Environmental Problems, Their Causes, and Sustainability 1

For example, the West Nile virus has spreadthroughout most of the lower 48 states but the chancesof being infected and killed by it is low (about 1 in2,500). In 2003, the flu killed more Americans in twodays than the West Nile virus killed during the entireyear.You can greatly reduce your chances of getting infectiousdiseases such as flu, the common cold, andSARS that spread from person to person by practicinggood old-fashioned hygiene. Wash your hands thoroughlyand often, and avoid touching your mouth,nose, and eyes.It is much harder to fight viral infections than infectionscaused by bacteria and protozoa. One problemis that most drugs that can kill a virus also harmthe cells of its host. Treating viral infections such ascolds, flu, and most mild coughs and sore throats withantibiotics is useless and increases genetic resistance indisease-causing bacteria.The best weapons against viruses are vaccines thatstimulate the body’s immune system to produce antibodiesto ward off viral infections. Immunization withvaccines has helped reduce the spread of viral diseasessuch as smallpox, polio, rabies, influenza, measles, andhepatitis B. But vaccines are not available for many viraldiseases.Case Study: How Serious Is the GlobalThreat from HIV and AIDS? A RapidlyGrowing Health ThreatThe spread of acquired immune deficiencysyndrome (AIDS), caused by HIV, is one of theworld’s most serious and rapidly growing healththreats.Sex can be hazardous to your health. Worldwide, almost400 million people are infected with a sexuallytransmitted disease (STD) each year. According to theU.S. Centers for Disease Control, almost one of everyfour Americans is walking around with an STD and atleast one in every three sexually active persons in theUnited States will contract an STD by age 24. STDs arerampant in high schools and colleges, where manystudents think, “It cannot happen to me.” Polls indicatethat 50–66% of sexually active students do not usecondoms and more than 40% have two or more sexpartners. Some STDs can cause infertility in men andwomen. Others can cause genital warts and genitalcancers or, in the case of HIV, eventually death.The global spread of acquired immune deficiencysyndrome (AIDS), caused by HIV, a serious and rapidlygrowing health threat. The virus itself is not deadly,but it kills immune cells and leaves the body defenselessagainst infectious bacteria and other viruses. Accordingto the WHO, by the beginning of 2004 some38 million people worldwide (96% of them in developingcountries, especially African countries south of theSahara Desert) were infected with HIV. Every dayabout 14,000 more people—most of them between theages of 15 and 24—get infected with HIV. According toU.S. Secretary of State Colin Powell, “AIDS is ...nowmore destructive than any army, any conflict, and anyweapon of mass destruction.”The news is going to get worse. Infection rates areincreasing rapidly in five countries—Nigeria, Ethiopia,Russia, Indonesia, Vietnam, India, and China—that togetherhave 40% of the world’s population.Within 7–10 years, at least half of those with HIVdevelop AIDS. This long incubation period means thatinfected people often spread the virus for several yearswithout knowing they are infected. So far, there is novaccine to prevent HIV and no cure for AIDS. Once you getAIDS, you will eventually die, although drugs may helpsome infected people live longer. However, only a tinyfraction of those suffering from AIDS can afford to usethese costly drugs.Between 1980 and 2004, more than 20 million people(460,000 in the United States) died of AIDS-relateddiseases. An estimated 280,000 of the roughly 900,000Americans infected with HIV do not know it and thereare about 42,000 new infections a year. In the UnitedStates, free or low-cost confidential testing for HIV exposureis available at many public health offices and atmany doctors’ offices. However, it takes a few weeksto 6 months or more before enough antibodies form inresponse to an HIV infection for any test to show thatthe virus is present. In addition, the conventional testsrequire several hours of lab time, often at another location,so that results may not be available for 1 to 2weeks. In 2003, the CDC began purchasing and pilottesting nationwide a new device called OraQuick. Itcan use a small amount of blood from a finger prick totest for HIV within 20 minutes. The accuracy rate is99.6%, roughly the same as more conventional bloodtests.AIDS has caused the life expectancy of 700 millionpeople living in sub-Saharan Africa to drop from 62to 47 years. The premature deaths of teachers, healthcare workers, and other young, productive adults insuch countries leads to diminished education andhealth care, decreased food production and economicdevelopment, and disintegrating families. Such deathsdrastically alter a country’s age structure diagram (Figure19-13, p. 424). AIDS has left 15 million orphans—roughly equal to every child under age 5 in America.Between 2004 and 2020, the WHO estimates 60million more deaths from AIDS and a death toll reachingas high as 5 million a year by 2020.According to the WHO, a global strategy to slowthe spread of AIDS should have five major priorities.First, shrink the number of people capable of infectingothers by quickly reducing the number of newinfections below the number of deaths. Second, concentrateon the groups in a society that are mosthttp://biology.brookscole.com/miller14423