Gonorrhea cases are rising at an alarming pace across the western United States, even while declining in the rest of the country, the federal Centers for Disease Control and Prevention reported Thursday.
The number of cases in California and seven other western states increased 42% from 2000 to 2005 while declining 10% nationally, according to the report.
An increase in gonorrhea is typically associated with a rise in other sexually transmitted diseases -- most importantly HIV infection.
"This is one of the most significant increases we've seen in gonorrhea in years," said Dr. Lori Newman, an epidemiologist at the CDC and one of the report's authors. "Unless we take action now, we'll be in trouble in the future."
The outbreak is spreading most intensely in Nevada, where the proportion of new cases per 100,000 people went from 77 in 2000 to 123 in 2005, according to the report.
The most dramatic rise was in Utah, which went from 10 new cases per 100,000 people in 2000 to 30 in 2005.
Overall, the CDC reported about 360,000 new cases nationwide in 2005.
Researchers are uncertain why gonorrhea is increasing in the West at such a dramatic rate but surmised that it was at least partly related to an increase in risky sexual behaviors driven by methamphetamine use, Newman said.
More and better screening has also contributed to the rise, Newman added.
Gonorrhea is a bacterial infection that can lead to severe complications in women, including infertility. The disease can be treated with antibiotics.
From 1975 to 1997, cases nationwide dropped 74%, partly because of more intervention and education about sexually transmitted diseases.
The latest CDC report found that gonorrhea cases dropped 22% in the South, 16% in the Northeast and 5% in the Midwest, although some areas now appear to be seeing a small resurgence.
California's outbreak is the largest in the West, with 34,338 cases reported in 2005.
State health officials became alarmed around 2003 when they noticed a rise in gonorrhea cases in counties that had previously reported few. From 2002 to 2003 in Butte County, for instance, new cases jumped from 26 to 143, said Dr. Gail Bolan, chief of the STD Control Branch of the California Department of Health Services.
An investigation there and in other counties with similar increases revealed a rise among prisoners and methamphetamine users, who often engaged in unprotected sex, Bolan said.
Health officials found that some varieties of the bacteria had developed resistance to fluoroquinolone antibiotics, commonly used to treat gonorrhea.
"It's really going to be a challenge to treat this public health problem," she said. The CDC also reported Thursday that rates of the liver diseases hepatitis A, B and C have dropped to historic lows.
The declines in hepatitis A and B are largely due to the advent of effective vaccines in the 1990s, said Annemarie Wasley, an epidemiologist at the CDC's division of viral hepatitis.
Cases of hepatitis A, a virus spread through contact with feces from infected people, have decreased 88% since 1995, the year before routine vaccination was recommended. Cases of hepatitis B, a virus spread through blood or bodily fluids, have dropped 79% from 1990.
Hepatitis C infections, which are common among intravenous drug users, have dropped by 92% since 1992, according to the CDC. There is no vaccine for the virus, but officials said increased screening and efforts to curtail needle sharing have led to a steady decline.