another bacteria in the ticks there prevented them from being infected with spotted fever. The mechanism of this bacterial inhibition is still unknown. The recipient of many awards for his work, including a Guggenheim Fellowship and the Bristol Award from the Infectious Diseases Society of America, Burgdorfer retired in 1986 and became a scientist emeritus, allowing him to continue his research. “He was one of the last real gentleman scientists”, says Fish. “He shared his wealth of knowledge with anyone.” Burgdorfer's first wife Dale, a secretary at the laboratory who also helped to prepare yellow fever vaccine, died in 2005. He is survived by his sons from their marriage, Bill and Carl; his wife, Lois; and a brother, Karl.