DENVER (AP) _ Fifty people were infected with salmonella after visiting a Komodo dragon exhibit at the Denver Zoo, and the cases were so severe at least one person is still sick three weeks later, a federal report shows.

The Centers for Disease Control and Prevention helped investigate the outbreak in January that resulted in the infections.

State epidemiologist Richard Hoffman said Thursday the CDC found that people who visited a special hands-on exhibit featuring the lizards but failed to wash their hands before eating their next meal or before leaving the zoo also were more likely to contract salmonella.

And officials concluded it was people who touched the wooden enclosure the Komodos were kept in _ rather than those who actually touched the dragons _ who became infected.

Salmonella infection is caused by bacteria spread through contact with several species of infected animals, foods from them, or their feces. Family members also can spread it.

One of the zoo's four dragons has tested positive for a type of salmonella that is common but unusual in appearance. Hoffman said the salmonella's odd appearance helped link the 50 cases to the zoo's lizard.

All of the victims, ages 3 months to 23 years, visited the zoo on Jan. 11 or Jan. 13-16 during its ``Dragon Days'' exhibit, when the lizards were taken out of their usual glass enclosure. However, 13 of the victims lived in a house with another infected person, so Hoffman said it's not known if they were infected directly or by a family member.

Victims were sick for as few as four days and as long as ``26 days and counting,'' Hoffman said, noting that one person hasn't fully recovered. Eight of those stricken were hospitalized.

Hoffman said the lizards apparently defecated in mulch in the enclosure, then walked around and spread the bacteria to the wooden barriers.