EARLY LAST MONTH, when a Zairean virologist suspected that patients in the city of Kikwit might have the dreaded Ebola virus, there was only one laboratory in the world he could turn to: the Centers for Disease Control and Prevention in Atlanta.

Only five labs worldwide even come close to meeting the BL-4 (Biohazard Level 4) security standards prescribed for diagnosis and study of super-lethal, incurable viruses such as Ebola.

And only one civilian lab -- the CDC's Special Pathogens Laboratory -- also has the experienced personnel, support staff and safety track record to handle Ebola and similarly dangerous microbes, officials of the World Health Organization said last week.

In a series of far-ranging interviews about lessons learned from the Ebola outbreak, public health experts applauded the swift resolution of the epidemic.

But they warned that personnel and equipment were stretched so thin that if they had been called upon to deal with another epidemic involving an incurable virus like Ebola, the CDC, World Health Organization and allied agencies would have been overwhelmed.

"We dodged a bullet on this," said a highly placed U.S. official who asked not to be identified. "There was a lot of luck involved, starting with: We were lucky the virus broke out someplace so remote and impoverished that it couldn't spread anywhere."

Dr. Ruth Berkelman, of the CDC's Infectious Diseases Division, agreed. "Yes, we did a great job controlling Ebola, once we knew it was there [four months after the epidemic started]. And we're glad that we didn't have two such outbreaks at the same time."

The CDC lab took only two days to identify Ebola in the blood and tissue samples sent in early May by Dr. Tamfun Muyembe of the University of Kinshasa. Partly because of efforts by an international medical team, and partly because of what appears to be a natural decline in virulence, the virus has been on the wane after killing more than 160 people.

At the CDC's BL-4 laboratory in Atlanta, a crew of just six scientists toiled around the clock in rotating shifts throughout the Ebola crisis. Budget cuts and congressionallymandated downsizing have left the lab seven scientists short of its staffing level in the 1980s.

Shortly after the lab confirmed on May 9 that blood samples from Kikwit contained the Ebola hemorrhagic fever virus, the lab's director, Dr. C.J. Peters, wrote memos to his superiors warning that exhaustion caused by overwork among his staff could lead to a serious accident. Because of the specialized nature of BL-4 work, the agency could not fill the gaps by simply drafting personnel from other sections of the CDC.

As a result, the lab has been severely taxed by the thousands of human and animal blood and tissue samples arriving from Zaire as investigators try to determine the full scope of the epidemic and find its animal source.

Like deep-sea divers, BL-4 researchers work encased in cumbersome protective suits, drawing air pumped in from outside. All air, water and refuse from the laboratory undergo several rounds of sterilization before leaving the facility.

Though many -- perhaps most -- of the Zaire samples may prove negative for Ebola infection, all must be handled with the same level of care and caution a scientist might exercise while working with weapons-grade plutonium. Any slipup could be swiftly lethal to the scientists and might endanger society, should the organism escape BL-4 containment.

Twenty years ago, the CDC was able to respond in such crises by shifting some of the laboratory work in two directions: Samples thought to be less dangerous, such as a new strain of influenza, could go to the CDC's next most secure facilities, the BL-3 labs, while some of the most dangerous BL-4 load could be shared by one of the four other maximum security labs in the world.

But sources at WHO said last week most of the other BL-4 options are no longer reasonable. Moscow has a BL-4 lab -- a holdover from the heyday of Soviet big science -- but its security and safety have deteriorated in recent years, along with other aspects of Russian public health and research. Britain's Porton Down biological warfare facility in Salisbury no longer meets BL-4 standards because of budget cuts.

For decades the leading backup to the CDC was the Institut Pasteur in Paris. But WHO officials are now reluctant to direct its "hot" samples to the French lab because a scientist there became sick with Ebola last fall after studying Ebola-contaminated blood. The blood sample came from Cote d'Ivoire, where a Swiss researcher performing autopsies on chimpanzees had been infected with a previously unknown strain of the virus. Both researchers survived.

That leaves only one alternative: the U.S. Army's Ft. Detrick laboratory in Maryland. There, too, downsizing and budget cuts have taken a toll, as the Defense Department seeks to reduce its share of the national debt. Though C.J. Peters formerly worked at the Ft. Detrick lab and maintains close contact with colleagus there, he was unable to persuade the Army facility to help analyze samples from Zaire, CDC sources said. Sources at Ft. Detrick could not be reached for comment.

The Army, however, will soon provide seven experienced BL-4 scientists on temporary loan to the CDC to supplement the exhausted Special Pathogens staff. SIDEBAR

MEANWHILE, the CDC has been reluctant to pass non-Ebola work down the security tier to its two BL-3 facilities. Those 40-year-old lab buildings have so deteriorated that inspectors from outside the government urged that they be condemned more than five years ago.

Most alarming was the discovery that several of the ventilation systems designed to pull potentially contaminated air away from scientists and up through biohazard filters were actually blowing in the opposite direction. And three scientists in the last five years have become ill with the organisms they were studying. Although none died, the infections clearly indicate the dangers in these facilities, Berkelman said.

After the outside report, the U.S. Public Health Service requested funds from Congress for construction of a new BL-3 laboratory.

Since then Congress has appropriated $88 million for the lab. Of that, $1 million was spent on feasibility and design studies. The rest has been accumulating in an earmarked account, awaiting more money to purchase land and construct the lab. At least another $20 million is needed.

A few weeks ago, as part of its overall budget rescissions, the House voted to rescind $40 million of that accumulated fund, and apply it toward the national debt. The Senate voted to rescind all $87 million in the fund. President Bill Clinton has threatened to veto the budget rescission package.

Clinton hopes to salvage at least $47 million of the BL-3 funds, said Victor Zonana, spokesman for Health and Human Services Secretary Donna Shalala.

"This is not the time to be skimping on emerging infectious disease," Zonana said. "The CDC will neither be able to sustain our efforts in emerging diseases nor maintain the safety of our personnel without a new laboratory. The administration believes that the facility is absolutely critical to efforts to keep emerging infections under control, and we will fight to get it built."

Republican staffers for the Capitol Hill committees that oversee HHS and CDC budgets declined to discuss specific decisions concerning the CDC. They emphasized that the funding situation for all aspects of public health is "very fluid," both in terms of taking back money already appropriated and setting future spending. As one staffer put it: "It's all a moving target -- difficult to predict."

Foreign aid funds will be applied to some of the immediate costs of Ebola control, though they cannot be used to improve the CDC's ability to respond to new disease problems. The U.S. Agency for International Development -- itself a target for severe cuts, perhaps even dissolution -- agreed late last week to provide the CDC with $750,000 to offset the costs of its work on Ebola.

In a strange twist, the World Health Organization -- long reliant on U.S. largesse -- is now being seen as a source of funds. WHO initially faced the Ebola crisis with less than $10,000 in discretionary funds. But on May 19, European governments and foundations came up with $2 million in special aid for Ebola control. Now the CDC is praying that the United Nations agency will send it some of that money. A WHO official said such a decision would be sensitive since Zaire, one of the five poorest nations in the world, is arguing it should get the lion's share.

For Americans, an outbreak of an exotic disease in a far-off African country might seem none of their business -- particularly when political attention at home is focused on balancing the budget.

But to public health experts around the world, like Dr. James Le Duc, head of WHO's special virus division, the CDC is the world's No. 1 public health resource.

"The CDC," said Le Duc, "is the only ballgame in town."