The bacterium that thrives at a bird's body temperature

Campylobacter is a gram-negative, microaerophilic genus of bacteria. More
than 20 species exist, not all of which make people ill — and **almost 90% of
human Campylobacter illness is caused by Campylobacter jejuni**. Less common
species include C. coli, C. upsaliensis, C. fetus and C. lari.

Why it is a poultry problem

**C. jejuni grows best at 37–42°C. Birds have a body temperature of about
41–42°C**, and carry the bacteria without becoming ill.

That is the whole epidemiology in two sentences. The organism is adapted to
live in a bird, which means healthy poultry are a reservoir rather than a
warning sign — nothing about an infected bird looks wrong.

**Most human infections happen after eating raw or undercooked poultry, or
another food contaminated by it.** People can also be infected **from contact
with dog or cat faeces**. Person-to-person spread is uncommon.

Outbreaks are infrequently reported relative to the number of illnesses —
most cases are isolated, which is what you would expect from a hazard
distributed across every kitchen rather than concentrated in one event.

The good news about handling it

**These bacteria are fragile outside their hosts. They cannot tolerate drying,
and freezing reduces the number on raw meat.**

The illness

Incubation is typically 2–5 days, then:

• Diarrhoea, often bloody
• Abdominal pain
• Fever
• Nausea, sometimes vomiting

More severe illness can occur, including bloodstream infection, and
symptoms that mimic acute appendicitis or ulcerative colitis — which is
how a foodborne infection ends up being investigated as something surgical.

Who gets it, and who gets it badly

Anyone can be infected, but it is more common in **males, children under
5, adults 65 and older, people who work with animals (especially birds or
poultry), and international travellers.**

**At risk of severe disease: adults 65 and older, pregnant women, and people
with weakened immune systems.**

Treatment

Most people recover completely without antibiotics. Where treatment is
needed, **azithromycin and fluoroquinolones are commonly used — but resistance
to fluoroquinolones is common**, which is why the choice is not automatic.

Source: Centers for Disease Control and Prevention.