Viruses+MC

7.1 (p.122-124) and Avian Flu p. 125

1. Why are viruses not exactly living or nonliving? - Outside a host, viruses are essentially chemicals that can be stored on a shelf. But when the opportunity arises, viruses replicate inside the cells, and during this period of time, they clearly appear to be alive. 2. Give some examples of diseases caused by viruses. -colds, flu, measles, chicken pox, polio, rabies, AIDS, genital warts, and genital herpes. Viruses are acellular –-not composed of cells. They obligate parasites and they do not live independently. 3. What is the basic structure of a virus? (The two parts and their function). - It has an outer capsid composed of protein subunits and an inner core of nucleic acid composed of either DNA or RNA. A virus itself carries the genetic information needed to reproduce itself. A virus may also contain various enzymes that help it reproduce. 4. Why are viruses like microscopic pirates? -because they are commandeering the metabolic machinery of a host cell. Viruses gain entry into and are specific to a particular host cell because portions of the virus adhere in a lock-and-key manner with a receptor on the host cells outer surface. The viral nucleic acid then enters the cell. Then it codes for the protein units in the capsid. 5. Why are viruses considered parasites? -because they are acellular, not composed of cells. 6. Why are viruses considered OBLIGATE parasites? - because they do not live independently 7. Why do viruses ALWAYS cause disease? -because virus particles are about 4 times smaller than a bacterium, which is about a hundred times smaller than a eukaryotic cell. 8. How do viruses "emerge" and "spread" each year? Give examples. -A virus emerges by being transported from one location to another where it has not been before.Flu strains move from Southeast Asia to the United States each year. The West Nile virus is making headlines because it has changed its range, being transported into the United States and taking hold in bird and mosquito populations. SARS was clearly transported from Southeast Asia to Toronto, Canada. Disease spread by insects and a it can emerge when a mutation allows a virus to use a new and different insect vector. Viruses can emerge because of the inability of the immune system to recognize a change in the virus that allows it to cause disease. 9. What is a virus vector? Give examples. -A virus vector are insects that carry disease from an infected individual to a healthy individual. If a virus transmitted by a more common species of mosquito can now be transmitted by a more common species, a disease could spread more easily. 10. What is the relationship of bird flu to birds? -Birds can become infected by coming into contact with the saliva, feces, or mucus of another infected bird. 11. How does bird flu infect humans? - Infected humans die or the human flu could end up swap and mixing genes with the avian bird flu which is fatal, deathly, infectious, and easily transmitted. 12. What is a pandemic? - An increase in the occurrence of a disease within a large population and geographically widespread population. 13. Why is there fear that bird flu could cause a pandemic? - A new hybrid virus could form from the merging of the other two. This new virus could highly be infectious, fatal, and easily transmitted from person to person. Rapid travel between countries would enable people to spread the flu virus across the globe at an unprecedented rate, potentially triggering a global pandemic. When a human infected with the human flu and then comes into contact with the avian flu, the two viruses could meet in the person’s body and swap genes with each other, or if the two viruses infect a different host species and swap their genes in that host species. 14. What action can we take to prevent a bird flu pandemic? - There are no vaccinations that work against the bird flu. Several drugs are being trialed and have produced mixed results. Scientists are racing to find potential vaccination but face the challenge of a virus that is constantly evolving. Government have begun programs to remove the infected and potentially infected birds. Millions of domesticated birds have been killed in an attempt to control the spread of the virus.