Cyclosporiasis outbreak in the United States: Should Australians be concerned?

Thousands of cases of cyclosporiasis have been reported across the United States in what health authorities describe as a significant food borne outbreak. With hundreds of flights operating between North America and Australia each week, some Australians may be wondering whether the parasite could make its way here.

The short answer is that Australians should be aware—but not alarmed.

The outbreak appears to be linked to contaminated food rather than person-to-person spread, making it a very different public health challenge from viruses such as COVID-19 or influenza.

What is cyclosporiasis?

Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis.

The parasite infects the digestive tract after a person consumes contaminated food or water. Fresh produce is the most common source because it is often eaten raw.

Unlike many bacterial food poisoning illnesses, symptoms may not begin until about a week after exposure and sometimes up to two weeks later, making it difficult for investigators to identify the original source.

What does it do?

Most people develop gastrointestinal symptoms including:

• Frequent watery diarrhoea.
• Stomach cramps.
• Bloating.
• Nausea.
• Fatigue.
• Loss of appetite.
• Weight loss if illness is prolonged.

Without treatment, symptoms may last for several weeks and can come and go. Severe dehydration is the main complication, particularly in older people, young children and those with weakened immune systems. Fortunately, effective antibiotic treatment is available for most patients.

Why is there an outbreak?

At the time of writing, investigators have not identified a single food item responsible for this year's outbreak.

Historically, outbreaks have often been linked to imported fresh produce such as:

• Leafy salad vegetables.
• Fresh herbs including basil and coriander.
• Raspberries and other berries.
• Snow peas and similar vegetables.

Because the parasite requires time to mature in the environment before becoming infectious, direct spread from one sick person to another is considered very unlikely. Instead, contamination generally occurs somewhere along the food production or processing chain before the product reaches consumers.

Can infected travellers bring it to Australia?

People can certainly travel while infected because symptoms often do not begin for several days.

However, this is not considered a disease that spreads readily between airline passengers.

Unlike influenza, measles or COVID-19, simply sitting next to an infected traveller is not regarded as a significant transmission risk.

The greater concern is imported contaminated food rather than infected tourists or business travellers.

Can Australia monitor the risk?

Yes.

Australia has an established food safety and public health surveillance system. Doctors and laboratories notify health authorities of confirmed cases, allowing investigators to detect unusual clusters.

Imported food can also be inspected, tested and, where necessary, recalled if contamination is identified.

Health authorities routinely monitor overseas outbreaks because international travel and global food supply chains mean diseases can cross borders even when people themselves do not spread them directly.

Should Australians be worried?

There is no evidence at present that Australia is experiencing a similar widespread outbreak.

Most Australians will never encounter Cyclospora.

The current outbreak in the United States appears to be associated with contaminated produce within particular supply chains rather than an infectious disease spreading rapidly through the community.

For most Australians, sensible food hygiene remains the best protection.

Practical precautions

Health authorities recommend:

• Wash fresh fruit and vegetables thoroughly under running water.
• Refrigerate perishable foods promptly.
• Wash hands before preparing meals.
• Use separate cutting boards for raw foods where appropriate.
• Seek medical advice if severe diarrhoea persists after overseas travel or after eating suspect food.

People returning from overseas who develop prolonged watery diarrhoea should tell their doctor about their recent travel, as specialised stool testing may be required to identify the parasite.

The Times View

International travel means Australians are never completely insulated from overseas disease outbreaks. Fortunately, not every outbreak carries the same level of risk.

Cyclosporiasis is unpleasant and can be debilitating, but it is not spreading through the air, nor is it easily transmitted between people. Australia's best defence is the same one that protects us against many foodborne illnesses: strong surveillance, rapid public health investigation and sensible food safety practices.

The United States outbreak deserves close monitoring, but at this stage it is a reason for vigilance rather than alarm.