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Dengue epidemics have been occurring in the Caribbean and Central and South America, including Mexico. In 1995, the proximity of these epidemics increased the possibility of cases occurring in Texas. In response, medical and community educational materials were distributed and active surveillance for dengue cases was initiated. By the end of the year, sera from more than 360 patients were tested for anti-dengue antibody. Twenty-nine cases were detected statewide; seven cases in southern Texas were locally acquired. Dengue (DEN) fever results from infection with one of four closely related dengue virus serotypes (DEN-1, DEN-2, DEN-3, and DEN-4). This mosquito-borne illness was once a significant source of morbidity in Texas. The last major outbreak occurred in 1922 when more than 40,000 cases were reported; three-fourths of these cases occurred in Galveston, Texas. 1 In 1923 and 1924, 999 and 369 cases were reported, respectively. Over the next 26 years, excluding 1941 when there was an outbreak of 526 cases, an average of 78 cases (range ϭ 7-257) were reported each year (Texas Department of Health [TDH], unpublished data). 2 Dengue disappeared from Texas between 1950 and 1980, but during the 1980s, there were two outbreaks. In 1980, 63 cases of dengue were reported in Texas. 3, 4 Twenty-three of the patients had no international travel history. In 1986, 17 cases were reported; eight of them had no international travel history. 5, 6 During both the 1980 and 1986 outbreaks, DEN-1 was the only serotype isolated from patients with locally acquired infections. From 1987 through 1994 a total of seven travel-related cases were reported. 7 The emergence of dengue in the Americas in recent decades is a significant public health problem. 8 Since 1980, both endemic and epidemic virus transmission has occurred throughout the Caribbean and Central and South America. In 1995, there were reports of more than 180,000 cases of dengue in South America, 68,000 in Central America, and 17,000 in Mexico (Pan American Health Organization, Communicable Disease Program, unpublished data). On August 25, 1995, the TDH was notified of an ongoing dengue fever outbreak in Reynosa, Tamaulipas, Mexico, approximately 10 miles south of McAllen, Texas in Hidalgo County. The proximity and timing of the Reynosa outbreak and the fact that the dengue virus vectors Aedes aegypti and Ae. albopictus are commonly found in much of the eastern two-thirds of Texas greatly increased the likelihood of cases in Texas. Educational and surveillance efforts were implemented and evaluated.

False negativity in a commercial anti-HIV kit (IMx HIV-1/HIV-2 3rd Generation Plus (code 8B32) was investigated, and the kit that superseded it (IMx HIV-1/HIV-2 III Plus, code 8C98) was evaluated. In a comparison on 574 freshly collected anti-HIV-1-positive specimens, 97.2% were more reactive in 8C98 than in 8B32; 35.5% were more than twice as reactive and 8.5% were more than four times as reactive. In 8B32, the signal from 55 specimens selected because of weak reactivity was enhanced 1.5 to 8.8 times by preliminary heating at 56 degrees C for 30 min. The reactivity of the 55 heated sera was then similar to that of the same specimens tested without heat treatment in the 8C98 assay. Reactivity in 8B32 was also increased in 66 of 76 (at least twofold in 20) randomly chosen anti-HIV-positive serum specimens by the addition of EDTA (10 mM final concentration). One of these specimens was false negative (signal:cutoff (S:CO) ratio 0.76) in 8B32, though its reactivity was restored by addition of EDTA (S:CO ratio 9.54). These findings indicate that the inhibitory effect that originally led to false negative findings in 8B32 was probably due to complement activity, and that the same activity was present in the freshly collected specimens used here to evaluate the replacement IMx anti-HIV assay (8C98). The specimen panel employed to evaluate 8C98 included 1,892 anti-HIV-positive and 779 anti-HIV-negative specimens. There were no false negative reactions. The lowest S:CO ratio observed was 6.2 and only 17 (0.2%) anti-HIV-positive specimens gave ratios less than 10. Nine unreproducible false positive reactions arose, all possibly attributable to specimen carryover by the IMx instrument. The performance of 8C98 was also compared with that of 10 other current anti-HIV kits using 21 sets of seroconversion specimens (127 specimens in total), and five performance assessment panels (92 specimens in total) comprised mostly of single bleeds from recent seroconverters. IMx 8C98 was the second most sensitive assay. We found no evidence that the 8C98 kit was prone to the effect that had given rise to false negative results in its predecessor (8B32).

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