EPIDEMIC : Cholera--One Year Later : The epidemic that first hit Peru had affected 12 Latin American countries by late 1991, with 400,000 cases and 4,000 deaths. Now it has crossed into Argentina.

Now in its second year, the South American cholera epidemic has spread recently to Argentina, and many of the continent’s countries are resigning themselves to a long struggle against the potentially fatal disease.

Cholera has long been endemic in parts of Asia and Africa, but it had not struck in South America since early this century. The bacteria thrives in poverty, where poor sanitation helps it spread from the excrement of those who are infected to new victims through contaminated food and water.

It causes severe diarrhea, which quickly dehydrates the body and can lead to death if untreated.

BACKGROUND--In late January of last year, cholera broke out on the northern coast of Peru. Within weeks, an epidemic was sweeping through other parts of the country and north into neighboring Ecuador.

By the end of the year, it had hit a dozen Latin American countries, with nearly 400,000 reported cases and 4,000 deaths. Peru’s toll was by far the largest: 320,000 cases and 2,900 deaths. Ecuador was second with 46,000 cases and nearly 700 deaths, and Colombia was third with 12,000 cases and 200 deaths.

The epidemic ranged as far north as Mexico, where 2,700 cases and 34 deaths were reported. The United States reported 25 cases, mostly brought in by travelers, but no deaths.

After subsiding in the second half of 1991, cholera is on the rise again this year in Peru, where seasonal warmth is aiding its propagation. The resurgence brought reports of 27,000 new cases and 111 deaths between Dec. 29 and Feb. 1.

And for the first time, cholera has moved into the underdeveloped back lands of northern Argentina, coming from neighboring Bolivia. In the past week, the number of cases in Argentina has more than doubled, reaching nearly 200, with 11 reported deaths.

Argentina had hoped that its relatively well developed systems of public health and hygiene would keep it safe.

OUTLOOK--The Argentine government is taking measures to contain the outbreak in the north, but some analysts say it may be only a matter of time before the disease reaches the Buenos Aires metropolitan area, where about a third of Argentina’s 35 million people live.