Washington, August 26 : A study has linked typhoid fever cases in the U. S. to international travel, especially to India, Pakistan, and Bangladesh.

The study also shows an increase in certain strains of typhoid fever that are resistant to the most commonly used medications for treatment.

"Infection with Salmonella ser Typhi causes an estimated 20 million cases of typhoid fever and 200,000 deaths annually worldwide," the authors provide as background information.

They say that typhoid fever is a rare disease in America, with approximately 300 clinical cases reported each year, and that improvements in municipal water and sewage treatments in the country resulted in dramatic declines in the incidence of and deaths from typhoid fever at the beginning of the last century.

According to them, the majority of the cases that were seen in the U. S. in the recent past were associated with foreign travel.

"Over the last 20 years, emergence of S Typhi strains resistant to antimicrobial agents has complicated treatment of infected patients," they wrote.

They further report: "Identification of nalidixic acid-resistant S Typhi (NARST) and reports of infection with S Typhi strains resistant to ciprofloxacin from typhoid-endemic areas have generated concern that strains resistant to fluroquinolones may become more prevalent."

Dr. Michael F. Lynch, and colleagues, from the Centers for Disease Control and Prevention (CDC), Atlanta, reviewed data from 1999 to 2006 for 1,902 persons with typhoid fever who had epidemiologic information submitted to the CDC, and
2,016 S Typhi isolates from public health laboratories sent to the CDC for antimicrobial susceptibility testing.

The median (midpoint) age of patients with typhoid fever was 22 years.

The authors report: "1,295 (73 percent) were hospitalised and 3 (0.2 percent) died. Foreign travel within 30 days of illness was reported by 1,439 (79 percent). Only 58 travelers (5 percent) had received typhoid vaccine."

They even said that the three countries in the Indian subcontinent accounted for more than two-thirds of all travel associated cases of typhoid fever-India (47 percent), Pakistan (10 percent) and Bangladesh (10 percent).

The authors write: "Patients with resistant infections were more likely to report travel to the Indian subcontinent: 85 percent of patients infected with MDRST and 94 percent with NARST traveled to the Indian subcontinent, while 44 percent of those with susceptible infections did."

The study has been published in JAMA. (ANI)