Word: infectivity
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...have sex with prostitutes. Infected male and female prostitutes are frequently also intravenous drug abusers; therefore, they may infect clients by sexual intercourse and other intravenous drug abusers by sharing their intravenous drug equipment. Female prostitutes also can infect their unborn babies...
Contaminated liquids that had been passed through porcelain filters designed to purify laboratory solutions and capable of blocking the passage of the smallest known bacteria were still able to infect both plants and test animals. However, careful microscopic scrutiny of the filtered liquids failed to reveal the "filterable agents" that caused the diseases. Also, unlike bacteria, these agents could apparently not be grown in culture dishes, where scientists hoped they might form colonies large enough to be seen with the naked eye. The source of such diseases as mumps, smallpox, yellow fever, rabies and dengue remained a mystery...
Although experimental work on mammals is proceeding slowly, Richard Mulligan, who has been practicing gene therapy on mice at the Whitehead Institute, is optimistic. "We are pretty damn close," he says. "We have retrovirus vectors that transfer efficiently. It looks like we can infect the ( appropriate types of cells reasonably safely." But, he concedes, he has not yet been able to induce the genes to "turn on" and order the cells to produce the missing proteins...
...cases of AIDS are really only the tragic, lethal tip of an epidemiological iceberg. Many more individuals, perhaps five to ten times as many, are currently suffering some effects of infection with the AIDS virus. Epidemiologists project that between one and two million individuals have been "exposed" to the virus, meaning they carry the virus and can infect others despite the fact that they currently are healthy...
Some viruses consist of a segment of double-stranded DNA surrounded by a protein skin. When they invade a cell, the DNA takes over the cell's genetic machinery and orders it to produce copies of the virus, which escape to infect other cells. The victim cell is often killed in the process. But the AIDS virus is a so-called retrovirus and contains single-stranded RNA. Alone, RNA lacks the ability to conquer cells, but retroviruses carry an enzyme called reverse transcriptase. When the AIDS virus invades an immune-system T cell, the enzyme enables the viral...