Confidence votes 175. Viruses can have either DNA or RNA (a virus will never have both at the same time, although some viruses can have each one separately at different stages of their life cycles). RNA viruses are much more common than DNA viruses. Nucleic Acid Amplification Testing for the Diagnosis of STDs The purpose of the nucleic acid amplification test (NAT or NAAT) is to find trace amounts of RNA or DNA in test samples.
SECTION 6. Man and Disease: The Black Death. Beginning in 1347 and continuing for a full five years, a devastating plague swept Europe, leaving in its wake more than twenty million people dead. This epidemic now known as the Black Death was an outbreak of bubonic plague which had begun somewhere in the heart of Asia and spread westward along trade routes.
The Black Death was an epidemic outbreak of bubonic plague in Europe around 1348 that killed between one-third and two-thirds of the population in less than five years. The epidemic spanned from China to England to North Africa, transmitted along the Silk Road and other trade routes. Worldwide, the plague may have killed one-quarter of all people. Repeated outbreaks continued in Europe into the 18th century. Some historians believe the drastic reduction in population hurried the end of feudalism by raising the value of labor and the power of workers, as seen in incidents like the 1381 Peasants Revolt in England.