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Disease overviewWorldwide

What is babesiosis?

Babesiosis is caused by microscopic Babesia parasites that infect red blood cells. It is commonly transmitted by certain infected ticks, although other rare transmission routes exist.

Reviewed by VuxLore® Knowledge Team For Everyone

Short answer

Babesiosis is caused by microscopic Babesia parasites that infect red blood cells. It is commonly transmitted by certain infected ticks, although other rare transmission routes exist.

At a glance

Some infections cause no symptoms, while others can cause a malaria-like illness and become severe in higher-risk people.

Key takeaways

• Babesiosis is parasitic, not bacterial.

• Symptoms may take weeks or longer to appear.

• People without a spleen or with weakened immunity can face greater risk.

An infection of red blood cells

Symptoms can include fever, chills, sweats, headache, body aches, nausea or fatigue. Destruction of red blood cells can cause haemolytic anaemia.

Risk is not equal for everyone

Older adults, people without a spleen and those with weakened immune systems may develop severe disease. Geographic distribution and the Babesia species involved vary internationally.

Sources and further reading

US Centers for Disease Control and Prevention: About Babesiosis

US Centers for Disease Control and Prevention: Tickborne Diseases of the United States

European Centre for Disease Prevention and Control: Tick-borne diseases