Rubulavirus
If not vaccinated against mumps, susceptible individuals catch the disease by breathing around an infected person who has coughed or sneezed, releasing their contaminated saliva. Those who have had mumps are usually immune to future infections of the disease. Children have the highest risk of catching mumps, and it is rare for an adult to contract mumps. The incubation period for mumps can range from a couple weeks to a month, while the illness period is a few weeks. The swelling of the salivary glands is caused when the virus travels from the respiratory tract to the salivary glands and multiplies within the glands, causing the glands to swell.
Social history of viruses
Other, more ancient, viruses have been less of a threat. Herpes viruses first infected the ancestors of modern humans over 80 million years ago. Humans have developed a tolerance to these viruses, and most are infected with at least one species. Records of these milder virus infections are rare, but it is likely that early hominids suffered from colds, influenza and diarrhoea caused by viruses just as humans do today. More recently evolved viruses cause epidemics and pandemics – and it is these that history records. The influenza virus is one that seems to have crossed the species barrier from pigs to ducks and water fowl and hence to humans. It is possible that a fatal plague in the Middle East at the time of the late 18th Dynasty was associated with this transmission at Amarna.