If you're headed to a freshwater stream this summer and a friend dares you to eat a raw crayfish（小龙虾） – don't do it. You could end up in the hospital with a severe parasitic¹（寄生的） infection. Physicians at Washington University School of Medicine in St. Louis have diagnosed a rare parasitic infection in six people who had consumed raw crayfish from streams and rivers in Missouri. The cases occurred over the past three years, but three have been diagnosed since last September; the latest in April. Before these six, only seven such cases had ever been reported in North America, where the parasite²（寄生虫，食客） , Paragonimus kellicotti, is common in crayfish.

"The infection, called paragonimiasis（肺吸虫病） , is very rare, so it's extremely unusual to see this many cases in one medical center in a relatively³ short period of time," says Washington University infectious diseases specialist Gary Weil, MD, professor of medicine and of molecular⁴ microbiology（微生物学） , who treated some of the patients. "We are almost certain there are other people out there with the infection who haven't been diagnosed. That's why we want to get the word out."

Paragonimiasis causes fever, cough, chest pain, shortness of breath and extreme fatigue⁵（疲劳） . The infection is generally not fatal, and it is easily treated if properly diagnosed. But the illness is so unusual that most doctors are not aware of it. Most of the patients had received multiple treatments for pneumonia⁶（肺炎） and undergone invasive procedures before they were referred to Barnes-Jewish Hospital or St. Louis Children's Hospital at Washington University Medical Center.

The half-inch, oval-shaped parasitic worms at the root of the infection primarily travel from the intestine⁷（肠） to the lungs. They also can migrate to the brain, causing severe headaches or vision problems, or under the skin, appearing as small, moving nodules（小瘤） .

Some of the patients had been in and out of the hospital for months as physicians tried to diagnose their mysterious illness and treat their symptoms, which also included a buildup（组合，增强） of fluid around the lungs and around the heart. One patient even had his gallbladder（胆囊） removed, to no avail（无效） .

"Some of these invasive procedures could have been avoided if the patients had received a prompt diagnosis⁸," says Michael Lane, MD, an infectious diseases fellow at the School of Medicine who treated some of the patients. "We hope more doctors will now have this infection on their radar⁹ screens for patients with an unexplained lingering（拖延的） fever, cough and fatigue."

Once the diagnosis is made, paragonimiasis is easily treated with an oral drug, praziquantel（吡喹酮） , taken three times a day for only two days. Symptoms begin to improve within a few days and are typically gone within seven to 10 days. All the patients have completely recovered, even one patient who temporarily lost his vision when parasites¹⁰ invaded the brain.

The recent infections, which occurred in patients ages 10-32, have prompted the Missouri Department of Health & Senior Services to issue a health advisory¹¹ alerting doctors across the state. The department also printed posters warning people not to eat raw crayfish and placed them in campgrounds and canoe（独木舟） rental¹² businesses near popular Missouri streams. Thoroughly¹³ cooking crayfish kills the parasite and does not pose a health risk.