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This finding suggests suggests evolutionary biology and virology together can accelerate the discovery of viral-defence mechanisms, according to researchers at Fred Hutchinson Cancer Research Center.

These findings by Julie Kerns, Ph.D., a postdoctoral researcher in the Hutchinson Center’s Basic Science Division, published Jan. 25 in the open-access journal PLoS Genetics, present a striking example by which evolutionary studies can directly lead to biomedically important discoveries in the field of infectious diseases.

The immunity gene, called ZAP, is a key player in a newly discovered branch of antiviral defences in mammals referred to as ‘‘intrinsic immunity.’’ Host proteins like ZAP can target intracellular stages of the viral life cycle to inhibit viral activity. The ZAP gene, first discovered in rats, thwarts a variety of divergent viruses, from retroviruses (like HIV) to alphaviruses (like Sindbis) to filoviruses (like Ebola).

Researchers believe ZAP functions by virtue of its RNAbinding abilities, which recognize specific sequences of the virus and target their viral RNA for destruction. Host-virus interactions are a classic example of genetic conflict in which both entities try to gain an evolutionary advantage over the other. This ‘‘back-and-forth’’ evolution is predicted to result in rapid changes of both host and viral proteins, which
results in an evolutionary signature of positive selection, especially at the direct interaction interface.

“This suggests that we might be able to deduce host-virus conflicts purely by looking at rapidly evolving protein segments,” said Kerns, the lead author of the study, which was conducted in collaboration with senior author Harmit Singh Malik, Ph.D., of the Center’s Basic Sciences Division and also co-author Michael Emerman, Ph.D., of the Center’s Human Biology Division Department.

The researchers found that there has been very little sequence evolution in the RNA-binding domain, which
suggests that human ZAP may be similar to the rat gene in its viral RNA-binding specificity.

Surprisingly, the rapid evolution characteristic of “intrinsic immunity” genes was concentrated in a protein domain that was not even present in the originally discovered rat gene.

The authors found that humans encode two protein versions, or isoforms, from a single ZAP gene: a shorter version similar to the original rat gene and a longer version that possesses a rapidly evolving poly (ADP-ribose) polymerase (PARP)-like domain.

In virological assays, the longer human ZAP protein isoform has higher antiviral activity. Thus, positive selection correctly predicted the more potent antiviral isoform of this protein.

The authors further suggest that ZAP is locked in a conflict with alphaviruses. The discovery of a potential human gene that can restrict alphaviral infection is particularly timely as the mosquito-borne alphavirus, Chikungunya, was responsible for a large epidemic in parts of Southeast Asia in 2006 and is now threatening to invade certain parts of Europe.

The researchers believe that this finding has an enormous implications for the understanding of intrinsic immunity against viruses. This could potentially serve as a guide in the development of antiviral therapeutics.

“We think that a particular alphaviral protein may be playing an evolutionary ‘cat-and-mouse’ game with the ZAP gene,” Malik said. “Identifying this protein could lead to novel ways to tackle diseases caused by alphaviruses.”

Source http://www.fhcrc.org

I just hope we see more technical people in senior levels - safety should be in the same light as profits.

Another person whihc now totals 13 has come down with the deadly Legionnaires’ disease and health officials say the bacteria that causes the deadly respiratory ailment has been found at a second location, a Syracuse nursing home in NY.

So far investigators searching for the potential source of the outbreak have discovered that the Legionella bacteria that causes the illness in the water system of the 526-bed Van Duyn Home and Hospital, said Gary Sauda, the Onondaga County director of environmental health.

Legionnaires’ is a severe form of pneumonia. People become infected by inhaling airborne water droplets that contain the bacteria. It can be fatal if left untreated.

So far one person has died since the outbreak began June 30, although health officials said they have not yet confirmed Legionnaires’ was the cause of the person’s death.

Investigators suspect the outbreak was caused by Legionella bacteria discovered in one of the air conditioning cooling towers at Community General Hospital, but they have not yet proven it. Six of 13 people infected were Community General patients.

In Legionnaires’ outbreaks, people up to two miles away from the source can be infected. The nursing home and hospital are located less than a half mile apart.

The staff at Van Duyn is working with state health department officials to minimize risks to the nursing home’s residents, Sauda said.

On Wednesday, officials at Community General reported that their first effort to kill the Legionella bacteria in its cooling towers two weeks ago did not work. The hospital performed a 24-hour disinfection process July 4. The hospital received test results Tuesday showing the bacteria was still present.

At that point, the hospital had already carried out a second 48-hour disinfection process over the weekend, following federal Centers for Disease Control and Prevention guidelines, said Tom Quinn, the hospital’s president and chief executive officer.

Test results from the second cleaning may not be available for two weeks, he said.

Source

Onchocerciasis is an infection caused by Onchocerca volvulus, a parasite nematode worm transmitted to humans by a species of black fly of the Simulium genus whose larvae develop in fast-flowing rivers.

Infected subjects suffer not only from severe skin lesions but also eye damage that can lead to irreversible of−loss of sight, hence the name ‘river blindness’. A huge majority (99%) of the 37 million people
infected by the parasite live in SubSaharan. Ivermectin, a medicine capable of killing the parasite
embryos (the microfilariae) circulating in the organism of patients and temporarily interrupting the nematode’s reproduction, is the only treatment used for onchocerciasis control.

Since 1995, the African Programme for Onchocerciasis Control (APOC) has been covering 19 of the
continent’s 28 countries hit by the disease. Access to this treatment is possible for 70 million people and has
significantly diminished the onchocerciasis-induced morbidity. However, the doubling of cases of infection in
certain communities of Ghana between 2000 and 2005, in spite of annual treatments, created fear of the emergence of ivermectin-resistant strains. Such apprehension appears particularly justified in that a high degree of therapeutic cover is achieved during mass distribution campaigns and hence only a tiny part of the parasite population targeted remains unexposed to drug treatment pressure.

Since 1994, a team of IRD researchers, working jointly with Cameroon researchers and others from McGill University of Montreal, has been monitoring a cohort of Cameroon patients benefiting from repeated treatments with ivermectin. Regular parasite sampling from these subjects was performed over a 13-year period in order to determine the changes in the genetic structure of Onchocerca volvulus
populations. Each occasion involved measurement of the genotype frequency of heterozygotes and homozygotes for the gene coding β-tubulin, a protein involved in the organization of the parasite’s cells. The team focused on this particular gene because it acts as a marker of resistance to ivermectin in other nematode species parasitic on cattle. As a control, they monitored the changes in genotype frequency
of two other genes, known for their high evolutionary stability over time. The proportion of homozygotes and heterozygotes for these two genes remained stable throughout the investigation, but the situation was
completely different for the β-tubulin gene.

Between 1994 and 1998, the percentage of parasites showing a genotype homozygous for this gene fell from 79 to 31% in subjects receiving quarterly treatment with ivermectin. At the same time, the proportion of heterozygous genotypes changed in the opposite sense, rising from 21 to 69%. These results could be the sign of adaptation of nematode worm populations to repeated treatments using this drug. The research team inferred that the parasites showing a genotype homozygous for β-tubulin are more susceptible to
it. As courses of treatment progressed, they would therefore gradually disappear, to the benefit of the more resistant heterozygous strains. Ivermectin’s effect on microfilariae, other than its direct one, is to prevent them from leaving the uterus of adult worms, for several months after treatment: this is its embryostatic effect. Post-treatment, there were more microfilariae in the uterus of homozygous female parasites than in those of heterozygous females.

This could mean that, in the latter, the microfilariae succeed in leaving the uterus, as they usually do in the absence of treatment, and therefore that the embryostatic effect of ivermectin would be diminished. Contrary to the effect anticipated, the repeated exposure to treatments could in this way select those worms more able to keep up the production of new generations. Nevertheless, the drug’s direct action on the moment, there is no reason to call into question the current control strategy against the disease based on annual treatments with ivermectin.

Affirmation of the results requires further investigations1, starting from new cohorts subjects infected by Onchocerca volvulus who have not yet been treated with ivermectin. This type of approach should bring more information on the risks of the parasite’s resistance to this drug. If such risks were confirmed, then the whole onchocerciasis control strategy would probably have to be revised. Nevertheless, for many years to come, ivermectin could well remain the sole drug applicable for mass treatment in measures to control river blindness.

Healthy consumers can handle the low levels of bacteria occasionally found in cosmetics. But for severely ill patients these bacteria may trigger life-threatening infections, as patients in the intensive care unit at one Barcelona hospital discovered after using contaminated body moisturiser. The Burkholderia cepacia bacteria outbreak is detailed in the open access journal, Critical Care.

Five patients suffered from infection including bacteremia, lower respiratory tract infection and urinary tract infection associated with the bacterial outbreak in August 2006. Skin care products sold in the European Union are not required to be sterile, but there are limits to the amount and type of bacteria that are permitted. The Hospital Universitari del Mar, Universitat Autònoma de Barcelona’s routine infection control surveillance pinpointed the unwelcome bacteria in five patients’ biological samples.

Researchers tested a number of environmental samples, and discovered that moisturizing body milk used in the patients’ care was a B. cepacia reservoir. Pulsed-field gel electrophoresis experiments confirmed that all of the strains of B. cepacia bacteria found in patient and environmental samples were from the same bacterial clone. Tests on sealed containers of the moisturizer confirmed that the bacteria had not invaded the product after it had been opened, but that it was contaminated during manufacturing, transportation or
storage.

“This outbreak of nosocomial infection caused by B. cepacia in five severely ill patients supports a strong
recommendation against the use cosmetic products for which there is no guarantee of sterilization during the manufacturing process,” says study author Francisco Álvarez-Lerma. B. cepacia is a group or “complex” of bacteria that can be found in soil and water. They have a high resistance to numerous antimicrobials and antiseptics and are characterised by the capacity to survive in a large variety of hospital microenvironments These bugs pose little medical risk to healthy people. However, those with weakened immune systems or chronic lung diseases, particularly cystic fibrosis, may be more susceptible to B. cepacia infection. B
cepacia is a known cause of hospital infections.

Moisturizing body milk as a reservoir of Burkholderia cepacia: outbreak of nosocomial infection in a multidisciplinary intensive care unit. Francisco Alvarez-Lerma, Elena Marull, Roser Terradas, Concepcion Segura, Irene Planells, Pere Coll, Hernando Knobel and Antonia Vazquez. Critical Care (in
press).

Finding should aid those developing anti-virus vaccines. Vaccines have led to many of the world’s greatest public health triumphs, but many deadly viruses, such as HIV, still elude the best efforts of scientists to develop effective vaccines against them.

An improved understanding of how the immune system operates during a viral infection is critical to designing successful anti-virus vaccines. Scientists from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), have added an important dimension to this knowledge.

Focusing on mouse lymph nodes—bean-shaped organs that contain a variety of immune cells and are distributed throughout the body—the researchers discovered that immune cells confront viruses just inside of the lymph node and not deep within these organs as previously thought. The study, led by Jonathan Yewdell, M.D., Ph.D., chief of the NIAID Cellular Biology Section and his NIAID colleague, Heather Hickman, Ph.D., is described in a report online in Nature Immunology.

The results are significant, the authors say, as they observed in detail the interaction of viruses and immune cells inside a living organism, in this case, mice. Combining expertise from disciplines such as imaging, immunology, virology and other specialties, the scientists first extracted and then purified specific T cells—killer T cells—from mice. Killer T cells, which attack and kill infected or cancerous cells, are major
weapons in the immune system arsenal. The scientists labelled the T cells with a fluorescent marker, injected them back into the mice, and then infected the animals with vaccinia virus, the virus used to make smallpox vaccine, engineered to express a brilliantly coloured protein.

Using a multiphoton microscope, a highly specialized microscope that enables scientists to peer into a living
organism, the scientists could now look into the lymph nodes of the infected mice and see that the viruses had infected cells just inside the lymph node surface, triggering a swarm of T cells. These virus-specific T cells form an elaborate and dynamic communications network that activates them to divide and travel to the site of viral infection, where they kill virus-infected cells.

“A key challenge in viral vaccine research is developing strategies for immunizing against lethal viruses such as HIV that have eluded the standard vaccine approaches,” notes Dr. Yewdell. “We have contributed a page to the handbook of understanding how to rationally design vaccines to elicit a T-cell response.” According to the NIAID team, pinpointing where in the lymph node immune cells fight the virus should help efforts to design effective anti-virus vaccines.

Listeria appears again - but this time in sandwiches wwhere it was sold to 20 people at Middlemore Hospital in New Zealand.

These pre-packaged Thai chicken sandwiches were sold on Monday at the hospital’s Aviary Cafe, which is mainly used by staff.

The contamination was detected in routine listeria testing where the results were given to the hospital yesterday.

It was not known last night whether other sandwich varieties at the cafe were infected, or if other products from the sandwiches’ supplier, Naturezone, were infected with listeria and had been distributed to other outlets.

The bacterium can be fatal to people with low immune systems and can cause miscarriages or stillbirths if it infects pregnant women.

A spokeswoman for Spotless Services, the company that runs the cafe, said it was not yet known how many of its outlets had been stocked with the sandwiches. Naturezone could not be reached for comment last night.

Auckland Regional Public Health Service spokesman Dr Greg Simmons said last night that greatly improved methods of testing were bringing the listeria cases to the surface.

All positive tests in the past three weeks had come from the same testing facility.

“We are conducting a thorough site inspection at the company and we will ensure extensive product and environmental testing to identify the source,” Dr Simmons said

Despite the relatively low risk, he said, it was a serious situation.

“We are concerned that a whole lot of ready-to-eat products look like they are being contaminated. We would be silly not to be concerned.”

The bacterium usually produces fever, diarrhoea and general unwellness within three weeks of infection, although it can take as long as 10 weeks for symptoms to show.

Here is the draft policy (Sec. 555.320) for Listeria monocytogenes in Ready To Eat (RTE) Foods.

This draft guideline, when finalized, will represent the Food and Drug Administration’s (FDA’s) current thinking on this topic. It does not create or confer any rights for or on any person and does not operate to bind FDA or the public. You can use an alternative approach if the approach satisfies the requirements of the applicable statutes and regulations. If you want to discuss an alternative approach, contact the FDA staff responsible for implementing this guidance. If you cannot identify the appropriate FDA staff, call the appropriate telephone number listed on the title page of this guidance.

INTRODUCTION:
The purpose of this Compliance Policy Guide is to provide guidance to FDA Staff on FDA’s enforcement policy for Listeria monocytogenes (L. monocytogenes) in foods.

FDA’s guidance documents, including this guidance, do not establish legally enforceable responsibilities. Instead, guidances describe the Agency’s current thinking on a topic and should be viewed only as recommendations, unless specific regulatory or statutory requirements are cited. The use of the word should in Agency guidances means that something is suggested or recommended, but not required.

BACKGROUND:
L. monocytogenes is a pathogenic bacterium that is widespread in the environment and may be introduced into a food processing facility. L. monocytogenes can contaminate foods and cause a mild illness (called listerial gastroenteritis) or a severe, sometimes life-threatening, illness (called invasive listeriosis). Foods that have been implicated in outbreaks of invasive listeriosis have been foods that are ready-to-eat (RTE).

RTE foods can be contaminated if ingredients in the foods are contaminated with L. monocytogenes and are not treated to destroy viable cells of this pathogen, or if L. monocytogenes is allowed to contaminate the RTE food because of improper sanitary conditions or practices. Most RTE foods do not contain detectable numbers of L. monocytogenes. For many RTE foods, contamination with L. monocytogenes can be avoided – e.g., through the application of current good manufacturing practice requirements that establish controls on ingredients, listericidal processes, segregation of foods that have been cooked from those that have not, and sanitation. Sanitation controls include effective environmental monitoring programs designed to identify and eliminate L. monocytogenes in and on surfaces and areas in the plant.

In 2003, FDA and the Food Safety and Inspection Service of the United States Department of Agriculture, in consultation with the Centers for Disease Control and Prevention of the United States Department of Health and Human Services, released a quantitative assessment (the Risk Assessment) of relative risk associated with consumption of certain categories of RTE foods that had a history of contamination with L. monocytogenes, or that were implicated epidemiologically with an outbreak or a sporadic case of listeriosis. The Risk Assessment estimated that the risk of listeriosis would vary widely among these food categories.

According to the Risk Assessment, foods estimated to pose the highest risk of being associated with listeriosis are RTE foods that support the growth of L. monocytogenes. Examples of RTE foods that support the growth of L. monocytogenes include:

Milk;
High fat and other dairy products (e.g., butter and cream);
Soft unripened cheeses (greater than 50 percent moisture) (e.g., cottage cheese and ricotta cheese);
Cooked crustaceans (e.g., shrimp and crab);
Smoked seafood (e.g., smoked finfish and mollusks);
Raw seafood that will be consumed as sushi or sashimi;
Many vegetables (such as broccoli, cabbage, and salad greens);
Non-acidic fruit (such as melon, watermelon, and papaya); and
Some deli-type salads and sandwiches (particularly those containing seafood and those prepared at retail establishments without acidification and/or the addition of antimicrobial substances).

In contrast, the foods estimated to pose the lowest risk of being associated with listeriosis are foods that, because of intrinsic factors, extrinsic factors, and/or processing factors do not support the growth of L. monocytogenes. Intrinsic factors include chemical and physical factors that are normally within the structure of the food, e.g., pH and water activity. Extrinsic factors are those that refer to the environment surrounding the food, e.g., storage temperature. Processing factors include substances added to adjust the pH of food (e.g., acids) and substances that, alone or in combination with other substances, have antimicrobial properties (e.g., sorbates and benzoates). It is well established that L. monocytogenes does not grow when:

The pH of the food is less than or equal to 4.4;
The water activity of the food is less than or equal to 0.92; or
The food is frozen.

Foods may naturally have a pH or water activity that prevents growth of L. monocytogenes or processing factors may be deliberately used to achieve those characteristics (e.g., by adding acid to deli-type salads to bring the pH to less than or equal to 4.4). At pH values above 4.4, processing factors generally are used in combination to prevent the growth of L. monocytogenes (e.g., sorbates or benzoates may be used in combination with organic acids such as acetic acid, lactic acid, and citric acid in foods such as deli-type salads). The effectiveness of a particular listeristatic control measure in preventing growth in a particular RTE food generally is determined case-by-case, for example, using the results of growth studies specific to the food matrix.

Examples of RTE foods that generally are considered to not support the growth of L. monocytogenes include:

Fish that are preserved by techniques such as drying, pickling, and marinating;
Ice cream and other frozen dairy products;
Processed cheese (e.g., cheese foods, spreads, slices);
Cultured milk products (e.g., yogurt, sour cream, buttermilk);
Hard cheeses (less than 39 percent moisture) (e.g., cheddar, colby, and parmesan);
Some deli-type salads, particularly those processed to a pH less than 4.4 and those containing antimicrobial substances such as sorbic acid/sorbates or benzoic acid/benzoates under conditions of use documented to be effective in preventing the growth of L. monocytogenes;
Some vegetables (such as carrots); and
Crackers, dry breakfast cereals, and other dry foods.

Fruits, vegetables, and cheeses (e.g., soft and semi-soft cheeses) not listed in this CPG may include some products that support growth as well as other products that do not support growth.

POLICY:
FDA will review the available evidence on a case-by-case basis to determine if a food is a RTE food that supports growth or a RTE food that does not support growth.

Ready-to-Eat Food

“Ready-to-eat food” (RTE food) means a food that is customarily consumed without cooking by the consumer, or that reasonably appears to be suitable for consumption without cooking by the consumer.

A food may be considered to be suitable for consumption without cooking by the consumer, and thus a RTE food, even though cooking instructions are provided on the label. For examples, fresh and frozen crabmeat and individually quick frozen (IQF) peas and corn may be RTE foods. Some consumers eat such products without cooking, because they appear to be ready-to-eat.

Ready-to-Eat Foods that Support Growth of L. monocytogenes

Generally, we intend to consider that a RTE food will support the growth of L. monocytogenes if it does not meet the characteristics of a RTE food that does not support growth, as indicated in section III.C.

FDA may regard a RTE food that supports growth of L. monocytogenes to be adulterated within the meaning of section 402(a)(1) of the Federal Food, Drug, and Cosmetic Act (the Act; the FD&C Act) (21 U.S.C. 342(a)(1)) when L. monocytogenes is present in the food based on the detection method indicated in section IV.A.

Ready-to-Eat Foods that Do Not Support Growth of L. monocytogenes

A RTE food does not support the growth of L. monocytogenes if the food:
Has a pH that is less than or equal to 4.4; or
Is customarily held and consumed in a frozen state; or
Has a water activity that is less than 0.92; or
Is processed using an effective listeristatic control measure (e.g., an antimicrobial substance or a combination of factors such as pH, water activity, and antimicrobial substances).

FDA may regard a RTE food that does not support the growth of L. monocytogenes to be adulterated within the meaning of section 402(a)(1) of the Act (21 U.S.C. 342(a)(1)) when L. monocytogenes is present at or above 100 colony forming units per gram of food (cfu/g)

REGULATORY ACTION GUIDANCE:
Ready-to-Eat Foods that Support Growth of L. monocytogenes

The following represents criteria for recommending legal action to CFSAN/Office of Compliance/Division of Enforcement (HFS-605):
L. monocytogenes is detected in one or more subsamples of a RTE food that supports the growth of L. monocytogenes.

Use Bacteriological Analytical Manual Online, Chapter 10 - “Listeria monocytogenes,” “Detection and Enumeration of Listeria monocytogenes in Foods” as the method for detecting and confirming presence of L. monocytogenes (available at http://www.cfsan.fda.gov/~ebam/bam-10.html).

Ready-to-Eat Foods that Do Not Support Growth of L. monocytogenes

Consult with CFSAN/Office of Compliance/Division of Enforcement (HFS-605) before recommending legal action for RTE foods that do not support the growth of L. monocytogenes. Use ISO 11290-2:1998(E) “Microbiology of food and animal feeding stuffs - Horizontal method for the detection and enumeration of Listeria monocytogenes - Part 2: Enumeration method” as the method for enumerating L. monocytogenes. (ISO 11290-2:1998/Amd. 1:2004(E) “Microbiology of food and animal feeding stuffs - Horizontal method for the detection and enumeration of Listeria monocytogenes - Part 2: Enumeration method AMENDMENT 1: Modification of the enumeration medium” amends ISO 11290-2:1998(E). The amendment uses ALOA agar instead of PALCAM agar. If ALOA agar is not commercially available in the United States, use PALCAM according to ISO 11290-2:1998(E)). ISO methods are available from the International Organization for Standardization at http://www.iso.org/iso/en/ISOOnline.frontpage.

Use rapid biochemical test kits according to the Bacteriological Analytical Manual Online, Chapter 10 – “Detection and Enumeration of Listeria monocytogenes in Foods” Section E-11 (available at http://www.cfsan.fda.gov/~ebam/bam-10.html), instead of ISO 11290-2:1998(E) Section 9.5, for confirmation of L. monocytogenes isolates.

Foods that are Not RTE Foods
Consult with CFSAN/Office of Compliance/Division of Enforcement (HFS-605) when L. monocytogenes is present in a food that is not a RTE food.

Other Considerations

The criteria in this guidance do not establish an acceptable level of L. monocytogenes in food. FDA may choose to take legal action against adulterated food that does not meet the criteria for recommending legal action to CFSAN.

Further, the criteria in this guidance do not excuse violations of the requirement in section 402(a)(4) of the Act (21 U.S.C. 342(a)(4)) that food may not be prepared, packed, or held under insanitary conditions or the requirements in FDA’s good manufacturing practices regulation (21 CFR part 110). As set out in 21 CFR 110.80, food manufacturers must take “[a]ll reasonable precautions … to ensure that production procedures do not contribute contamination from any source.”

SPECIMEN CHARGES:
Domestic Seizure

The article of food was adulterated when introduced into and while in interstate commerce and is adulterated while held for sale after shipment in interstate commerce within the meaning of the Act, 21 U.S.C. 342(a)(1), in that it bears and contains a poisonous or deleterious substance, namely Listeria monocytogenes, which may render it injurious to health.

Import Detention
The article of food is subject to refusal of admission pursuant to section 801(a)(3) of the FD&C Act in that it appears to be adulterated within the meaning of section 402(a)(1) of the FD&C Act in that it bears and contains a poisonous or deleterious substance, Listeria monocytogenes, which may render it injurious to health.

Public health officials in the U.S. are investigating a major outbreak of listeria and have found up to 16 samples with the listeria bacteria at a milk processing plant.

The outbreak has resulted in the deaths of 3 elderly men who have died since June after drinking pasteurized milk that was contaminated with the bacteria.

The same strain of listeria also sickened a pregnant woman, who then miscarried and a second woman also was sickened after drinking milk from the plant.

The dairy processing plant in Shrewsbury is 35 miles west of Boston in Massachusetts, and is owned by Whittier Farms.

While officials have yet to determine exactly how the milk was contaminated, one environmental swab, one skim milk sample and seven flavored milk samples tested positive for the same strain of listeria that is now being blamed for the outbreak that sickened people.

The milk appears to have been contaminated during the production process and could have been lurking somewhere within the machinery. Experienced microbiologists are currently on site to determine the cause of the outbreak and to find potential reservoirs of the deadly micro-organisms.

So far, no further cases have been reported and health officials maintain that the health risk to the public is low.

The processing plant distributes milk under various brand names to stores across central Massachusetts and also operates a 500-acre farm in the town of Sutton.

Officials say the plant has been closed since December and will remain so while investigations continue and the bacterium is completely eradicated.

Here’s what they say on their site:

“Whittier Farms Inc. was notified today by the Department of Public Health that a press release would be issued today informing the public that Whittier Farms Inc. is being linked to cases involving listeria. Whittier Farms is fully cooperating with this investigation and will continue to do so.”

Listeriosis is a type of food poisoning that can be particularly dangerous to the elderly, infants, pregnant women and people with low immune system such as those chronic medical conditions; the symptoms include fever, abdominal cramps, headache, stiffness, nausea and diarrhea.