DES MOINES — Mexico’s agriculture department confirmed the influenza strain that has infected almost 4,300 people in 33 countries did not originate from hogs at a Smithfield Foods operation, which critics of modern pork production and others singled out as the source of the A-H1N1 flu virus. But the damage to the pork industry has already been done.

"Before the flu outbreak, pork producers were losing money, but things were looking up because we were heading into the grilling season," said Neil Dierks, chief executive of the National Pork Producers Council. "When this flu was misnamed, things went south, and producers’ losses nearly doubled."

On April 24, the first day the flu outbreak, pork producers were losing $10.91 per pig. After two weeks of the international media erroneously reporting on the "swine" flu, pork prices fell dramatically. Producers lost an average of $20.60 per pig, or nearly $8.4 million, a day.

Pork prices dropped as domestic demand slumped and import bans on U.S. pork were slapped on by U.S. trading partners, including Russia and China. Russia’s ban now applies only to 11 states, most of which are not major pork producers. At least 12 countries that banned, or indicated they would ban, U.S. pork now have reversed their decisions.

From the beginning, experts cautioned against labeling this virus as swine flu. After news of the flu outbreak broke, the U.S. Centers for Disease Control and Prevention stated: "This (flu) virus is different, very different from that found in pigs." On April 26, the World Organization for Animal Health said the H1N1 influenza never should have been named "swine" flu and that there was no justification for the imposition of trade restrictions, a position also taken by the W.T.O.

N.P.P.C. as well as public health and agriculture agencies from around the world repeatedly pointed out that pork is safe to eat and handle and that flu viruses are not transmitted through food.

"Speculation on the A-H1N1 flu’s connections to the Mexican farm specifically, and to hog farms generally, would be irresponsible and would only bring further injury and pain to pork producers for something that was not of their making," Mr. Dierks concluded.