Michigan Investigates Lettuce as Possible Source of Cyclosporiasis Outbreak

Health Officials Focus on Salad Greens as Thousands of Illnesses Are Reported

Michigan health authorities have identified lettuce and other salad greens as the leading suspected source of a widespread cyclosporiasis outbreak that has sickened thousands of people across the United States. While investigators have not yet determined the exact type of lettuce, the specific grower, or the supplier responsible, early findings indicate that leafy greens have repeatedly appeared during interviews with infected individuals.

The announcement marks an important step in the investigation, although officials emphasize that the evidence is still preliminary. Other foods have not been ruled out, and researchers continue tracing supply chains to determine where the contamination may have occurred.

The outbreak has drawn national attention because of the unusually high number of reported illnesses, particularly in Michigan, which has recorded the overwhelming majority of confirmed cases.

Michigan Records the Highest Number of Cases

According to the Michigan Department of Health and Human Services (MDHHS), the state has reported approximately 2,640 confirmed cases of cyclosporiasis, making it the hardest-hit state in the ongoing outbreak.

Nationwide, nearly 3,000 cases have been identified across 31 states, according to the U.S. Centers for Disease Control and Prevention (CDC). Health experts believe these numbers could continue to rise because there is often a delay between exposure to contaminated food and the onset of symptoms.

Officials say tracking the outbreak has been challenging because many patients cannot remember exactly what they ate several weeks earlier. Additionally, leafy greens often move through complex distribution systems before reaching grocery stores and restaurants, making it difficult to identify a single contamination point.

What Is Cyclosporiasis?

Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis. The parasite infects the digestive system after a person consumes contaminated food or water.

Unlike bacterial food poisoning, Cyclospora infections usually require the parasite to mature in the environment before becoming infectious. This means direct person-to-person transmission is considered extremely rare.

The illness has increasingly been linked to imported fresh produce such as:

Lettuce
Salad mixes
Fresh herbs
Basil
Cilantro
Parsley
Raspberries

Fresh fruits and vegetables are particularly vulnerable because they are often consumed raw without cooking, allowing parasites to survive until they are eaten.

Why Lettuce Is Under Investigation

Michigan's Chief Medical Executive, Dr. Natasha Bagdasarian, stated that interviews with patients repeatedly identified lettuce as a commonly consumed food before illness developed.

She explained that while lettuce appears frequently during investigations, officials cannot yet determine:

Which variety of lettuce may be contaminated.
Which farm produced it.
Which distributor or supplier handled it.
Whether contamination occurred during growing, harvesting, processing, or transportation.

Investigators are comparing grocery receipts, restaurant purchases, supplier records, and laboratory testing to establish stronger evidence before identifying any specific product.

Health officials caution that consumers should not assume all lettuce is contaminated, but they should remain vigilant until the investigation is complete.

Understanding How the Parasite Spreads

The parasite responsible for cyclosporiasis spreads primarily through contaminated food or water.

Contamination can occur when produce comes into contact with:

Contaminated irrigation water
Unsanitary farming conditions
Improper handling during harvesting
Poor washing during processing
Contaminated water used for cleaning vegetables

Because lettuce has many folds and layers, tiny parasite eggs can cling to its surface. Standard rinsing may reduce contamination but cannot always eliminate microscopic parasites completely.

Unlike many bacteria, Cyclospora cannot multiply inside food. Instead, contamination usually happens before produce reaches consumers.

Symptoms Can Appear Days Later

One reason the outbreak has been difficult to investigate is the parasite's relatively long incubation period.

Symptoms generally appear about one week after eating contaminated food, although they can develop anywhere from 2 to 14 days later.

Common symptoms include:

Severe watery diarrhea
Persistent fatigue
Loss of appetite
Stomach cramps
Nausea
Gas and bloating
Weight loss
Body aches
Low-grade fever

Many patients describe the diarrhea as extremely intense and difficult to control.

Some people experience symptoms for several weeks if treatment is delayed.

Why Dehydration Is a Serious Concern

Among the most dangerous complications of cyclosporiasis is dehydration.

Repeated episodes of watery diarrhea can quickly cause the body to lose:

Water
Electrolytes
Essential minerals

Symptoms of dehydration include:

Extreme thirst
Dry mouth
Dizziness
Reduced urination
Weakness
Rapid heartbeat

Young children, older adults, pregnant women, and people with weakened immune systems face the highest risk of severe dehydration.

Hospital treatment may involve intravenous fluids for patients who cannot replace lost fluids by drinking water alone.

Hospitalizations Continue to Rise

According to the CDC, at least 86 people have required hospitalization during the outbreak.

Health experts note that hospitalization numbers may increase because many recent infections have not yet been fully reported.

Unlike many foodborne illnesses, Cyclospora infections often take longer to diagnose because specialized laboratory testing is needed to identify the parasite in stool samples.

Many patients initially believe they have a stomach virus before seeking medical care.

Treatment Is Available

Fortunately, cyclosporiasis is treatable.

Doctors generally prescribe the antibiotic trimethoprim-sulfamethoxazole (TMP-SMX), which effectively eliminates the parasite in most patients.

Treatment also includes:

Drinking plenty of fluids
Replacing electrolytes
Getting adequate rest
Eating easily digestible foods

People who are allergic to sulfa medications should consult their physician regarding alternative treatment options.

Without treatment, symptoms may persist for several weeks or even recur over time.

Why Washing Produce Matters

Michigan health officials are encouraging consumers to take additional precautions while the investigation continues.

Recommended safety measures include:

Buying whole heads of lettuce instead of prepackaged salads
Rinsing lettuce thoroughly under running water
Discarding the outer leaves
Cleaning kitchen surfaces regularly
Separating fresh produce from raw meat
Cooking vegetables whenever practical

Although washing cannot guarantee complete removal of Cyclospora, it may reduce the number of contaminants on the surface.

Officials stress that consumers should never wash produce using soap or household detergents, as these products are not intended for food and may leave harmful residues.

Why Prepackaged Salads Are Being Avoided

Health authorities specifically advised consumers to avoid prepackaged salads until investigators learn more about the outbreak.

Prepackaged salads often contain mixtures of:

Romaine lettuce
Iceberg lettuce
Spinach
Spring mix
Other leafy greens

Because multiple farms and suppliers may contribute ingredients to a single bag of salad, identifying the original contamination source becomes much more difficult.

Whole heads of lettuce generally have shorter supply chains and allow consumers to remove outer leaves before washing.

Challenges Facing Investigators

Foodborne outbreak investigations are complex.

Researchers must:

Interview thousands of patients.
Compare food histories.
Trace produce distribution networks.
Collect laboratory samples.
Test food and environmental sources.
Coordinate with multiple state and federal agencies.

Even when lettuce is identified as a likely source, proving exactly where contamination occurred may take weeks or months.

Sometimes investigations conclude without identifying a single farm or supplier because contaminated products have already been consumed or discarded.

Economic Impact on Farmers and Retailers

Large foodborne outbreaks often affect the agriculture industry as well.

Even growers who are not connected to the outbreak may experience:

Reduced consumer demand
Lower sales
Cancelled restaurant orders
Financial losses

Retailers may voluntarily remove products from store shelves if they suspect possible contamination.

Restaurants may also revise menus or temporarily stop serving certain leafy greens until more information becomes available.

Public Health Response

State and federal health agencies continue working together to:

Identify contaminated food products.
Notify consumers of potential risks.
Conduct laboratory testing.
Trace food distribution networks.
Monitor new illness reports.
Provide treatment recommendations.

Officials are also educating healthcare providers about recognizing cyclosporiasis, since early diagnosis helps patients receive appropriate treatment sooner.

What Consumers Should Do

Health experts recommend that consumers remain cautious but not panic.

People should:

Wash fresh produce carefully.
Throw away damaged or spoiled vegetables.
Choose whole lettuce heads when possible.
Practice good kitchen hygiene.
Stay hydrated if gastrointestinal symptoms develop.
Seek medical attention if diarrhea becomes severe or prolonged.

Anyone experiencing symptoms after eating fresh produce should inform their healthcare provider about what they recently consumed. This information helps investigators identify common exposure patterns.

Looking Ahead

The investigation into the Michigan cyclosporiasis outbreak remains ongoing, and health officials continue analyzing patient interviews and food distribution records. While lettuce has emerged as the strongest suspected source, authorities stress that the evidence is not yet conclusive. Additional food items remain under investigation until laboratory testing and supply-chain analysis provide clearer answers.

In the meantime, public health agencies are urging consumers to take simple precautions, including choosing whole heads of lettuce, washing produce thoroughly, and following safe food-handling practices. Since cyclosporiasis can cause severe diarrhea, dehydration, and prolonged illness, early medical attention and proper treatment are essential for anyone experiencing persistent gastrointestinal symptoms.

The outbreak serves as a reminder of the importance of food safety throughout the supply chain—from farms and processing facilities to grocery stores and home kitchens. As investigators continue their work, consumers are encouraged to stay informed, practice good hygiene, and follow official public health guidance to reduce the risk of infection.

Tag: Lettuce contamination

Michigan health officials say that lettuce and other salad greens may be linked to illnesses that cause diarrhea.