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Lymphocytic choriomeningitis virus (LCMV) is an arenavirus closely related to Lassa virus, but unlike Junin virus it isn’t limited to South America: it’s found worldwide in house mice. Florian Krammer explains how people get infected, mostly by inhaling dust from dried mouse urine, droppings or saliva, and less often through bites, contaminated food or infected pets like hamsters.

Since the 1970s, cats in Sweden, and later in and around Vienna, have been falling ill with a mysterious brain inflammation known as staggering disease. Affected cats develop fever, behavioral changes, a staggering gait and often paralysis of the hind legs, and most have to be euthanized. For decades Borna disease virus was the main suspect, but metagenomics finally solved the case: in 2023, rustrela virus, a close relative of rubella virus, was detected in 27 out of 29 affected cats from Sweden, Germany and Austria.

Junin virus causes Argentine hemorrhagic fever, a disease with a case fatality rate of 20 to 30 percent. Florian Krammer explains why these New World arenaviruses are named after sand (they package host cell ribosomes that look like grains of sand under the electron microscope) and what makes their spike protein unusual: the signal peptide stays part of the glycoprotein complex, something found nowhere else in biology. The virus is carried by field mice, mainly the dryland vesper mouse, and people usually get infected by inhaling dust from dried urine and feces. That's why it mostly affects men working in...

Human metapneumovirus (HMPV) is one of the most common respiratory viruses there is, yet few people have heard of it. Florian Krammer explains why this relative of RSV is the second most common cause of respiratory illness in children under five and is behind 8 to 15 percent of pneumonia cases in that age group.

The 1918 Spanish flu was the deadliest influenza pandemic on record: between 20 and 100 million people died, from a world population of just 1.8 billion at the time. Florian Krammer explains why this H1N1 virus, with a case fatality rate of two to three percent, was so dangerous, where the misleading name comes from (Spain was neutral and had a free press when warring countries did not) and why mortality peaked among 20 to 40 year olds in a distinctive W-shaped curve.

Canine distemper virus is a paramyxovirus and a close relative of measles virus. Florian Krammer explains why the disease is so dangerous for unvaccinated dogs: in puppies between three and six months the case fatality rate is around 80 percent, and roughly 50 percent in adult dogs with no immunity.

Recorded in Sapporo, this episode is about a virus causing severe disease across Asia: SFTS virus, officially named Dabie bandavirus. It spreads mainly through the Asian longhorned tick, and in rare cases directly between people via blood and bodily fluids.

This time it's a herpes virus that almost all of us carry: human cytomegalovirus (CMV). Florian Krammer explains why this large DNA virus with over 200 proteins is so hard to pin down, how it deposits its genome as an episome inside immune cells and stays hidden there for decades.

This time it's a virus that has circulated in humans for millennia: mumps virus. Florian Krammer explains why this paramyxovirus is related to measles and the dangerous Nipah virus, how the infection unfolds, and why it's usually mild but can cause serious complications including inflammation of the testicles, brain, or pancreas.

A summer update with four current stories from the world of virology. First stop is Switzerland, where thousands of cows fell ill from a newly discovered orthobunyavirus of the Simbu group, closely related to Schmallenberg virus but with little risk to humans.