April 7 2015 World Health Day (United Nations)

In 1948, the First World Health Assembly proposed the establishment of a World Health Day to commemorate the founding of the World Health Organization and to urge governments, organizations and companies to invest in health and build a future safer.

World Health Day 2015: How Scientists Track Food Poisoning

There are so many types of pathogens causing food poisoning, from viruses, to bacteria, to parasites, in addition to toxins, pollutants, and heavy metals. In the U.S., food poisoning affects about 1 in 6, or 48 million people each year,hospitalizing 128,000 and killing 3000. The burden is far greater globally, withfood and waterborne diarrheal illnesses killing 2 million people annually, 40% of them children. There is a large economic toll to farmers and industry as well, estimated at more than $75 billion per year.

The top numbers of cases here are from norovirus, Salmonella, Clostridium perfringens, and Campylobacter. In addition to Salmonella, Toxoplasma, E. coli O157, and Listeria tend to cause more serious infections and death. This new strain of Shigella has potential to be very serious, since as few as 10 bacteria can cause serious infection, with bloody diarrhea requiring hospitalization, and oral antibiotics will be ineffective.

Have you wondered how the outbreaks are traced and solved? I’ve always found this aspect of infectious diseases and epidemiology fascinating.

Identifying the problem

It’s not always easy to identify the cause of an illness, especially if there is just an isolated case, which is true 95% of the time. Most of the time, physicians don’t order stool cultures, hoping the illness will be self-limited. A routine stool culture will miss many

pathogens anyway—the lab has to be alerted to use special media for some organisms, like Vibrio from shellfish, for example, and rarely will send samples to a reference lab for norovirus. Studies for parasites are also commonly sent to reference labs, taking days for results. Because it takes days to identify a pathogen, patients may be treated empirically—by guess and by gosh—based on typical patterns. This encourages overuse of antibiotics like Cipro and Bactrim, fueling resistance, and is part of what makes this recent Shigella outbreak scary.

If there is a cluster of cases, health department workers will begin byinterviewing patients looking for commonalities in exposures. If the affected person is a food or daycare worker, they will likely be prohibited from working until their infection is cleared.

State public health labs join the investigation, doing serotyping of bacteria to identify a specific bacterial strain, or pulse-field gel electrophoresis (PFGE) for DNA fingerprinting, which identifies the specific genetic pattern of a given bacteria, and can detect identical isolates.  State health departments share results through a large database, PulseNet, helping to solve multi-state outbreaks.

Data from interviews are analyzed, looking for commonalities. It is very difficult to tease out the source of illness, as it may be an ingredient, like a spice, rather than a specific food, like hamburger or cheese. One useful tool is the grocery shopper’s rewards cards, which track all purchases. Health departments can use this Salmonella from contaminated spices from India, so it is unsurprising that the specific food causing an illness is identified in only about half of outbreaks. Illustrating the complexity is an outbreak of enterohaemorrhagic Escherichia coli (EHEC) outbreak in Europe in 2011, linked to contaminated fenugreek seeds imported from Egypt, which led to almost 4000 cases of EHEC infection in 16 countries, with more than 900 cases complicated by haemolytic uraemic syndrome (HUS) cases and 55 deaths. The estimated loss for farmers and industries was $1.3 billion. This outbreak was initially thought to be due to cucumbers, costing Spanish growers $200 million per week before the source was correctly identified.

information to identify possible food sources and other people at risk of disease. Often, investigations have to include tracebacks through multiple processors and suppliers, many of whom might be overseas, as happened with the cases of

While globalization now brings us wonderful fruits and vegetables year round, it also makes tracing more difficult and spreads multidrug resistance, as with the Shigella, as well.

How does food get contaminated?

Contamination can happen anywhere along the food chain. During production, problems can occur from chickens laying Salmonella infected eggs or from deer droppings contaminating fruit that has fallen from trees (unpasteurized apple cider anyone?) or strawberries in fields, for example. Irrigation water might be contaminated by workers who lack adequate sanitation dust laden with cattle excrement, spread from factory farms and carrying antibiotic resistant bacteria.

facilities on the job, or by livestock or wild animals wandering through a field, or spread by

Problems have occurred during processing, as well, if the food is stored in unclean conditions, or during animal slaughter, during distribution, or during the final food preparation. Sometimes, foods like milk are adulterated—remember the China melamine scandal that sickened almost 300,000 and killed a number of babies? This week, it is human breast milk diluted with cow’s milk, which might cause serious allergies.

While we have always been admonished to wash fruits and vegetables, we’ve learned that it often doesn’t work well with those with many crevices, like raspberries. We now know that plants can take up some pathogens from the soil or through pores in their leaves, a process known as “internalizing” them. Although this doesn’t appear to be a very common way of transmitting infection, this did appear to be the source of infection in an outbreak of Salmonella from mangoes. A hot water dip to control fruit flies was followed by a cold water bath, during which pathogens were thought to be drawn into the fruit by changes in hydrostatic forces within the fruit, caused by the sudden temperature change. Interestingly, Europeans who had mangoes from the same farm did not become ill—mangoes exported to Europe did not undergo the hot water dip.

Recent foodborne outbreaks

Highlights of the year, from an epidemiology perspective are this spring’sListeria outbreak from Blue Bell Creameries’ ice cream. Listeria monocytogenes is a bacteria that can cause meningitis and blood stream infections, and is particularly deadly in pregnancy or immunocompromised patients. Unpasteurized cheeses and deli meats are other common sources of Listeria infection.

Israeli Defense Forces were sidelined when 250 paratroopers were sickened after a Sabbath dinner, likely due to spoiled chicken. Even flour was recently recalled for possible Salmonella contamination, though no one became ill.

No self-respecting Infectious Diseases physician could write about food safety and not say, “Don’t drink raw milk!” It can transmit a variety of infections, including Brucella, Listeria, Mycobacterium bovis, Salmonella, and Shiga toxin-producing Escherichia coli, including E. coli O157, as it just did in aCalifornia outbreak of Campylobacter.

While not so recent, one of my favorite epi mystery stories was how an Orthodox Jewish family came down with an infection from pork tapeworm.

Food safety

In response to years of outbreaks, like Salmonella-tainted peanut butter, and the growing complexity of the food supply chain, the Food Safety Modernization Act (FSMA) was passed in 2011, making the FDA responsible for a huge overhaul of the monitoring and regulatory system. There is a major change in focus from reactive, enforcement provisions to shifting to preventive efforts, including requiring food production facilities to have a hazard analysis plan and risk-based assessment for preventive efforts. A number of the details are still being worked out, with major sticking points apparently being the effect on small farms and on craft breweries.