The most common cause of HUS — particularly in children under the age of 5 — is infection with E. coli bacteria that produce certain toxins (shiga toxin-producing E. coli or STEC). One such strain of E. coli is known as E. coli O157:H7. Other strains of E. coli have also been linked to HUS.
E. coli refers to a group of bacteria normally found in the intestines of healthy humans and animals. Most of the hundreds of types of E. coli are normal and harmless. But some strains of E. coli — including those that cause HUS — are responsible for serious foodborne infections.
E. coli can be found in:
- Contaminated meat or produce
- Swimming pools or lakes contaminated with feces
Sometimes, E. coli infection is spread through close contact with an infected person, such as within a family or at a day care center.
Most people who are infected with E. coli, even the more dangerous strains, don't develop HUS.
Other causes of HUS can include:
- The use of certain medications, such as quinine sulfate (Qualaquin), some chemotherapy medications, medications containing the immunosuppressant cyclosporine (Neoral, Sandimmune, Gengraf) and anti-platelet medications
- Certain infections, such as HIV/AIDSor an infection with the pneumococcal bacteria
- Rarely, pregnancy
Susceptibility to an uncommon type of HUS — known as atypical HUS, primary HUS or complement-mediated HUS — can be passed down genetically to children. People who have inherited the mutated gene that causes atypical HUS won't necessarily develop the condition. The mutated gene might be activated after an upper respiratory or abdominal infection.