Food poisoning is a common global issue. It’s often caused by consuming undercooked, expired, inadequately stored, or mishandled food, especially meat and dairy products. These foods can harbour harmful bacteria like Salmonella or E. coli, which can cause symptoms such as nausea, vomiting, and diarrhoea, lasting for several days. However, there is a small chance of suffering even more serious complications.
One example of this is Hemolytic Uremic Syndrome (HUS). This illness is directly related to food poisoning and it can worsen to the point of resulting in kidney failure, which may end up requiring long-term dialysis or transplants. Its impact extends beyond the kidneys, with about half of affected individuals developing complications involving the brain, heart, or muscles. In rare cases, HUS can also lead to diabetes, gallstones, and other long-term health issues. However, a distinction should be made between two types of HUS:
- Typical HUS (STEC HUS): is the focus of this article and it is caused by an infection of Shiga Toxin producing bacteria such a specific strain of Escherichia coli (the O157:H7) or Shigella dysenteriae. A toxin is a harmful substance produced by microorganisms that causes damage to humans’ body.
Atypical HUS is caused by genetic mutations in the complement system, a part of the human immune system responsible for fighting infections. These mutations cause the immune system to mistakenly attack the body’s own cells.
The most concerning aspect of typical HUS is that it disproportionately affects children, making them the most vulnerable group. Children face a higher risk due to their increased exposure to bacteria and their underdeveloped immune systems. Additionally, complications are more frequent and severe in children because of their smaller, immature organs that are more susceptible to damage. This makes early medical attention and support critical for managing infections in young patients.
Understanding the impact of STEC HUS
First, it is important to keep in mind this is a rare disease (see the following article): 1.5 per 100,000 children are affected yearly by food poisoning-derived HUS. Also, the incidence rates are not uniform, they vary greatly depending on the country and age range considered [1].
Still, given the severity of the illness, it is essential to look out for symptoms and attend medical facilities as soon as possible, to avoid further complications. Some symptoms that can help us identify a case of STEC HUS are:
- Ongoing diarrhoea (lasting more than 10 days)
- Blood in stool
- Severe abdominal pain
- Decreased urination
- Vomiting
- Persistent fatigue
- Swelling (edema)
- Seizures
- Confusion or changes in mental state
- High blood pressure
These effects can extend well beyond the acute phase of the illness. Chronic kidney issues, neurological impairments and other health problems can persist for years. These matters require long-term follow-up and care for survivors.
STEC HUS mechanisms, explained
When consuming food contaminated by Escherichia coli, the bacteria can easily travel to the intestines, where they quickly begin to multiply. Not all strains are able to produce Shiga toxin, but those capable will start generating it while the population is growing.
This toxin damages the cells lining the intestines, causing severe diarrhoea and abdominal pain, which can develop into life-threatening conditions like bowel necrosis or perforation. The toxin can also then enter the bloodstream, travelling throughout the body and affecting various organs. One of the primary targets of this toxin is the kidneys, and this is the reason why this illness is particularly damaging to this organ.
In the kidneys, the Shiga toxin causes damage to the small blood vessels, leading to inflammation. This makes it hard for the kidneys to filter waste from the blood, resulting in symptoms such as reduced urine output, high blood pressure, and swelling.
The widespread effects of Shiga toxin can also lead to severe neurological complications: patients may experience symptoms such as seizures, strokes, and long-term cognitive impairments. Cardiovascular issues, including myocarditis (inflammation of the heart muscle), blood clotting and hypertension, can occur as well.
The importance of early diagnosis
When attending the doctor’s office, symptoms like bloody diarrhoea, abdominal pain, decreased urine output and signs of anaemia or bleeding are normally at full display, and they can help recognise this infectious disease. After this, obtaining a diagnosis for STEC HUS is a quick and simple process, and it can help get an early and effective treatment prescription and avoid or minimise long-term complications.
Many tests can be done to obtain a diagnosis, but the standard practice is a stool sample test, to search for the presence of Shiga toxin-producing E. coli, or even Shiga toxin itself. This test only takes 20 minutes, and it can make a big difference in the outcome of the syndrome. Other diagnostic methods include blood tests to identify low blood cell count or high amounts of waste products, that indicate anaemia and kidney dysfunction, respectively. A urine sample test can also be conducted, as well as kidney imaging techniques or even a biopsy to evaluate kidney size, swelling or damage.
However, it may be challenging for many doctors to diagnose HUS because some hospitals in developing countries may lack the equipment and facilities needed for a precise diagnosis.
Preventive Measures for STEC HUS
Preventive Measures are divided into primary and secondary prevention. Primary prevention focuses on preventing bacterial infections. It requires commonly public health recommendations and practices such as:
- Ensure that ground beef is properly cooked so that harmful bacteria is killed. The recommended temperature is 71ºC (160ºF). Feedlot cattle are the most common reservoir of E. coli O157:H7. The bacteria can be present in the intestines of cattle and spread among the meat during processing. If beef is not cooked enough the bacteria can survive and cause infection.
- Pasteurization is an essential primary preventive measure that significantly reduces the number of harmful bacteria in dairy products such as milk or cheese. Consuming unpasteurized dairy products increases the risk of bacterial infections, including STEC HUS.
- Thoroughly wash fruits and vegetables before consuming them. Unfortunately, it’s possible that fruits and vegetables are irrigated with contaminated water or grown in contaminated soil. This increases the risk of harmful bacteria being present on them. Leafy greens (like spinach, lettuce and kale), sprouts and root vegetables are more prone to contamination—so make especially sure to wash these before eating.
- Ensure that water for drinking, cooking and washing is treated and safe. In some geographical areas water can be contaminated with noxious bacteria leading to HUS infection. Juices made from such water can lead to the infection in humans.
- Proper handwashing with soap and water is essential before handling food, after using the bathroom, or following diaper changes.
Other primary prevention measures such as cattle vaccination and proper waste disposal to avoid contaminating soil and water, are effective.
Secondary prevention focuses on early detection and intervention to prevent complications once the infection has occurred. They focus on diarrhoea-associated HUS once it has been diagnosed and include aggressive hydration with electrolytes and monoclonal antibodies against Shiga toxin producing bacteria.
Current treatments and future perspectives
Supportive care remains the primary treatment for HUS, addressing symptoms and complications through careful management of fluid and electrolyte levels, blood pressure, and anaemia. For severe cases, patients may require dialysis to take over the kidneys’ role of filtering waste and excess fluids from the blood. While antibiotics are typically avoided because of their potential to worsen the condition of kidneys and gut, they may be used as well to address secondary infections.
Scientists are working to improve how we detect and diagnose STEC HUS early on so that doctors can differentiate it from other similar illnesses more quickly and accurately. This includes making stool tests better at detecting Shiga toxin and finding signs in the body (called biomarkers) that indicate someone is developing STEC HUS. Researchers are also studying how Shiga toxin affects the body at a cellular level to understand exactly how it causes the disease. They are looking into genetic factors, like specific gene changes and problems in the body’s immune system, that might make some people more likely to develop severe forms of HUS. In addition, scientists are developing new treatments, including ways to neutralize Shiga toxin in the body and create more affordable options to expensive treatments currently available.
Scientists are working to improve how we detect and diagnose STEC HUS early on so that doctors can differentiate it from other similar illnesses more quickly and accurately. This includes making stool tests better at detecting Shiga toxin and finding signs in the body (called biomarkers) that indicate someone is developing STEC HUS. Researchers are also studying how Shiga toxin affects the body at a cellular level to understand exactly how it causes the disease. They are looking into genetic factors, like specific gene changes and problems in the body’s immune system, that might make some people more likely to develop severe forms of HUS. In addition, scientists are developing new treatments, including ways to neutralize Shiga toxin in the body and create more affordable options to expensive treatments currently available.
Just by knowing about the existence of STEC HUS, many cases could be prevented or handled with enough anticipation to prevent long-term complications and fatal outcomes. It is important to act quickly in these situations and allow healthcare professionals to look after the rest. New treatments are on the way, and with awareness and proper handling STEC HUS numbers will drop.