Chronic campylobacteriosis features a long period of sub-febrile temperature and asthenia; eye damage, arthritis, endocarditis may develop if infection is untreated.

Occasional deaths occur in young, previously healthy individuals because of blood volume depletion (due to dehydration), and in people who are elderly or immunocompromised.

[citation needed] Some individuals (1–2 in 100,000 cases) develop Guillain–Barré syndrome, in which the nerves that join the spinal cord and brain to the rest of the body are damaged, sometimes permanently.

[3] In patients with HIV, infections may be more frequent, may cause prolonged bouts of dirty brown diarrhea, and may be more commonly associated with bacteremia and antibiotic resistance.

[citation needed] C. jejuni can also cause a latent autoimmune effect on the nerves of the legs, which is usually seen several weeks after a surgical procedure of the abdomen.

The effect is known as an acute idiopathic demyelinating polyneuropathy (AIDP), i.e. Guillain–Barré syndrome, in which one sees symptoms of ascending paralysis, dysaesthesias usually below the waist, and, in the later stages, respiratory failure.

[citation needed] Some strains of C jejuni produce a cholera-like enterotoxin, which is important in watery diarrhea observed in infections.

In a small number of cases, the infection may be associated with hemolytic uremic syndrome and thrombotic thrombocytopenic purpura through a poorly understood mechanism.

[citation needed] The common routes of transmission for the disease-causing bacteria are fecal-oral, person-to-person sexual contact,[citation needed] ingestion of contaminated food (generally unpasteurized (raw) milk and undercooked or poorly handled poultry), and waterborne (i.e., through contaminated drinking water).

[citation needed] A different approach, propagated within the EU is that Campylobacter mitigating measures should be undertaken mainly at the primary production level.

[14] About 15 of every 100,000 people are diagnosed with campylobacteriosis every year, and with many cases going unreported, up to 0.5% of the general population may unknowingly harbor Campylobacter in their gut.

[15] A large animal reservoir is present as well, with up to 100% of poultry, including chickens, turkeys, and waterfowl, having asymptomatic infections in their intestinal tracts.

[16] In August–September 2016, 5,200 people fell ill with campylobacteriosis in Hastings, New Zealand, after the local water supply in Havelock North tested positive for the pathogen Campylobacter jejuni.

[19] It is suspected that after heavy rain fell on 5–6 August, water contamination from flooding caused the outbreak, although this is the subject of a government Inquiry.

All schools in Havelock North closed for two weeks, with the Hastings District Council advising an urgent notice to boil water for at least one minute before consumption.

[citation needed] According to Centers for Disease Control and Prevention, a multistate outbreak of human Campylobacter infection has been reported since 11 September 2017.

In all, 55 cases were reported from 12 states (Florida, Kansas, Maryland, Missouri, New Hampshire, New York, Ohio, Pennsylvania, Tennessee, Utah, Wisconsin and Wyoming).