RT-PCR, however, the RNA strand is first reverse transcribed into its DNA complement (complementary DNA, or cDNA) using the enzyme reverse transcriptase, and the resulting cDNA is amplified using traditional or real-time PCR. Reverse transcription PCR is not to be confused with real-time polymerase chain reaction (Q-PCR/qRT-PCR), which is also sometimes (incorrectly) abbreviated as RT-PCR (http://en.wikipedia.org/wiki/Reverse_transcription_polymerase_chain_reaction, accessed November 6, 2009).

RNA virus: A virus that contains ribonucleic acid (RNA) as its genetic material.

Salvage therapy: A final treatment for people who are nonresponsive to or cannot tolerate other available therapies for a particular condition and whose prognosis is often poor (http://www.medterms.com/script/main/art.asp?articlekey=9380, accessed December 17, 2009).

Serological: The use of immune serum in any of a number of tests (agglutination, precipitation, enzyme-linked immunosorbent assay, etc.) to measure the response (antibody titer) to infectious disease; the use of serological reactions to detect antigen.

Strain: A subgrouping of organisms within a species, characterized by some particular quality.

Surveillance: The continuing scrutiny of all aspects of occurrence and spread of a disease that is pertinent to effective control.

Vaccine: A biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe. The agent stimulates the body’s immune system to recognize the agent as foreign, destroy it, and “remember” it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters.

Virulence: The degree of pathogenicity of an organism as evidenced by the severity of resulting disease and the organism’s ability to invade the host tissues.

Virulence factors: The properties (i.e., gene products) that enable a microorganism to establish itself on or within a host of a particular species and enhance its potential to cause disease.

Virus: A small infectious agent that can only replicate inside the cells of another organism. Viruses are too small to be seen directly with a light microscope.