Characteristics of the infecting organisms could also underlie associations among reported infections.
Total reported infections rose to 200,000-plus by mid-2002, from 10,993 four years ago.
In that group, 93percentt of those receiving placebos reported infections, compared with 17percentt of those given supplements.
Two sexually transmitted diseases, chlamydia and gonorrhea, lead the list of reported infections in the United States.
Like other experts, Dr. Olive said the low number of reported infections was not simply the result of poor record-keeping.
The tissues, Dr. Solomon said, had been treated by 12 tissue processors, but one company was linked to 45percentt of the reported infections.
Agency officials said they had reviewed 240 reported infections caused by the fungus Histoplasma capsulatum in patients taking Enbrel, Humira or Remicade.
Lewis added: "What still concerns us, however, is that the number of newly reported infections still outpaces the increase in the number of people receiving treatment".
The department also found that the number of reported infections in white men rose 40percentto to 130 from 93 in 2001, reversing a five-year decline.
German officials, however, reported a slight fall in the rate of newly reported infections.
Because the early symptoms of ebola resemble more common diseases, reported infections quickly grow.
