Chikungunya fever in travelers returning to Europe from the Indian Ocean region, 2006

Abstract

Chikungunya fever has spread through several Indian Ocean islands and India, including popular travel destinations. To compare usefulness of diagnostic tests and to understand reasons for the magnitude and severity of an outbreak, we used 3 diagnostic methods to test 720 samples from 680 patients returning to Europe from the Indian Ocean region in 2006. Chikungunya infection was confirmed for 24.4% patients in the first half of the year and for 9.9% in the second half. Reverse transcription-PCR was positive for all samples taken up to day 4 after symptom onset. Immunofluorescence detected immunoglobulin (Ig) M on day 1 and IgG on day 2 for some patients, and in all patients from day 5 onward. Soon after onset of symptoms, patients had IgG and IgM and high viral loads (some >10(9) copies/mL plasma). These data will help healthcare providers select diagnostic tests for returning travelers.

Figure 1

Immunoglobulin (Ig) M and IgG titers in 153 samples from 121 patients. Some patients are represented more than once if multiple specimens were submitted for testing. CHIKV, chikungunya virus.

Figure 2

A) Rates of positive results from assays for immunoglobulin (Ig) M, IgG, and virus RNA, first 10 days of symptoms. Numbers above bars are numbers of samples (and patients). B) Left panel, viral loads in serum or plasma in antibody-negative, PCR-positive patients (n = 21, left column) and in antibody-positive, PCR-positive patients (n = 6, right column). All patients were sampled during first 3 days of symptoms. Right panel, viral loads in all antibody-negative, PCR-positive samples. Error bars represent interquartile ranges. C) Viral loads, antibodies, and virus isolation from 47 samples positive by reverse transcription–PCR (RT-PCR). Virus isolation + indicates isolation success as confirmed by cytopathogenic effect and direct immunofluorescence assay. Antibody detection + indicates an IgG or IgM titer >10 by immunofluorescence assay.

Figure 3

Viral loads for all PCR-positive samples (left panel) and immunoglobulin (Ig)–negative/PCR-positive samples (right panel), depending on types of mutation (alanine or valine at amino acid position 226 of the envelope 1 protein, as shown on the x-axis). Boxes represent the innermost 2 quartiles of data; horizontal line shows the mean; whiskers represent the outermost 2 quartiles.