They call it the Cup bug and it is contagious.

Before this long America's Cup summer ended Thursday, three foreign outfits already had announced their intentions to return in three years to pursue the Cup that no foreigner has won.

The leader for the British next time will be Peter deSavary, a balding banker with connections to Arab oil money. DeSavary announced last week that he had $1.5 million pledged to a British challenge and expected to double that woithout problems.

"He must be a great yachtsman," an American commented to a British journalist who has covered yachting for decades.

"No, no, no, no, no," chortled the Briton. "He's a bloody dinghy sailor. He's just been bitten by the Cup bug."

The bug threatens epidemics among people with -- or with access to -- money who visit Newport during years when the America's Cup is up for grabs. There is something overwhelming about the glitter of a Cup summer -- life in the rented mansions; the beautiful, classy women; the handsome athletes who run the boats; the parties; the high society; the culture and the great abounding sense of health, wealth and endless prosperity.

It transfixes such men as deSavary, who quit high school and worked for two years piling up his fortune, Baron Marcel Bich, who rose from the bourgeoisie to captain of a ballpoint pen dynasty and would up spending 10 years and $18 million trying to capture the Cup.

It is not hard for men of wit and industry to raise the money to mount a Cup campaign, and the rewards are instantly tangible even if they never win a race.

But is it worth it?

"I'm not sure that it was," said Jim Hardy, who spent his summer here this year captaining Australia, only to see her go down to defeat, 4-1, in the final Cup series against the U.S. defender, Freedom.

It was the third time Hardy had piloted a yacht into the Cup finals and the third time he had lost. "I'm afraid I'm not a very good loser," said the millionaire winemaker.

But there are plenty waiting to fill his shoes.

The French will be back in 1983, though Baron Bich has finally called it a day. The Swedes are working on a new 12-meter after bitter failure this time. DeSavary is organizing and the Australians will be back with John trand taking over in place of Hardy.

Bich had no regrets when he left Newport for the last time as a challenger a week ago. He had this to say. "I am doing this for 15 years because I love the 12-meters. And I think the New York Yacht Club knows that the love is the most important thing in life."

The U.S. crews and syndicates for Clipper and Freedom will be revived and there is a syndicate aiming to build a new Congrageous and call it Courageous II.

One day after the 1980 Cup is over, it's all alive and building for three years hence.

Interest in the Cup no doubt was helped along this year by some startling innovations that gave aspiring challengers and defenders new avenues to travel. i

At the start of this year's campaign the general view among knowledgeable observers was that there wasn't any significant difference between one boat and the next.

Technology had not changed in six years and design had been much the same for 13 years. In 1967, Intrepid extablished the line on which all 12-meters were drawn, and in 1978, established the new material, aluminum.

"It will be decided this year on small novelties.

Freedom skipper Dennis Conner's approach -- using two boats full-time but campaigning only one of them in actual racing; spending two years and sailing more than 300 days a year to build total competency -- set a new standard.

Said Hardy when it was over, "I'm just a winemaker and a weekend sailor. Our time is finished. Dennis Conner proved that."

The development of a new breed of sails -- those made of the space-age fabric called Mylar-Kevlar -- opened a door to the sailmaking industry. The significance of this stretch-free, ultralight fabric has not even been guessed at yet but John Marshall, president of North Sails, says it will revolutionize the racing industry.

Then the British came along with their bendy-topped mast, fabricated by replacing the top 20 feet of a conventional 12-meter aluminum mast with flexible fiberglass. The effort was a major increase in allowable sail area and undeniable advantage in certain conditions.

The problem was that the British and then the Australians, who built another bendy mast in a great hurry, never had time to design a boat to take full advantage of the new spar. Both boats were faster than anyone else in the light air but out of control when the wind piped up.

That will be rectified on the designers' drawing tables. It will mean, according to all top sailors and designers, a new breed of 12-meters that are slightly longer and slightly heavier thant the current ones.

It also will mean a great deal of new business for yacht designers and yacht builders.

"That does not worry us at all," smiled Bill Langan, chief designer at Sparksman & Stephens, where Freedom was drawn.

All anyone needs to get involved in this mad rush to high times is two or three million dollars or access to people who have that kind of money.

It's all tax deductible, of course, in the name of international sport.

Symptoms of the Cup bug disease: euphoria, followed by weight loss in the wallet. It's the same disease for winners and loser. The winners just get it worse.