What Duffy-negative means for malaria

The Duffy blood group is based on a marker found on the surface of red blood cells. Some malaria parasites use this marker to enter red blood cells. When the marker is absent, infection with Plasmodium vivax may be less likely, particularly in people whose blood cells are Duffy-negative.

This is a difference in susceptibility, not immunity. Plasmodium falciparum, the malaria parasite responsible for many severe infections, does not depend on the Duffy marker in the same way. Other malaria parasites may also cause illness. A Duffy-negative result therefore cannot explain away fever after time in a malaria-risk area.

Duffy status is usually identified through blood group testing or specialised laboratory testing. It is not a malaria test, and it cannot show whether parasites are currently present in your blood.

Before travel, arrange a travel-health consultation if you may visit a malaria-risk region. A clinician can review the itinerary, season, accommodation and your health history, then discuss mosquito-bite prevention and malaria prophylaxis when appropriate.

After returning, seek medical advice promptly for fever, chills, headache, sweating, unusual tiredness or muscle aches if you have recently been in a malaria-risk area. Tell the clinician where you travelled and when, even if the trip was weeks or months ago. Ask whether a blood test for malaria is needed; a Duffy-negative result should not be used as a substitute for that assessment.

Take prescribed preventive medicine exactly as directed, use insect repellent and wear clothing that limits exposed skin. No preventive measure removes the need to assess a compatible illness.

Get urgent medical care for fever or feeling acutely unwell after travel to a malaria-risk area, especially with confusion, fainting, trouble breathing, repeated vomiting, severe weakness, yellowing of the skin or eyes, or a seizure. Malaria can worsen quickly, and early symptoms may resemble a routine viral illness.

Do not wait for symptoms to follow a predictable pattern, and do not delay care because you are Duffy-negative or because you took preventive medicine. If severe symptoms are present, tell emergency staff about the travel history and any malaria medication taken.

You could ask: Does my Duffy status change my malaria risk for this destination? Which preventive measures fit my itinerary? What symptoms should prompt testing after I return? If my first test is negative but fever continues, when should I be reassessed?