The source of America’s biggest Cyclospora outbreak in years remains a mystery – but experts say there is one alarming way the parasite could, in theory, spread.
The infection has sickened more than 18,000 people across 45 states since May, leaving over 400 hospitalized and investigators searching for answers.
Now, experts speaking to the Daily Mail have revealed the one scenario in which the parasite could spread from person to person – despite decades of evidence suggesting it cannot.
Cyclosporiasis spreads via the fecal-oral route, typically when someone eats food or drinks water that has been contaminated with human feces.
After exiting the body, the parasite takes one to two weeks to mature in the environment before becoming infectious. This, experts say, opens a crucial window that could allow it to spread between people.
In this scenario, someone infected with Cyclospora fails to wash their hands after using the bathroom and touches a surface, such as a bus or subway handrail.
This transfers the parasite’s eggs and, if they remain there long enough to mature into their infectious form, another person could later pick them up on their hands and become infected after touching their mouth.
Known as fomite transmission, this is a well-recognized route by which many infectious diseases spread from person to person.
Could you catch this from a surface? Theoretically, yes — if the parasite survives and ends up in someone’s mouth, according to Dr Kelley Steury, a public health specialist
In the early days of the Covid pandemic, scientists feared the coronavirus was spreading this way, prompting people to disinfect groceries, wipe down deliveries and regularly sanitize high-touch surfaces, such as elevator buttons, door knobs and handles on public transportation.
Later evidence showed airborne transmission was overwhelmingly responsible for most infections.
Dr Kelley Steury, a public health expert, said: ‘Could someone become sick just by touching the same surfaces as a sick person? Theoretically, yes.
‘If [the parasite] remained in an environment where they could survive, and another person later ingested them, transmission is biologically possible.’
Dr Omer Awan, a physician and senior public health contributor for Forbes, added: ‘A lot of things would have to go right for that to occur. Theoretically, that would be possible.’
He added: ‘You never say never in science. Things always evolve and our understanding of diseases and epidemiology evolves and changes over time.
‘But I would say this is not a time to panic. It’s an outbreak, it appears scary, but I think we can all get through this.’
On its website, even the Centers for Disease Control and Prevention admits that, though rare, it is not impossible for the parasite to spread between people.
The agency says: ‘It takes at least one to two weeks in the environment (outside the body) for Cyclospora to become infectious after passing in a bowel movement.
‘Therefore, direct person-to-person transmission is unlikely.’
The fecal-oral route is also how norovirus, which is behind the seasonal stomach bug, spreads.
About 19 to 21 million people are infected with the virus every year.
Cyclospora parasites are able to endure a range of conditions in the environment, meaning they could persist for weeks.
‘They do have kind of a natural protection against the environment, and they can survive for some time in the environment,’ Dr Brian Labus, an infectious disease epidemiologist at the University of Nevada, Las Vegas, told the Daily Mail.
‘But, if we confirm that it can indirectly spread between people, that means we didn’t understand the biology of this organism at all, and we’re completely wrong about hundreds of years of studying these kinds of organisms.’
He added: ‘It has to have this cycle where it takes time outside the human body to essentially mature into a form that can cause further infections.
‘If it didn’t do that, we would see a lot of cases of this every single year — way more than what we’re seeing in this outbreak.’
That durability, combined with the long maturation period, means the parasite can linger in the environment for weeks before it becomes infectious.
