Now scientists are working on vaccines to fight the deadly bird flu H5N1. But these vaccines aren't easy to make. One reason is that the flu virus often mutates. So a vaccine that worked against the flu last year won't protect you very well this year.

Another problem is that it takes years of tests to make sure bird flu vaccines will work on humans without making them sick.

In 2005, a study began testing a possible bird flu vaccine on 450 people. The vaccine uses a type of bird flu that was found in Southeast Asia in 2004. Some of the early results are promising. But as of spring 2007, there is still no vaccine available for H5N1.

—When Birds Get Flu and Cows Go Mad!,
John DiConsiglio

Explain the challenges scientists face with mutating viruses and how they are trying to solve the problem.

The arctic national wildlife refuge is home to caribou, moose, musk oxen, wolves, foxes, grizzlies, polar bears and migratory birds. leaders in the oil industry believe the refuge is the perfect site for the “environmentally sensitive exploration” of oil. environmentalists are wondering: what will become of the wildlife? president george w. bush, oil-industry leaders and others believe that americans will benefit from the oil that lies under the snow-filled surface of the refuge. in their opinion, the oil will reduce high fuel prices and decrease our need for oil from other countries. i believe the cost of such drilling is too high. i agree with environmentalists who fear that drilling will disturb the migration of more than 130,000 caribou. each spring, the caribou travel 400 miles to give birth on the coastal plain. in this area of the refuge, there are fewer predators. in addition, experts say that the oil in the area adds up to less than a six-month supply. is such a small amount of oil worth the risk drilling poses to these animals? americans are the largest consumers of oil. instead of drilling for oil, we should decrease our need for foreign oil simply by using less. we must all work together to cut back on the oil we use in order to preserve the wildlife of the arctic national wildlife refuge. what type of argument is used in this paragraph? i believe the cost of such drilling is too high. i agree with environmentalists who fear that drilling will disturb the migration of more than 130,000 caribou. each spring, the caribou travel 400 miles to give birth on the coastal plain. in this area of the refuge, there are fewer predators. in addition, experts say that the oil in the area adds up to less than a six-month supply. is such a small amount of oil worth the risk drilling poses to these animals? a. appeal to emotion c. appeal to logic b. bandwagon d. none of the above select the best answer from the choices provided a b c d