Q Fever (Coxiella burnetii)

Clinical Summary

It’s caused by the bacterium Coxiella burnetii, primarily found in sheep, goats, cattle and their birthing products.

Many people infected never become ill, but those who do often get flu-like symptoms: fever, chills, fatigue, muscle aches. 

The disease can progress to pneumonia, hepatitis, and in rare cases a chronic form may involve heart or vascular infection (endocarditis).

The main route of human infection is inhaling dust or aerosols contaminated with animal waste or birth materials; unpasteurized milk is a minor route.

Treatment for symptomatic acute cases uses the antibiotic doxycycline; chronic cases require prolonged combination therapy and are more difficult to manage.

Clinical Links & Info

What It Is

Q fever is caused by the bacterium Coxiella burnetii, which naturally infects animals such as goats, sheep, and cattle. 

The bacterium is shed in animal birth products (placenta, amniotic fluid), urine, feces, and milk of infected animals. 

Humans most often get infected by inhaling dust contaminated with those animal materials; direct contact or ingestion of raw milk may also be routes. 

The disease is found worldwide and is considered a zoonosis (animal-to-human transmitted disease). 

Many infected people show no symptoms; infection doesn’t always lead to illness. 

Types

Acute Q fever – the initial illness that follows recent infection; may be mild or more severe, but typically presents soon after exposure. 

Chronic Q fever – develops months or even years after the initial infection in a minority of cases; often life-threatening if untreated. 

Chronic Q fever commonly involves endocarditis (infection of heart valves) but may also involve bone, liver, vascular aneurysms, or other organs.

Risk for chronic progression is higher in persons with heart valve defects, vascular grafts, aneurysms, immune suppression, or pregnant women.

Many people infected never become ill (asymptomatic), so types overlap with the spectrum of illness from no symptoms → acute → chronic. 

Signs and Symptoms

For those who become ill, initial symptoms often resemble influenza: fever, chills, fatigue, muscle aches, and headache. 

Some people develop cough (often dry), chest pain, nausea, vomiting, or diarrhea; liver inflammation (hepatitis) and lung involvement may occur.

The incubation period (time from exposure to symptoms) is generally about 2–3 weeks.

A small percentage (< 5 %) of infected persons can go on to develop a chronic form of the disease, which may involve heart valve infection (endocarditis) and other serious complications.

In chronic cases, symptoms may include night sweats, weight loss, fatigue, shortness of breath, or swelling of limbs due to heart involvement. 

Treatment

Most people with mild or asymptomatic infection recover without antibiotic treatment.

For symptomatic acute Q fever, the first-line antibiotic recommended is Doxycycline (e.g., adult: 100 mg twice daily for 14 days) when diagnosis is suspected.

Treatment should begin as soon as Q fever is suspected (even if lab results pending) for best outcomes.

For chronic Q fever (especially endocarditis or vascular infection), long-term antibiotic combination therapy is used (e.g., doxycycline + Hydroxychloroquine) for many months (sometimes ≥ 18 months). 

There is currently no vaccine for Q fever available for use in the United States.