Kinshasa, Zaire -- With authorities searching for at least two individuals suspected of having the disease here in the capital, Zaire's chief health official warned yesterday that the quarantine of disease-stricken areas was being violated, and "if the quarantine cannot be held, the country will be closed.

The death toll in Zaire's Ebola outbreak has risen to 77, the World Health Organization reported, out of 84 confirmed cases of the virus.

In Kikwit, the center of the outbreak, authorities acknowledged that more than 100 additional deaths had probably occurred, but had gone uncounted, because the victims died at home. "People do not want to go to hospitals, knowing that the epidemic started there," a WHO statement said.

"Here in Kikwit, the problem is bigger than in Yambuku," where the Ebola virus first broke out in 1976, Zairean microbiologist Jean-Jacques Muyembe told reporters Sunday. "Because the town has more than 400,000 people. It is a very big city. Yambuku was just a village."

In Kinshasa, Ministry of Health officials confirmed that two individuals -- a nurse and a Congo River boat worker -- were being sought by police. The nurse, who was exposed to Ebola in Kikwit, reportedly fled to the capital and disappeared. Reports on her status varied wildly -- from rumors that she had gotten ill but recovered, to claims that she had died on the street in Kinshasa. The riverboat worker, said to have shown symptoms of the disease, was being sought last night on transports along the Congo, a major transportation link between Kinshasa and the interior of Zaire.

Loyangela Bompenda, Zaire's secretary general of health, said yesterday that people are evading roadblocks and violating the quarantine imposed on Kikwit and neighboring villages. "If the quarantine cannot be held, the country will be closed," Bompenda said at a briefing.

Air France, Sabena and other international air carriers have already announced plans to limit flights to the Central African nation.

Bompenda pleaded with citizens and the press corps to abide by the quarantines. And he warned that "control of the Cordon Sanitaire [the quarantine line] is the responsibility of the police. If measures are to be taken, they will be police measures."

Precisely what steps the feared Zairian police might take to enforce the quarantine were not said.

The epidemic has struck Zaire at a time when the country is in near chaos. Throngs of unemployed workers stand idle on the streets of the capital, begging and often trying to steal. Inflation is wildly out of control: The Zaire, the unit of currency, is valued at 5,020 per dollar compared with 90 per dollar just four years ago.

Meanwhile, work continued for the small team of international experts who have gathered to understand and control the outbreak.

Among those now on the ground only two -- Muyembe and South Africa's Dr. Margarethe Isaacson -- have ever seen an Ebola epidemic before.

There is no cure or vaccine for Ebola, which kills up to 90 percent of those it infects. No one knows where the virus hides between epidemics -- in some animal or insect population, for instance. There have been three previous outbreaks, in Zaire in 1976 and in Sudan in 1976 and 1979.

So far, scientists have no idea how and why the virus struck in Kikwit. Muyembe said that a 36-year-old hospital laboratory technician named Kimfumu was the first one struck down in Kikwit's hospital earlier this month. Thirteen hospital staff members who had contact with Kimfumu got the disease, and the epidemic broke out.

But Kimfumu clearly was not the first person to get Ebola in Kikwit. Muyembe said that the unfortunate lab technician had not traveled or participated in any unusual activities. Rather, someone else must have brought the deadly microbe into the hospital.

Though scientists don't yet know who that person was, immediately before taking ill the lab technician had drawn blood samples from dozens of patients suffering from Shigella.

Shigella is an extremely potent bacteria that causes bloody diarrhea. Physicians in Kikwit noted in January that the region was in the grips of a terrible Shigella epidemic. And experts were called in from Kinshasa when the doctors noticed that some of the Shigella patients did not respond to antiobiotic treatment.

Shigella infections usually are easily cured with antibiotics. Those who didn't respond to the drugs, as it turned out, had Ebola.