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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 agriculture, with over 90 percent of the 300 to 500 annual cases occurring in rural areas.

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.

The final part of the summer series on vacation viruses is one you can catch without going anywhere: West Nile virus. Florian Krammer explains why this flavivirus is closely related to Japanese and St. Louis encephalitis virus, how it mysteriously showed up in New York in 1999 - most likely via mosquitoes on a container ship and spread across the entire US within a few years.

Part three of the summer series on viruses you can pick up on vacation. After Italy and Scandinavia, it's off to the tropics. Oropouche virus causes Oropouche fever and is spread not by mosquitoes but mainly by tiny midges — the same bloodsuckers that transmit bluetongue disease.

Part two of the summer series on viruses you might pick up on vacation — this time heading north. Sindbis virus is transmitted by ordinary Culex mosquitoes and causes a disease known variously as Pogosta disease, Ockelbo disease, or Karelian fever. Florian Krammer explains why it's closely related to chikungunya (you could call it the chikungunya of the north), how migratory birds spread it across Eurasia and Africa, and why most infections go unnoticed — there are 20 to 40 asymptomatic cases for every symptomatic one.

The first of a short series on viruses you might encounter while travelling: Pappataci fever is transmitted by sandflies and caused by viruses like Toscana virus, Naples virus, and Sicilian sandfly fever virus. Florian Krammer explains where the Italian name comes from, why these tiny 3-millimetre flies are poor fliers and therefore stay close to the ground, and why up to 25% of people in affected regions carry antibodies without ever having felt sick. Most infections are mild, but Toscana virus is neurotropic and can, in rare cases, cause meningitis or encephalitis. There's no vaccine and no treatment — insect repellent and long trousers are your only defence.

In this episode of viroLOGICAL, Florian Krammer explains the Marburg virus, a filovirus closely related to Ebola that causes severe hemorrhagic fever. He discusses how the virus is structured, how it enters cells, how it is transmitted from animals and between humans, and why infection is associated with very high mortality.