FEARING that someone infected in Zaire's Ebola outbreak might land in New York, city health commissioner Dr. Margaret Hamburg declared last month that a surveillance system was in place to identify and quarantine possible cases.

Doctors and hospitals were notified that if a suspected case appeared at their facilities or at JFK International Airport, the person would be sent to a designated isolation ward in one of two selected city hospitals, which she declined to name publicly.

No suspect cases were found. But three potentially serious flaws in the plan became apparent, Hamburg said last week. First, some of the hospital workers unions threatened to strike if their members were ordered to deal with Ebola cases, Hamburg said. Representatives of three unions contacted denied they had made such threats but conceded that "other unions" might have issued such warnings.

Similar threats were made in other U.S. cities, according to Dr. Ruth Berkelman, of the U.S. Centers for Disease Control and Prevention in Atlanta.

The second issue was how to safely do laboratory tests on suspect cases.

"If a suspect case came into a New York hospital, we would obviously want to do routine tests to rule out other causes -- malaria, other viruses -- for the symptoms," Hamburg said, "but there was genuine concern that the hospital labs couldn't handle samples that might contain Ebola."

In the end, the city's public health lab was designated as the testing site. It has a BL-3 (Biohazard Level 3) lab, which is considered adequate for all but the most lethal microbes, such as Ebola. That represented a compromise between some hospital officials who felt that all suspect samples should go to the CDC and those who thought facilities such as Rockefeller University in Manhattan could handle them.

Finally, Hamburg and her counterparts in Chicago, Los Angeles and other major U.S. cities were assured that the U.S. Public Health Service had provided for screening of airline passengers from Zaire. That screening -- in which airline employees were to inspect passengers during the flights, and the U.S. Immigration and Naturalization Service was to give travelers "health alert" information about Ebola symptoms as they passed through U.S. customs -- was the linchpin of all surveillance efforts.

Yet after having flown from Zaire via Lisbon, this reporter passed freely through U.S. immigration and customs at JFK on May 27 without being examined, questioned or given a "health alert" card.

"That is very worrisome," Hamburg said.

Victor Zonana, spokesman for Health and Human Services Secretary Donna Shalala, and CDC representatives were similarly concerned.

"We can't emphasize enough how much we, at CDC, depend upon people at the INS and U.S. Customs, and the airlines, to screen people and distribute this information," CDC spokesman Tom Skinner said.

But a spokesman for the INS insisted that all notifications and examinations had proceeded according to CDC expectations.