Marilyn Roossinck: 101 viruses

Viruses are seldom considered beautiful, though visually, many are in fact stunning. While the sheer mention of them usually brings on vigilant hand-washing, some are actually beneficial to their hosts, and many are crucial to the health of our planet. Virus: An Illustrated Guide to 101 Incredible Microbes by Marilyn Roosinck offers an unprecedented look at 101 incredible microbes that infect all branches of life on Earth—from humans and other animals to insects, plants, fungi, and bacteria. Recently, Roosinck answered some questions about her gorgeously illustrated new book.

How did you come to study viruses?

MR: I started college at the Community College of Denver as an adult student (I was 22 years old), with a plan to go take two years of courses and then transfer to nursing school. I took a Microbiology course and when we studied bacterial viruses, I was totally smitten by how amazing viruses were, these very small and simple entities that could change everything! I ripped up my application to nursing school and instead transferred to the University of Colorado to pursue a degree in Biology. There were two biology departments at that time: Molecular, Cellular and Developmental Biology; and Environmental, Populational and Organismal Biology, so I did a double major and got a degree in both programs. As an undergraduate I did an independent study in a lab working on SV40, a model for many studies on mammalian viruses. I applied to the University of Colorado School of Medicine for graduate school, and I received my Ph.D. from that institution in 1986, doing a thesis on Hepatitis B virus.

Why 101 viruses?

MR: The original plan was to include 100 viruses, a nice round number and enough to allow a broad range of viruses, including those infecting all the major host groups, from bacteria to humans. Near press time the Zika virus outbreak in Brazil was attracting a lot of attention in the press, so we felt it was important to include Zika. We did not really want to remove one of the viruses that were already in the book, because these were chosen carefully, and each entry seemed important for the complete picture, so, borrowing from Hollywood, we decided 101 would also have a nice ring.

How did you choose the viruses described in the book?

MR: Making up the list of viruses to include in the book took a lot of thought. I wanted to cover every type of virus and every type of host. I also wanted to include some viruses that people would be very aware of, like influenza and Ebola. There are more human viruses in the book than those that infect any other host, because they are more thoroughly studied, and most of them are familiar to people. I also wanted to include viruses that were pathogens and those that were not. It may come as a surprise to many people that some viruses benefit their hosts, and several of these are included in the book too. I also got some help from colleagues. After making up the initial list I sent it out to a large number of virologists for comment, and I took these ideas into consideration too. Of course many people were sure that the virus they were studying was the most important virus and should be included, but I tried to ignore this as a basis for inclusion.

Do you have a favorite virus?

MR: It is hard to pick a favorite, there are so many viruses that have a fascinating natural history, or that can dramatically affect their hosts. One of my students in a Virus Ecology course that I teach at Penn State summed it up pretty well. I was introducing the topic of the how poliovirus became a serious problem in the 20th century due to changes in water treatment, and I said, “this is one of my favorite virus stories”. The student replied, “you say that about everything”.

What viruses do you work with in your own lab?

MR: I have spent about 30 years working on Cucumber mosaic virus, a serious crop pathogen that has the broadest host range of any known virus: it can infect 1200 different plant species! This means it has been very successful from an evolutionary point of view, so it is an excellent model for studying virus evolution. For the past decade I also have been studying viruses that infect fungi. My interest in these viruses began when we discovered a fungal virus in Yellowstone National Park that was beneficial to its host, allowing it to survive very high temperatures found in the geothermal areas of the park. This sparked an interest in viruses that help their hosts adapt to extreme environments, and we do a lot of work now on beneficial viruses in plants and fungi. We also are interested in the diversity of viruses, and we have done some studies looking for viruses in wild plants: there are a lot, and most of them are novel.

virus roossinck jacketMarilyn J. Roossinck is professor of virus ecology in the Department of Plant Pathology and Environmental Microbiology at Pennsylvania State University. She lives in Bellefonte, Pennsylvania. Roossinck is the author of Virus: An Illustrated Guide to 101 Incredible Microbes.