More than 120 Massachusetts residents, many from Greater Boston, have contracted a foodborne illness since May 1 that can trigger severe gastrointestinal problems, the state Department of Public Health said Tuesday.
The outbreak of cyclosporiasis — caused by a parasite that is commonly found in the tropics — far outpaces the past three years, in which the state saw only between 18 and 33 reported cases. Just a “small number” of cases in Massachusetts have been connected to international travel, the department said.
“We know this is the tip of the iceberg, and there are plenty of more cases we’re probably not aware of,” said Dr. Larry Madoff, the medical director of the department’s Bureau of Infectious Disease and Laboratory Sciences, in a phone interview Tuesday. “This isn’t a life-threatening infection . . . I don’t think we’re alarmed, but it is something to notice.”
In New York City, public health officials are also warning of an outbreak that has resulted in more than 90 cases between Jan. 1 and July 15. Last year, the city had 56 cases within the same time span, according to a health alert.
Between May and August 2018, nearly 2,300 domestically acquired cases were reported across 33 states, according to the US Centers for Disease Control and Prevention. In late 2017, the CDC reported “baseline levels” of 1,065 cases from 40 states.
The DPH, local health boards, the CDC, and the US Food and Drug Administration are attempting to identify the type of food that spurred the outbreak.
In 2000 and 2004, the illness was linked nationally to raspberries and snow peas from Guatemala. In 2013, the source was bagged salad mix from Mexico. The disease is often seasonal through late spring and summer, with bouts peaking in June and July, Madoff said.
To limit exposure to the infection, especially when eating imported leafy greens and other fresh produce, the Department of Public Health encourages people to practice basic food safety guidelines. That includes washing fruits, vegetables, and kitchen equipment during various phases of food preparation, as well as avoiding cross-contamination. Brushes should be used to scrub fruits and vegetables with thick rinds.
“We should be wary of [cyclosporiasis] till it starts getting better,” said Dr. Jason Harris, a pediatric infectious disease specialist at Mass-achusetts General Hospital. “Without having an idea of what’s causing it, I wouldn’t just count on the cases to fall on their own.”
It can take about a week for someone who’s consumed the parasite to begin experiencing symptoms that include watery diarrhea, appetite loss, abdominal cramping, nausea, and fatigue, according to the DPH. A mild infection usually subsides naturally within a few days, though antibiotics can be prescribed for treatment in some instances.
Young children, in addition to patients who are elderly or who have compromised immune systems, could have complications that last up to several weeks.
“The symptoms and signs overlap with other germs that cause diarrhea,” Madoff said. “I would advise patients if something is persistent — if it’s associated with other symptoms and doesn’t go away — that’s the time to seek medical attention.”
The parasite itself, cyclospora cayetanensis, isn’t transmitted from person to person, unlike other foodborne illnesses that arise from poor hand washing, Harris said. But diagnosis is trickier, Harris said, since bacterial cultures — for instance, to detect E. coli or salmonella — won’t indicate the parasite’s presence.
Instead, a separate lab test will need to be ordered for stool specimens, he said.
“In many ways, this is not atypical for a modern foodborne outbreak where so much of the food production and distribution has become globalized,” Harris said. “That just makes it much harder to trace the root cause of many of these complicated outbreaks.”Alison Kuznitz can be reached at firstname.lastname@example.org. Follow her on Twitter at @AlisonKuznitz.