LONDON -- Some opt for the romantic approach. In France, real "French letters" are handed out by student groups, each envelope marked with winged cupids and a valentine heart, each containing a condom.

Some think fear works best. Government pamphlets in India show a pair of grizzled death's hands reaching down from the sky. On the Caribbean island of Dominica, posters do not mince words. "New. Deadly. No cure. Big trouble." In Britain, subway stations are papered with shocking photographs of dirty, dripping syringes and needles.

In Denmark, the emphasis is on informative humor. Buses in Copenhagen sport 20-foot-long painted condoms, with the message "Vive la petite difference." Posters directed at Australian aboriginals use an illustrated character named "Condoman" to tout the benefits of using "Frenchies."

Others find the indirect approach more effective. Advertisements in Uganda warn against "Slim disease" and admonish citizens to "Obey God's law and live long."

While the method and message may differ, the goal throughout the world is the same -- to prevent the spread of acquired immune deficiency syndrome, AIDS. The depth of international concern about the disease was illustrated last week in London, when health ministers and other high-level officials from nearly 150 countries, representing 95 percent of the world's population, showed up for a conference on the subject.

The London summit, jointly sponsored and paid for by the United Nations World Health Organization (WHO) and the British government, was not the first international gathering on AIDS. But it marked the first time so many of the world's nations had come together to discuss the disease on a political, rather than scientific or medical, level.

During three days of meetings, delegations recounted the spread of AIDS in their own countries and showed off their anti-AIDS propaganda and services. While a few, mostly in Asia and the Middle East, proudly declared themselves AIDS-free, others issued horrifying accounts of the infection and deaths their nations had suffered. Some Third World countries pleaded poignantly for access to the fruits of AIDS research being conducted in other lands.

Some nations blamed others for the spread of the disease; others angrily rejected blame.

At the end, they all agreed to a declaration recognizing that none is to blame and all are at risk. In the absence of a vaccine or a cure, they acknowledged that information and education to persuade people to stay away from the practices that spread the disease are the only way of curbing it.

They pledged their governments to expanding nationwide educational programs, to developing national anti-AIDS strategies that are coordinated with the WHO global strategy and to providing social services to aid high-risk population groups like homosexuals, prostitutes and intravenous drug users before they become infected. They recognized that discrimination against any segment of society, and mandatory testing of any group, were largely ineffective in preventing AIDS, and promised to promote tolerance around the world.

Whether these words are translated into deeds remains to be seen. As some observers pointed out, any declaration that can encompass such widely different views as those of the Vatican, the Soviet Union and the United States, as well as Israeli and Arab governments and much of the Third World on a subject like AIDS cannot be too precise or binding.

Many of the promises made in the declaration already are broken daily in countries around the world. Chinese epidemiologist Wang Shusheng noted that "Chinese law and traditional moral values prohibit homosexuality, sexual promiscuity and the abuse of drug injection." Therefore, he said, none of those problems, or AIDS, existed in his country.

The British government was repeatedly challenged at the conference on its assertion that it did not attempt to bar people it determined were in "suspect" categories from entering the country.

The U.S. delegation, headed by Assistant Health Secretary Robert E. Windom, reacted testily to suggestions that despite a newly instituted education program, its government has so far failed to develop a nationwide anti-AIDS strategy of the kind it has urged, and even helped finance, in developing countries.

Bulgaria, Argentina, South Africa and China are among the nations that practice some degree of mandatory AIDS testing, and Japan and India have talked about doing the same. Thailand has a law excluding infected aliens from entering the country and deporting those already inside. Iraq requires a screening certificate for entry, and Belgium is considering demanding the same for visitors from some African countries.

But despite remaining differences of assessment and approach, Dr. Jonathan Mann, director of the WHO Special Program on AIDS (SPA), pronounced the summit a major success. Health ministers from around the world, he said, will have taken home a new sense of the global nature of AIDS, better ideas on how to combat its spread, and stiffer political backbone to press those governments that have been lax in attacking the disease.

As recently as a year ago, Mann insisted, it would have been inconceivable that such a gathering would draw such high attendance, and hold such relatively open discussions about the highly sensitive issues surrounding what is now called the AIDS "pandemic" -- a worldwide epidemic.

Tracing the spread of the human immunodeficiency virus (HIV), Mann described it as "old, but not ancient, of unknown geographical origin." Its spread, he said, appears to have begun in the mid-1970s, but it was not until 1981 that the disease it causes, AIDS, was first recognized. Several more years passed before it was identified as a global phenomenon, with infection and disease discovered on all continents.

WHO now believes that between 5 million and 10 million people worldwide have become infected with HIV and that at least 150,000 people have developed AIDS. From now on, Mann said, the disease will continue to grow exponentially, with an additional 150,000 cases in 1988. Because the incubation period for the disease can be as long as 10 years, nearly everyone who will develop AIDS this year already has been infected.

The well-documented ways in which the infection is known to spread have been both the blessing and the curse of efforts to curtail it.

Since the virus is transmitted through certain bodily fluids -- primarily blood, semen and sexual secretions -- the relative blessing of AIDS, if such a term can be used, is that its spread can be contained by preventing the fluids of an infected person from coming into contact with someone who is virus-free. Persuading people to avoid promiscuous or casual sex with unknown partners, promoting the use of condoms, screening blood donations, discouraging drug abuse and the use of unsterilized injection equipment all are recognized ways of containing the rate of HIV transmission.

At the same time, however, the activities that are known to risk HIV infection are those that go not only to the heart of human privacy but often to the core of national identity.

Promiscuous sex, homosexuality and bisexuality, drug abuse and unclean health practices are not openly admitted in some countries and are outlawed in others. This makes it difficult to acknowledge the presence of the disease or discuss ways to reduce the risks of spreading AIDS.

Even in the most theoretically open of societies, dealing with such issues is not always easy. According to Steve Rabin of Ogilvy and Mather, the advertising firm hired by the U.S. federal government to develop its AIDS information program, "we can't even get the word 'condom' on two of our three major television networks." Only NBC, he said, has allowed prime-time broadcast of the campaign's public service announcements using the word.

At the same time, Rabin said, the campaign has found it difficult to persuade the American media to stop using vague terminology like "intimate sexual contact" in referring to particularly dangerous sex practices instead of using more explicit phraseology, such as anal intercourse.

Kuwaiti Public Health Minister Dr. Abdul Rahman, whose country has reported no cases of AIDS, spoke about the problems faced by traditionally conservative societies. "Despite the availability of information worldwide, in developing its educational programs, Kuwait cannot embrace the open and explicit approach adopted by Western countries with more heterogenous social structures," Rahman said.

"It should also be pointed out that in a country such as Kuwait," he said, "a closely knit family structure which forms the basis of an Islamic society may jeopardize accurate reporting by families and family doctors of the incidence of AIDS cases . . . It will be difficult to maintain the anonymity of, and avoid discrimination against, AIDS victims and their families in a society where practically everyone knows everyone else" among the 2 million population.

Every society, and different groups within nations, has been tempted to seek the reassurance of immunity against AIDS through scapegoating other people and isolation, according to the WHO's Mann. There was a strong initial tendency that still exists in many areas to believe the disease might be limited to certain groups or nations. Some whites in industrialized countries blame Africa; Soviet and Chinese officials blame "Western decadence"; heterosexuals blame homosexuals.

"There is no country in the world where the battle against discrimination has been won," Mann said. Even what he called the "political act" of reporting the incidence of AIDS cases to the WHO is a difficult step for some countries that do not want to acknowledge the presence of the disease in their culture. Worldwide, the numbers of cases reported to the WHO are believed to be grossly underestimated.

Yet it is a step that 132 nations have now taken, compared to only 31 four years ago.

One of the purposes of the London summit was to paint a broad picture of the epidemiology of AIDS to demonstrate that no single region or group of people can be blamed for starting it or spreading it -- and to prove that no country is exempt from the peril it poses.

Although the HIV epidemic exists worldwide, the spread of AIDS is not the same everywhere, and the WHO divides the globe into three distinct epidemiological patterns that are expected to merge with time.

Pattern I countries, where the bulk of reported AIDS cases have occurred, include Western Europe, North America and some areas of South America, Australia and New Zealand. In these areas, homosexual and bisexual men and intravenous drug users are the major affected groups. While heterosexual transmission accounts for a much smaller percentage than among homosexuals, it is increasing. Since blood screening is common, transmission by transfusion is not a continuing problem. Some transmission from infected mothers to their children before or during birth has been documented.

Pattern II areas include parts of Africa and the Caribbean. Sexual transmission of HIV in these areas is primarily heterosexual and is believed to affect up to 25 percent of the 20-40 age group in some urban areas. According to Mann, up to 75 to 90 percent of female prostitutes in Pattern II areas are HIV infected. Transfusion of infected blood and blood products remains a problem, as does the use of non-sterile skin-piercing equipment, but heterosexual transmission plays a much larger role. Perinatal transmission is a substantial problem.

Pattern III areas include Asia, most of the Pacific region and the Middle East and Eastern Europe. Here, although the virus is present, the infection has not yet penetrated into the general population. Most AIDS cases involve homosexual or heterosexual contact or receipt of infected imported blood or blood products.

The WHO global strategy, approved last May by the member countries, has three major goals -- preventing HIV infection; reducing the personal and social impact of infection, including the care of those already afflicted; and unifying national and international efforts.

Mann was asked last week whether he feared that the emphasis on informing all the world's people about AIDS and the threat to humanity that the WHO believes it poses might cause international panic. "If we have to choose between people being a little bit scared or being ignorant," he said, "we would rather they be a little bit scared."