HD cases were reported from 30 U.S. states (including Puerto Rico) in 2006 (Table 1). A 10 year summary of reported cases is shown in Table 1b, and a graphical representation with comparison to the 10 year trend is shown in Figures 4 and 5 respectively. California, Florida, Louisiana, Massachusetts, New York and Texas contributed the largest number of cases in 2006, and collectively accounted for 63 percent (86/137) of the cases registered. The predominance of these States is in keeping with the ten year trend in reporting, which also would identify New Jersey, Hawaii, Pennsylvania, Washington and Arkansas as the most likely U.S. locations to report HD.

Autochthonous foci of HD transmission are recognized in Hawaii, Puerto Rico and on the U.S. mainland in the region of the western Gulf of Mexico. Some speculate that it also may occur in California. In 2006, a total of nine cases were reported from Hawaii, but only one from Puerto Rico. Reporting from Hawaii generally exceeds the historical trend for the state and was almost exclusively among immigrants from Micronesia or the Trust Territories where HD is highly endemic.

A total of 20 cases were reported from Texas (11) and Louisiana (9). The combined number of cases is consistent with the historical norms from these States, but slightly higher in Louisiana. More than half (13/20) of all these cases were native born U.S. citizens with no residence history outside the United States. Inspection of the Louisiana data also suggests that there is some late reporting of cases that had been diagnosed in earlier years. This may reflect an increasing awareness of disease in the State or an increasing rate of new infection. The consistency of this trend and the potential long term impact of disruptions caused by recent hurricanes on disease awareness and reporting merits additional consideration.