Mayaro fever in Germany

Acknowledgement
BEACON thanks Dr. Astrid Niederfahrenhorst, MD (Specialist for Infectious Diseases and Tropical Medicine, Institute of Infectious Diseases and Tropical Medicine at the Ludwig Maximilians University Hospital, Munich, Germany; GeoSentinel Network) for the submission of this report.

Key findings
An adult German traveler was confirmed to have Mayaro virus (MAYV) infection after returning from South America, especially following a visit to Peru, emphasizing the potential risk of imported cases from these endemic regions.

Case description

• The patient traveled to Peru, Costa Rica, Colombia, and Panama between the end of 2024 and mid-June 2025. During their trip, the patient took a several-day jungle trek in the north-central part of Peru and developed a patchy, very itchy rash on the trunk, swollen feet, and fatigue. The temperature was not measured, and the symptoms resolved after a few days.
• One week later, the patient developed joint pains, especially in the ankles, and later also in the finger joints and wrists, along with some back pain. The joint pains persisted until the patient sought medical care in the first week of July 2025.

Laboratory results

• Liver, kidney function tests, and blood counts were normal, as was lactate dehydrogenase. C-reactive protein and erythrocyte sedimentation rate (ESR) were slightly elevated.
• Mayaro serologies: highly positive IgM (1:320, normal range <1:20) and IgG (1:20 480, normal range <1:20), consistent with a Mayaro virus infection within the previous three months.
• Chikungunya serologies: moderately positive IgG ELISA (Ratio 2.23, normal range <0.8) with negative IgM.
• Serologies were performed via the indirect immunofluorescence test.
• PCR testing was not performed as the patient was presenting two months after illness. 

Epidemiological analysis

• This is very likely a case of Mayaro fever, with serologies strongly indicating MAYV compared to chikungunya virus. An earlier positive PCR during illness is often confirmatory. The case highlights the importance of considering Mayaro fever in the clinical suspicion for travelers with suggestive symptomatology returning from endemic areas to non-endemic regions.
• The Mayaro virus, an emerging alphavirus, has historically affected regions in South and Central America, with seasonal patterns linked to increased mosquito activity. The virus causes occasional outbreaks in South America, especially in communities near forested areas. Its primary vector is the Haemagogus janthinomys mosquito, but laboratory research shows that other species, including Aedes aegypti, Ae. albopictus, and certain Anopheles mosquitoes can also transmit the virus.
• Concerns about the global spread of MAYV are increasing as infections have recently been found in travelers returning to Europe and North America from areas where the virus is endemic.
• Reports of Mayaro virus cases in returning travelers still remain rare. A databank survey mentioned in a 2024 report identified a total of 10 imported cases in European travelers. However, it is widely believed that the actual number of cases is probably higher due to underdiagnosis and misdiagnosis, as the symptoms of Mayaro fever can be similar to other arboviral infections like dengue and chikungunya.
• A notable recent event involved a cluster of four Mayaro virus infections in a German film crew returning from Suriname in February 2024. This case series highlights the potential for clusters of infections in travelers.