Delta passenger James Tonges seemed calm enough today telling ABC he was taking an anti-HIV drug after biting into a needle-laden turkey sandwich - but he still has a lot of worry to chew on.

Tonges will "certainly" have sleepless nights over the incident, wondering about his health, according to Dr. William Schaffner, chairman of Preventive Medicine at Vanderbilt University Medical Center in Tennessee. The risk is small, but he could have been exposed to the HIV virus or hepatitis B or C.

Half a dozen sewing needles were found on four separate flights from Amsterdam bound for Minneapolis-St. Paul Airport.

"It's quite understandable to have confusion and anger over what happened with a needle hidden in a sandwich," said Schaffner. "Needles have nothing to do with making sandwiches in my house. Someone must have put them there."

Doctors put Tonges on the antiretroviral drug Truvada, which was just approved by the Food and Drug Administration this week for HIV prevention. The drug has been used in the past for post-exposure to the virus and off-label for health care workers who are inadvertently exposed to the virus through needle accidents.

"It was on the second bite into the sandwich, it actually poked the top of my mouth. It was about one inch long, straight needle. It was on the second bite into the sandwich, it actually poked the top of my mouth," Tonges told "Good Morning America". "Since it punctured the top of my mouth, I had to be put on medication, and we're waiting to see if there's any type of substance on the needle. They're doing their examination right now."

"Right now, they say I am OK," he said. "They said if I started developing symptoms like nausea and headaches, go to the emergency room right away. It's just a wait-and-see game now."

A person cannot acquire HIV through ingestion, but the virus could be transmitted through a puncture wound such as the one Tonges experienced. Short-term use of the drug - usually three months - has few side effects, according to Schaffner.

HIV can survive on a surface like a needle for a period of days, depending on whether it has dried or the nature of the surface and conditions like humidity. The risk is small, but real, and patients need "a lot of education and assurances," he said.

"The deeper the inoculation the more likely the establishment of actual infection," said Schaffner. "Likewise, the more blood-inoculated, the greater the risk. In this case, the 'stick' was very slight, as far as I know, and no blood was visible on the needle. The risk of infection should be low - and made even lower by Truvada."

The sandwiches were provided by the gourmet catering company Gate Gourmet, based at Schipol Airport and go on more than 900 flights every day. Authorities are treating it as a criminal act and say it represents a gaping hole in airline security.

The incident is reminiscent of the 1982 Tylenol tampering scandal, when seven people died after taking the over-the-counter painkiller. Unknown suspects put 65 milligrams of deadly cyanide into the extra-strength capsules, more than 10,000 times the amount necessary to kill a human.

Law enforcement speculated that an "over the counter" terrorist was at large and Americans were gripped with fear. Poison control centers were flooded with calls, according to a Newsweek report at the time.

"A nasty person is probably out there doing something like this," said Schaffner of the Delta incidents. "You always have to worry about needles … especially where we don't know the source."

Schaffner said for the past 20 years, doctors, nurses and others who have been occasionally exposed to needle sticks in health care settings have been given anti-retrovirus drugs retroactively. "Sometimes it's an unknown source and sometimes we know the patient source," he said.

But the patient often thinks, "It's nice to say the risk is low, but it could be 100 percent for me," said Schaffner. "They are worried about their own individual circumstances. Suppose the arrow hits me."

He treated a young female intern who had a needle stick. "Occasionally something unexpected happens," he said. "All of a sudden the patient jerks and you find the needle in you…It's amazing what still happens."

"I reassured her she was sell taken care of - I even spoke to her parents," he said. "But she called me in the middle of the night once and I talked to her for about a half hour."

In another incident, a teaching faculty member was splashed in the eye by blood before eye protections were introduced. During the infection surveillance period, she was advised to not to get pregnant. Six months later, all turned out negative and she was told to embrace life and not worry about developing HIV. But, she decided not to have a baby.

"The point is that these exposures can have a fairly profound effect on people, even if it turns out perfectly fine," said Schaffner. "They are psychologically disturbing."