Thinking Scientifically

1. How can a virus have an enormous capsid, yet very few genes?

2. Suggest two ways that a virus can evade the host’s immune system.

3. Hantavirus pulmonary syndrome (HPS) is a flu-like illness that can kill a person within days. In 1993, a small outbreak occurred in the southwestern U.S. By studying the spread of other diseases, epidemiologists concluded that HPS was spread in rat excrement, and not from person to person. In larger outbreaks of hantavirus infection that occurred in Korea among U.S. military personnel during the war there in the 1950s, and again among soldiers in that nation in 1988, the condition was called Korean hemorrhagic fever. It had different symptoms – bleeding and kidney failure. Explain how the same virus at different times can spread in different ways and cause different symptoms.

4. Smallpox once killed millions of people, but thanks to widespread vaccination, it vanished by 1977. The virus, called variola, is kept as deep-frozen samples in two laboratories, although it is possible – some say likely – that many nations have kept samples for use as potential bioweapons. In 1993, researchers knew the genome sequence of variola, yet ironically, most doctors have never seen a case of smallpox. Using this information, provide arguments for and against destroying all remaining samples of this virus.

5. Since the 1970s, people have no longer been vaccinated against smallpox, because the disease has vanished. The vaccine also protected against a related viral illness, monkeypox. In the Democratic Republic of Congo, epidemiologists recorded 37 monkeypox cases between 1981 and 1986. But in 1996 and 1997, more than 92 cases were recorded. Explain why monkeypox might be on the rise.

Additional Questions and Terms

1. Describe nonbiological events that might have contributed to:

2. What are two biotechnologies that use viruses or their molecules? (Consult Chapters 12 and 13).

3. The reservoir of Ebola virus, which causes Ebola hemorrhagic fever in humans, isn’t known. However, laboratory-raised mice take up the virus in their cells, but do not develop symptoms. Using this information, suggest an experiment that could be conducted in the wild to look for the reservoir of Ebola virus.

4. Why are viruses useful as vectors in gene therapy?

5. The Hong Kong chicken flu only affected 18 people and new variant CJD hasn’t affected many more than that. Why, then, did the appearances of these disorders cause great concern in the medical community?