Most U.S. Typhoid Fever Linked to Foreign Travel
A Total Of 47% Of Travel-Related Cases Were In People Who Had Visited India And 10% In People Who Had Visited Pakistan
By Mary Ann Moon
Elsevier Global Medical News
Eighty-five percent of typhoid fever cases in the United States are related
to foreign travel, particularly travel in the Indian subcontinent, investigators
reported in JAMA.
The proportion of typhoid cases associated with foreign travel has always
been high, but it has increased steadily to a new peak during the past few
decades, said Dr. Michael F. Lynch and his associates at the Centers for Disease
Control and Prevention, Atlanta.
The researchers examined trends in typhoid infections in the United States
for 1999-2006 by combining epidemiologic data reported to the CDC's National
Typhoid Fever Surveillance System with data on Salmonella ser Typhi
isolates sent to the National Antimicrobial Resistance Monitoring System for
Typhoid fever continues to be an infrequent infection in the United States,
but it carries substantial morbidity. Nearly three-quarters of cases reported in
the study required hospitalization, which lasted more than 1 week in half of the
cases. Three patients--two who acquired the infection in India and one who
emigrated from Mexico--died of typhoid.
Analysis revealed that the fraction of travel-associated cases in the United
States rose from 64% in 1999 to 85% in 2006. Nearly half of the
travel-associated cases (47%) were in people who had recently visited India,
another 10% in individuals who visited Pakistan, and another 10% in people who
visited Bangladesh. The Philippines, Indonesia, and Cambodia accounted for a
total of 7% of cases.
In the past, Mexico was the chief source of foreign typhoid infections in the
United States. However, Mexico, Guatemala, El Salvador, and Haiti together
accounted for only 13% of cases, while 4% of travelers with typhoid fever had
Only 5% of the 1,094 travelers in the study who reported vaccination status
had received any typhoid vaccine within 5 years of their trip. Typhoid vaccines
are readily available and well tolerated, the researchers noted, and should be
recommended even for travelers whose trips to endemic areas will be shorter than
"Because neither commercially available vaccine is 100% effective, food and
water precautions remain important. Further advice on food and water safety
while traveling can be found at www.cdc.gov/ncidod/dpd/travel.htm ," Dr. Lynch and his colleagues wrote (JAMA
More than half the cases in the study were reported from three states:
California (29%), New York (15%), and New Jersey (7%). Patients' median age was
22 years (range less than 1 year to 90 years).
Of the 391 cases of typhoid fever acquired within the United States, 17% were
traced to a typhoid carrier and 22% were part of typhoid outbreaks.
Typhoid strains that were resistant to antimicrobials were common, with
multi- drug-resistant strains causing 13% of infections. "Notably, about
one-third of all S. Typhi isolates . . . were resistant to the quinolone
nalidixic acid, and the proportion of [strains resistant to this drug] among
U.S. patients steadily increased during the study period," the researchers said.
Resistance to nalidixic acid is a marker for decreased susceptibility to
fluoroquinolones in general. Moreover, most isolates in the study that were
resistant to that agent also showed decreased susceptibility to ciprofloxacin.
"Resistance to ampicillin and to trimethoprim-sulfamethoxazole remains
prevalent and precludes the use of these agents as initial therapy," the
investigators wrote. "A fluoroquinolone remains an appropriate choice for
empirical therapy in adults," they added. "Among children, in whom
fluoroquinolones are limited to off-label use, third-generation cephalosporins
No financial disclosures were reported for the study.