persons identified for this cohort were recruited in a passive febrile surveillance study in 15 health centers in 4 peruvian cities : iquitos , yurimaguas , chanchamayo , and puerto maldonado ( figure 1 ) . persons meeting the following criteria were recruited : age > 5 years , oral / tympanic temperature > 38c ( or axillary > 37.5c ) , and no obvious focus of infection . written consent was obtained from all adults and from a parent or guardian for participants < 18 years of age ; participants 817 years of age also provided written assent . sites for study of mayaro virus  infected patients are marked with a dot . compared with the day of the visit for acute illness ( acute - phase visit ) , follow - up evaluations occurred at 20 ( sd ) days ( 10 days ) , 3 months ( 10 days ) , 6 months ( 15 days ) , and 12 months ( 30 days ) . at the acute - phase visit and at all follow - up visits , a blood sample was obtained . for every participant , we attempted to determine the cause of infection by testing acute - phase serum for virus in ae . albopictus ( c6/36 ) and african green monkey kidney ( vero 76 ) cell culture ( with immunofluorescence assay ) and for viral nucleic acid by reverse transcription pcr ( rt - pcr ) . capture igm and igg elisas were performed at 1:100 dilution on the acute - phase and all follow - up samples to evaluate antibody responses to mayv and other endemic arboviruses ( i.e. , venezuelan equine encephalitis , oropouche , group c , guaroa , and dengue viruses ) ( 6 ) . samples with detectable igm or igg were serially diluted and retested . seroconversion was defined as a > 4-fold increase in igm titer between the acute - phase visit and the second visit . a mayaro fever case was defined as igm seroconversion or virus detected by isolation or by rt - pcr . in addition , we collected throat swabs from participants with pharyngeal erythema at the acute - phase visit and urine samples from the 3-month follow - up visit to determine the presence of mayv with rt - pcr ( 13 ) . of 2,094 febrile participants enrolled , 16 ( 0.8% ) had mayaro fever ( table 1 ) . of the 16 persons with mayaro fever , 11 had mayv isolated by the cell culture assays ( 11 in both vero 76 and c6/36 ) , 13 were mayv positive by rt - pcr , and all had igm elisa seroconversion between the acute - phase and 20-day follow - up visits ( table 1 ) . in all 16 participants , no igm elisa seroconversion occurred for endemic non - alphavirus viruses ( i.e. , oropouche , group c , guaroa , and dengue viruses ) . four participants demonstrated igm elisa seroconversion against another alphavirus , venezuelan equine encephalitis virus , but these 4 all had mayv identified by immunofluorescence assay and by rt - pcr . using rt - pcr , we did not detect mayv in 2 acute visit throat swabs , any second - visit ( 20-day ) serum samples , and any third - visit ( 3-month ) urine samples . * mayv , mayaro virus ; rt - pcr , reverse transcription pcr ; neg , negative ;  , visits not attended by the patient . isolation and rt - pcr results are from the acute - phase visit .  for elisa igm and igg results , endpoint titration values were determined . besides fever , the most common symptoms affecting participants in the acute stage of mayv infection were malaise , headache , arthralgia , myalgia , and retro - orbital pain . the prevalence of these and other nonjoint signs and symptoms at the acute - phase and follow - up visits are available in the technical appendix table . although reports of joint pain waned in study participants by the second ( 20-day ) visit , complaints increased at 3 months and persisted in 54% even after 12 months . joints of the hand , wrist , elbow , feet , and knee were identified as problematic , whereas hip or axial joint pain was rare ( figure 2 ) . the chronic joint pain often interfered with activities of daily living ( table 2 ) . prevalence of joint involvement at the different follow - up visits for mayaro virus infection , amazon basin region , peru , 20102013 . denominators varied because of varying numbers of participants reporting to each follow - up visit . m03 , 3-month follow - up ; m06 , 6-month follow - up ; m12 , 12-month follow - up . this study demonstrated that persons with acute mayaro fever often have many nonspecific symptoms but may continue to have chronic joint pain for at least 1 year after acute illness . it also indicates the need to consider mayv infection in patients with seronegative arthritis ( i.e. , negative rheumatoid factor and antinuclear antibodies ) in regions to which mayv is endemic . previous reports have documented persistent joint pain after mayv infection ( 25,9,11 ) , although all of these were either solitary case reports or case series of < 4 persons . by using follow - up periods ranging from 1 month to 12 months , most of these studies identified persistent symptoms in the fingers . involvement of joints of the wrist , ankle , and knee also were mentioned , similar to the participants in our study . long - term manifestations of infection with other alphaviruses have been more robustly characterized , with persistent arthralgia being commonly described . follow - up of chikungunya virus  infected patients on runion island revealed that 60% had joint pain > 3 years after acute illness that most often affected the fingers , wrists , knees , and ankles ( 14 ) . sindbis virus infection in a cohort in finland resulted in persistent arthralgia lasting at least a year in half of those infected , with ankles , fingers , and wrists being most often affected ( 15 ) . one caveat of our study and other studies is the difficulty in definitively attributing persistent arthralgia solely to viral infection , although our participants limitations in activities of daily living were all described as starting after their acute mayaro fever illness . igm seroconversion occurred in all of the participants in our study that were identified with either isolation or rt - pcr , consistent with another report that noted the reliability of serology in detecting mayv infection ( 9 ) . in our study participants identified by serology , both rt - pcr and culture were more sensitive than what others have found for sindbis virus infection , for which 1 study found sensitivities of 7% and 1% , respectively ( 15 ) . however , rt - pcr and culture were negative in the only 2 participants in our study who had mayaro fever after day 3 of symptoms , suggesting a narrow window when these assays may be effective . no effective vaccine or antiviral agent exists for the arthritogenic alphaviruses , and treatment relies mainly on supportive modalities , such as nonsteroidal anti - inflammatory medications ( 12 ) . our results offer evidence that mayv , similar to other alphaviruses , may cause protracted joint symptoms and provide further impetus to the development of more effective preventive and treatment strategies . signs and symptoms in patients with mayaro virus infection at the acute - phase visit and each follow - up visit , amazon basin region , peru , 20102013 .
during 20102013 , we recruited 16 persons with confirmed mayaro virus infection in the peruvian amazon to prospectively follow clinical symptoms and serologic response over a 12-month period . 
 mayaro virus infection caused long - term arthralgia in more than half , similar to reports of other arthritogenic alphaviruses .