In the last few years, we have witnessed a significant increase in weather-related disasters throughout the world. Droughts, wildfires, heat waves, hurricanes, and floods have all become more extreme. These are largely driven by increases in global temperature, which is caused by the huge amount of carbon dioxide (CO₂) that humans have released into the atmosphere.

In a 2002 essay, Dutch atmospheric chemist Paul Crutzen popularized the name “Anthropocene” for the current geologic time period. Though unofficial, it is widely accepted by scientists because of how drastically humans have altered the Earth. We have cleared forests, built cities, diverted waterways, replaced wild animals with domestic ones, created billions of tons of plastic waste, and perhaps most significantly, changed the climate.

I’ve mentioned in previous posts that giant viruses are an unusual group of viruses because they share some characteristics with bacteria. In this post, I will discuss some other viruses and infectious agents that also bend the rules. These include viroids, satellite viruses, and prions.

When we think of viruses today, we imagine tiny disease-causing invaders. The COVID-19 pandemic has brought viruses to the forefront of people’s minds, and we are constantly looking for ways to avoid, kill, and fight off viruses. Many well-known viruses do cause diseases in animals and plants, but a far greater number of viruses are necessary for the survival of cellular life, either for an individual species or an entire ecosystem. Viruses help maintain the health of the oceans, and still others can help our immune systems develop.

The 2010 killing of trainer Dawn Brancheau at SeaWorld Orlando came as a shock to the world. Brancheau was an experienced trainer who had worked with orcas for 15 years. The day of her death, she was performing a show with Tilikum, a large male killer whale, who drowned her. According to SeaWorld executives, orcas and other performing animals, such as dolphins and sea lions, live good lives in captivity with medical care and loving trainers. The death of Dawn Brancheau was a freak accident due to trainer error, they said. But it wasn’t.