Acute infection also means lots of viral shedding—by way of sneezing or coughing or vomiting or bleeding or diarrhea—which facilitates transmission to other victims. Such viruses try to outrace the immune system of each host, taking what they need and moving onward before a body’s defenses can defeat them. (Lentiviruses, including the HIVs, are exceptional here, following a different strategy.) Their fast replication and high rates of mutation supply them abundantly with genetic variation. Once an RNA virus lands in another host—maybe even another species of host—that abundant variation serves
...more
