While COVID-19, the novel coronavirus, dominates health news headlines, less exotic viral foes are still around: influenza, the rhinovirus, adenovirus, and respiratory syncytial virus behind the common cold, norovirus outbreaks aboard cruise ships, and always hepatitis and HIV.
What these viruses share is RNA as their genetic material, a nucleic acid less familiar than DNA. Among the RNA viruses are also West Nile, chikungunya, and those behind Ebola and Marburg hemorrhagic fevers, dengue, rabies, and yellow fever.
When science writer David Quammen made the media rounds recently to discuss COVID-19, he skipped the RNA part – "don't worry about that right now." But his excellent book Spillover: Animal Infections and the Next Human Pandemic, which charts the predictions of the current situation starting nearly a decade ago, details the significance of RNA viruses.
RNA is a nucleic acid like its cousin DNA, but has uracil in place of thymine as one of the four nitrogen-containing bases that carry each molecule's encrypted information. RNA's sugar – ribose – has an oxygen atom in a place that DNA's deoxyribose doesn't. DNA is the same in every cell of an individual, whereas shorter and shorter-lived RNA molecules carry out the specific DNA instructions that sculpt different cell types and functions.
The inability of RNA to repair itself, as DNA can, allows mutations to accrue in RNA viruses, enabling them to replicate wantonly and spread explosively. And our bodies help them. New viral particles spew from coughs and sneezes, are propelled in vomit, and ooze from blood and diarrhea, often before our immune systems begin to respond.
To continue reading, go to Genetic Literacy Project, where this post first appeared.