in the 20years since the first cases of aids were detected, scientists say they have learned more about this viral disease than any other.
yet peter piot, who directs the united nations aids program, and stefano vella of rome, president of the international aids society, and other experts say reviewing unanswered questions could prove useful as a measure of progress for aids and other diseases.
among the important broader scientific questions that remain：
why does aids predispose infected persons to certain types of cancer and infections？
a long-standing belief is that cancer cells constantly develop and are held in check by a healthy immune system. but aids has challenged that belief. people with aids are much more prone to certain cancers like non-hodgkins lymphomas and kaposis sarcoma , but not to breast, colon and lung, the most common cancers in the united states. this pattern suggests that an impaired immune system, at least the type that occurs in aids, does not allow common cancers to develop.
what route does hiv take after it enters the body to destroy the immune system？
when hiv is transmitted sexually, the virus must cross a tissue barrier to enter the body. how that happens is still unclear. the virus might invade directly or be carried by a series of different kinds of cells.
eventually hiv travels through lymph vessels to lymph nodes and the rest of the lymph system. but what is not known is how the virus proceeds to destroy the bodys cd-4cells that are needed to combat invading infectious agents.
how does hiv subvert the immune sys-tem？
although hiv kills the immune cells sent to kill the virus, there is widespread variation in the rate at which hiv infected people become ill with aids. so scientists ask：can the elements of the immune system responsible for that variability be identified？if so, can they be used to stop progression to aids in infected individuals and possibly prevent infection in the first place？
what is the most effective anti-hiv therapy？
in theory, early treatment should offer the best chance of preserving immune function. but the new drugs do not completely eliminate hiv from the body so the medicines, which can have dangerous side effects, will have to be taken for a lifetime and perhaps changed to combat resistance. the new policy is expected to recommend that treatment be deferred until there are signs the immune system is weakening.
is a vaccine possible？
there is little question that an effective vaccine is crucial to controlling the epidemic . yet only one has reached the stage of full testing, and there is wide controversy over the degree of protection it will provide. hiv strains that are transmitted in various areas of the world differ genetically. it is not known whether a vaccine derived from one type of hiv will confer protection against other types.
in the absence of a vaccine, how can hiv be stopped？
without more incisive , focused behavioral research, prevention messages alone will not stop the global epidemic.
the uniting of the world around the aids epidemic is without prior example. as the number of aids cases around the world rapidly increases, nations are showing great focus in battling this common enemy attacking rich and poor countries the same.
by 1989, almost every nation on earth had established a program educating its people about aids, according to jonathan mann, director of the world health organizations (who) international program on aids. at that time, 143 countries had reported one or more aids cases.
in addition to national aids programs, working together internationally has begun. through open exchanges of scientific facts as well as support of international organizations such as the world health organization, all nations can join efforts to fight against this life-threatening disease. according to who, this international effort has produced two critical developments: first, there is an amazing level of worldwide focus, using world scientists and international sharing of human and economic resources to fight aids. second, the work of governments, organizations, and businesses has been followed by the very high activity of people - as singles, families, and communities.
the influence of aids
the rise of acquired immune deficiency syndrome (aids) around the earth has represented a major challenge to medical progress both in developed and in less - developed countries. the past forty years saw great success in the control of spreading diseases and great strides toward achieving health for all by the year xx (a major who goal) through improved basic health care, food, cleanliness, and immunization(免疫) programs.
yet, because of its sudden start and rapid spread, aids could soon wipe out this progress. by the end of 1988, more than 130,000 cases of aids were reported, but, because of under reporting, there may actually be more than 350,000 cases. also, at least five million persons likely have the human immunodeficiency virus (hiv) (艾滋病病毒), which causes aids. that means as many as 400,000 new cases of aids could occur in the next few years - more than doubling the present total. caring for aids patients could seriously stress economic resources even in richer countries.
preventing one case of aids means preventing many future cases, while preventing a case of measles(麻疹) or malaria(疟疾) in africa would have little effect on its spreading, since those diseases are already common in many countries. resources devoted to aids testing, care, and education could also be used to battle other, more-known diseases in developing countries.
stopping the spread
aids spreads only in limited ways and can be prevented through informed and mature behavior. encouraging such behavior depends on understanding the different ways aids is spread around the world. aids spreads in three basic ways: first, through sexual intercourse(性交); second, through contact with diseased blood; and third from an hiv mother to her baby. the actual patterns of spreading of the aids virus change from culture to culture.
spreading of aids in north america, western europe, australia, new zealand and parts of latin america occurs most often among homosexual(同性恋) or bisexual(双性恋) men and intravenous (iv) (静脉内注射的) drug users(吸毒者), most often in city areas. heterosexual(异性之间的) spreading is low, but there is danger that the spread of aids from male(男性) iv-drug users to their female(女性) partners could increase the appearance of aids in the heterosexual population.
in sub-saharan africa and latin america, particularly the caribbean, most cases occur among heterosexuals, and spreading from mother-to-child is common. spreading through homosexual contact and iv-drug use almost does not exist.
in eastern europe, northern africa, the eastern mediterranean, asia, and most of the pacific, fewer cases of aids, usually among drug users, have been reported thus far. the who estimates that bangkok, thailand iv-drug users having the aids virus increased from less than 1 percent in august 1987 to 30 percent one year later.
reaching out
who believes that, as aids becomes more common, the disease promises to unite the world to a degree never seen before. in just two years, the international plan against aids has grown from ideas to practice, from speeches to action. who is certain that, together, we will triumph over aids rather than allow the disease and the fears, worries, and prejudices(偏见) which go with it to overpower us.
哈尔滨的立冬奇冷奇冷，滴水成冰。市民出门都裹得严严实实的，恨不得早些走进温暖的空调房。在这样寒冷的天气里，为了迎接世界艾滋病日的到来，我一个人站在冷清的中央大街上，向往来的路人发放预防艾滋病的宣传资料，为防艾事业做一份微薄的贡献。
无论人家背后如何指指点点，还是路人高枕无忧的态度，我都没有在意。我能做的，就是用自己的力量将防艾知识送入人们心中。
叔叔，后天就是世界艾滋病日了，请您支持一下中国的防艾事业，了解一下预防艾滋病的知识。阿姨，请您看一下，这是预防艾滋病的宣传资料，相信它一定能给你和你的家人送去一份健康。很多人都愉快地收下、道谢，似乎对我这个站在冷风中的孩子心生同情。寒冷的季节里，也不乏温暖的时刻。当我为一个孩子佩戴一枚红丝带时，一时感叹，人性中竟有这样美好的时刻。
在发放宣传资料时，一位穿着入时的女士接到传单，白了我一眼后将传单扔到地上。那一刻我很心痛，望着她的背影，我明白志愿者的道路绝非坦途，但这却更坚定了我的决心。
更恼人的是人们的世俗与偏见。我在附近的一家建筑工地发宣传资料，一群工人拿过传单后不屑地笑了起来：愿啥病啥病吧，我们干活哪能听你吹嘘？我急忙为他们讲解艾滋病的预防知识。然而，我的讲解也是徒劳的。我默然无语，心想：一个人没有预防知识，就等于没有健康，没有健康，又何谈劳动？
三个小时后，天色暗了下来，我已发了2300份宣传资料，还有些剩余，我便抓紧时间，趁着天黑之前发放完毕。这时，一位好心的老奶奶向我多要了几张，要为我减负。我说，自己的目的是让大家对艾滋病有所认识，完全出于自愿。四个小时内，我发放了宣传资料3000余份。天气虽然寒冷，但我的心滚烫、情火热。
防艾的脚步还在继续，不曾停滞，也永远不会停滞。
