Typhoid fever in travelers: who should be targeted for prevention?

To clarify indications for typhoid vaccination, we reviewed laboratory-confirmed cases of typhoid fever reported to the United States Centers for Disease Control and Prevention between 1994 and 1999. To estimate the risk of adverse events associated with typhoid vaccination, we reviewed reports to the Vaccine Adverse Event Reporting System for the same period. Acute Salmonella enterica serotype Typhi infection was reported for 1393 patients. Of these patients, recent travel was reported by 1027 (74%), only 36 (4%) of whom reported having received a vaccination. Six countries accounted for 76% of travel-associated cases (India [30%], Pakistan [13%], Mexico [12%], Bangladesh [8%], The Philippines [8%], and Haiti [5%]). For 626 travelers who traveled to a single country, the length of stay was

Cholera in the United States, 1995-2000: trends at the end of the twentieth century.

To evaluate recent trends in cholera in the United States, surveillance data from all cases of laboratory-confirmed toxigenic Vibrio cholerae O1 and O139 infection reported to the Centers for Disease Control and Prevention between 1995 and 2000 were reviewed. Sixty-one cases of cholera, all caused by V. cholerae O1, were reported. There was 1 death, and 35 (57%) of the patients were hospitalized. Thirty-seven (61%) infections were acquired outside the United States; 14 (23%) were acquired through undercooked seafood consumed in the United States, 2 (3%) were acquired through sliced cantaloupe contaminated by an asymptomatically infected food handler, and no source was identified for 8 (13%) infections. The proportion of travel-associated infections resistant to trimethoprim-sulfamethoxazole, sulfisoxazole, streptomycin, and furazolidone increased from 7 (8%) of 88 in 1990-1994 to 11 (31%) of 35 in 1995-2000. Foreign travel and undercooked seafood continue to account for most US cholera cases. Antimicrobial resistance has increased among V. cholerae O1 strains isolated from ill travelers.

Contrast sensitivity under photopic conditions in the Prospective Evaluation of Radial Keratotomy (PERK) Study.

We studied the effect of radial keratotomy on contrast sensitivity in 69 individuals with one eye operated and one eye unoperated in the Prospective Evaluation of Radial Keratotomy (PERK) Study, with a mean follow-up time of 13.8 months (range 6 months to 31 months). We tested contrast sensitivity under normal daylight conditions using both photographic plates and a computer-video apparatus. On average, we found no clinically meaningful loss of contrast sensitivity in eyes after radial keratotomy. However, eyes with radial keratotomy showed a statistically significant decrease in contrast sensitivity at the higher spatial frequencies of 12 and 18 cycles per degree, although all values were within the previously established normal range. Specifically, 44% of the patients had approximately the same contrast sensitivity in both eyes; 40% of the patients had 50% less contrast sensitivity in the operated eye than in the unoperated eye; 16% of the patients had 50% more contrast sensitivity in the operated eye than in the unoperated eye. Contrast sensitivity improved gradually in operated eyes between 6 months and 2 years after surgery. Eyes with radial keratotomy, in which the diameter of the pupil was the same size as or larger than the central clear zone, had slightly decreased contrast sensitivity compared to eyes in which the pupil was smaller than the clear zone.

Slit-lamp microscopic appearance of corneal wound healing after radial keratotomy.

Radial keratotomy offers a unique opportunity to study corneal wound healing because the corneas are normal, the fine knife blades disrupt adjacent tissue minimally, no sutures are used, there is minimal inflammation, and few postoperative drugs are administered. We studied corneal wounds with a slit-lamp microscope as they healed from two weeks to three years after radial keratotomy in 84 eyes of 51 consecutive patients enrolled in the Prospective Evaluation of Radial Keratotomy (PERK) Study. One day after surgery, the incisions were surrounded by edema. At two weeks, a dense, gray, diffusely marginated opacity occupied 0.1 mm on both sides of the incision. At three months, the area adjacent to the incision was filled with discrete, fine, gray spicules that protruded at right angles from the incision. At six months, the gray cloudiness had completely disappeared, and the individual spicules were more prominent. By one year, the spicules were disappearing from the anterior portion of the incision and were concentrated primarily in the posterior part of the incisions. At two and three years, the incision scar was fainter and the spicules had disappeared from all but the deep posterior part of the wound. We believe that these spicules correspond to the reorganization of the stroma along the edges of the corneal incision. The persistence of the spicules suggests that wound healing in radial keratotomy may not be complete until two years or more after surgery.

Stellate iron lines in the corneal epithelium after radial keratotomy.

Biomicroscopic examinations of the corneal epithelium of 54 patients who had consecutive radial keratotomy operations in the National Eye Institute Prospective Evaluation of Radial Keratotomy (PERK) study showed that abnormal stellate epithelial iron lines had appeared at the junction of the middle and inferior thirds of the cornea in 13 of 16 eyes (81%) examined six months after surgery, in 43 of 50 eyes (86%) examined 12 months after surgery, and in seven of nine eyes (78%) examined 24 months after surgery. The density and pattern of the deposits varied from a faint tan horizontal iron line studded with small branches to a dense yellow-brown deposit with eight radiating arms that extended between all of the incisions. Analysis of the configuration of the iron line and the central keratometric readings 12 months after surgery showed that the greater the reduction in the central keratometric measurement postoperatively, the more prominent the iron line. We attribute the occurrence and variation of the stellate epithelial iron line to irregularities in the surface of the cornea present in the first year after radial keratotomy.

Studies of congenic MRL-Ipr/Ipr.xid mice.

Highly inbred MRL-Ipr/Ipr.xid congenic mice were bred and compared with their + littermates. The xid-bearing congenics developed lymphadenopathy consisting of dull Ly-1+ T cells and impairment of cellular proliferation and IL 2 production in response to the T cell mitogen Con A. Thus, the lpr gene was fully expressed. The xid gene, however, was also expressed as indicated by the failure to respond to immunization with TNP-Ficoll and flow cytometric analysis of splenic B cells. The xid gene was associated with a marked reduction in IgM anti-ssDNA and anti-nDNA of both classes, and serum Ig-bound gp 70. Kidney disease was markedly retarded as was death from the autoimmune process. These studies suggest that the T cell lymphoproliferation and dysfunction characteristic of MRL-Ipr/Ipr mice is not sufficient to induce accelerated autoimmunity; xid is able to markedly slow the process. The xid gene interferes with the development of a B cell subset necessary for maximum autoantibody production, anti-gp 70 production, and the resultant immune complex renal and cardiac disease. The present finding of protection against accelerated autoimmunity in MRL-Ipr/Ipr mice by xid, coupled with previous demonstrations of protection against autoimmunity in other autoimmune mouse strains, suggests that a common approach to the therapy of systemic lupus may be possible.

Comparison of two methods of marking the visual axis on the cornea during radial keratotomy.

We compared two methods of marking the visual axis on the cornea during radial keratotomy surgery in 34 eyes of patients participating in the National Eye Institute Prospective Evaluation of Radial Keratotomy. The locations of the corneal light reflections produced by an optical centering device and by the operating microscope filament were identical in 18 eyes, overlapped partially or touched in ten eyes, and were separate in the remaining six eyes. The two corneal marks in this last group were close enough to make little practical difference. The two methods can be used interchangeably in clinical practice.