Virus Outbreak In Cheese: What You Need To Know

Cheese is a beloved food product, but it can also be a source of foodborne illnesses. Outbreaks of foodborne illnesses attributed to cheese have been reported in the United States, with pathogens such as Salmonella, Listeria, and E. coli being commonly identified. In recent years, there have been several notable incidents involving cheese contaminated with viruses or bacteria. For example, in 2024, an E. coli outbreak affected people in four states and was linked to raw cheddar cheese. In another incident, a Listeria outbreak was linked to cheese produced by a specific company, resulting in illnesses and recalls from major retailers. Additionally, concerns have been raised about the potential presence of bird flu in aged cheese made from raw milk, prompting investigations and testing by the FDA and other authorities. These incidents highlight the importance of proper sanitation, microbiological monitoring, and adherence to food safety regulations in the cheese-making process to protect public health.

Listeria outbreak linked to cheese

Listeria outbreaks have been linked to cheese on several occasions. In one instance, an outbreak was linked to queso fresco and cotija cheese produced by Rizo-López Foods. The outbreak resulted in 26 people infected across 11 states, with 23 hospitalized and 2 deaths.

Another outbreak, which was investigated by the CDC, was linked to deli meat and cheese. The specific product causing the outbreak was not identified, and no recall was issued. However, it was suspected that a contaminated food product introduced the Listeria outbreak strain into delis in multiple states.

In another incident, the FDA, along with the CDC, investigated a multistate outbreak of Listeria infections linked to Brie and Camembert soft cheese products manufactured by Old Europe Cheese, Inc. The outbreak resulted in 6 illnesses in 6 states, with 5 hospitalizations and no deaths.

According to a review of reports submitted to the Foodborne Disease Outbreak Surveillance System from 1998 to 2011, queso fresco or other Mexican-style cheese made with pasteurized milk was implicated in 6 outbreaks of Listeria infections.

It is important to note that the risk of Listeria infections is higher in individuals who are pregnant, aged 65 or older, or have a weakened immune system. In such individuals, it is recommended to avoid consuming meat or cheese from deli counters unless it is reheated to an internal temperature of 165°F or until steaming hot.

Bird flu outbreak in raw milk

The bird flu outbreak in the United States has affected at least 66 people, as well as poultry in all 50 states and dairy cows in 16 states. The outbreak has also been linked to raw milk products, with bird flu fragments found in samples of pasteurized milk and the virus detected in raw milk.

The dangers of raw milk

Raw milk is considered a high-risk food by the U.S. Food and Drug Administration (FDA) due to the potential for contamination with pathogens that can cause illness. The consumption of raw milk has been linked to numerous foodborne illness outbreaks in the past, with the Centers for Disease Control and Prevention (CDC) reporting 202 outbreaks of illnesses linked to drinking raw milk between 1998 and 2018, causing 2,645 people to become sick and 228 to be hospitalized.

Pasteurization

Pasteurization is a process that heats milk to a specific temperature over a certain period of time, killing dangerous viruses and bacteria and making it safe to consume. Nearly all (99%) of the commercial milk supply produced on dairy farms in the U.S. is pasteurized.

Bird flu in raw milk

In late November 2024, California regulators recalled two batches of raw, unpasteurized milk from a Fresno dairy farm after bird flu virus was detected. The dairy subsequently recalled all of its raw milk and cream products, and state regulators placed the farm under quarantine. No human bird flu cases associated with the milk were detected immediately following the recalls. However, public health experts have warned against consuming raw milk during the bird flu outbreak, as the virus has been detected in the milk of infected cows, and there is limited information about whether it may transmit avian flu.

Reducing risks

The FDA advises consumers not to drink raw milk and for producers not to manufacture or sell raw milk or raw milk products, including cheese, made with milk from cows showing symptoms of illness. Pasteurization is a proven process with a long history of protecting public health and is highly effective at eliminating the dangers associated with consuming raw milk.

E. coli outbreak in raw cheddar cheese

An E. coli outbreak linked to raw cheddar cheese was reported by the CDC in March 2024. The outbreak was caused by Raw Farm brand raw cheddar cheese, with seven sick people reporting they had consumed the product in the week before falling ill. The CDC warned against all raw cheese products from the company and recommended that consumers check their refrigerators and freezers for the contaminated cheese and dispose of it. The outbreak investigation has since been closed.

The CDC, public health and regulatory officials, and the U.S. Food and Drug Administration (FDA) collected data to investigate the multistate outbreak of E. coli O157:H7 infections. A total of 11 people across five states were infected with the outbreak strain, with illnesses reported between October 18, 2023, and February 5, 2024. Five people were hospitalized, and two developed hemolytic uremic syndrome, a serious condition that can lead to kidney failure. The true number of sick people was likely much higher, as many recover without medical care and are not tested for E. coli.

The CDC advised people not to consume raw dairy products and instead opt for pasteurized dairy products to reduce the risk of foodborne illnesses. Pasteurization is a process that heats milk to a specific temperature, killing dangerous viruses and bacteria such as E. coli, making it safe for consumption.

Pasteurized cheese outbreak

Between 1998 and 2011, 44 (49%) of the 90 reported cheese-related outbreaks were caused by cheese made with pasteurized milk. These outbreaks caused 1882 illnesses, 230 hospitalizations, and 6 deaths. The most common cheese-pathogen pair was pasteurized queso fresco or other Mexican-style cheese and Listeria (6 outbreaks).

Pasteurized queso fresco or other Mexican-style cheese was also linked to a multistate listeriosis outbreak in 2024, which resulted in 26 illnesses, 23 hospitalizations, and 2 deaths. Another multistate outbreak of foodborne infections caused by unpasteurized cheese occurred in 2024, sickening 11 people across five states.

The process of pasteurization involves heating milk to a specific temperature that kills dangerous viruses and bacteria, including bird flu, E. coli, and salmonella. While pasteurization is effective in eliminating pathogenic microorganisms, cheese can still become contaminated during the cheese-making process or through contact with contaminated equipment, other foods, or infected food workers.

Unpasteurized queso fresco and salmonella

Unpasteurized queso fresco is a type of soft, unaged cheese that has been linked to several Salmonella outbreaks. Between 1998 and 2011, there were 90 reported cheese-related outbreaks in the United States, 38 of which were caused by unpasteurized cheese. Of these 38 outbreaks, 10 were specifically linked to unpasteurized queso fresco or other Mexican-style cheeses contaminated with Salmonella.

Unpasteurized queso fresco is particularly susceptible to Salmonella contamination due to its high moisture and low acidity, which provide favourable conditions for the growth of Salmonella and other pathogenic bacteria. The consumption of contaminated queso fresco can lead to salmonellosis, a foodborne illness that can cause fever, diarrhoea, and abdominal cramps.

To prevent Salmonella outbreaks associated with unpasteurized queso fresco, regulatory interventions such as limiting the illegal importation of cheese, implementing strict sanitation and microbiological monitoring in cheese-making facilities, and controlling food worker contamination are crucial. Additionally, consumer education about the risks associated with consuming unpasteurized dairy products and the importance of proper sanitary procedures for cheese-making is essential.

Furthermore, pasteurization of milk is recognized as one of the most effective public health interventions. Pasteurization involves heating milk to a specific temperature to destroy harmful viruses and bacteria, including Salmonella. While the commercial milk supply in the United States is predominantly pasteurized, the sale and consumption of unpasteurized milk and cheese continue to pose risks to public health.

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