title: An outbreak of chikungunya in southern Thailand from 2008 to 2009 caused by African strains with A226V mutation.
abstract: OBJECTIVE
  To elucidate clinical and molecular characteristics of chikungunya fever (CHIK fever) from the 2008-2009 outbreak caused by chikungunya virus (CHIKV) in southern Thailand.
  
  
  METHODS
  Three hundred and eighty-one sera from 332 patients with acute febrile illness were tested for anti-CHIKV IgM antibody by ELISA. A molecular analysis of these sera was performed using a semi-nested reverse transcriptase polymerase chain reaction (RT-PCR), followed by direct sequencing and phylogenetic analysis.
  
  
  RESULTS
  One hundred and seventy-nine patients were diagnosed with CHIK fever by molecular analysis and/or anti-CHIKV IgM antibody detection. Patients diagnosed with CHIK fever were significantly older than controls (mean age 38.8±19 vs. 28.7±18 years, p<0.0001) and presented with arthralgia more often than controls. One hundred percent of the sera were positive by RT-PCR, whereas only 10% were positive in serological tests for anti-CHIKV IgM antibody by ELISA if the serum was obtained during the first 4 days of fever. In contrast, CHIKV-specific IgM antibody by ELISA was found in 100% of patients, whereas 15% of patients were positive by RT-PCR if the serum was obtained more than 9 days after the onset of fever. RT-PCR for CHIKV should be performed if the patients present within the first 4 days of fever. Patients presenting after at least 9 days of fever should be tested for IgM antibody. Based on phylogenetic analysis, the CHIKV strains isolated belong to African genotypes harboring the E1 A226V mutation, indicating a single origin of the 2004-2009 CHIKV outbreaks.
  
  
  CONCLUSIONS
  The novel CHIKV mutation could potentially modify the epidemiological presentation of CHIK fever. Early diagnosis of CHIK fever is essential for preventing further massive outbreaks.
authors.affiliation: Center of Excellence in Clinical Virology, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Pornpimol
authors.initials: P
authors.lastname: Rianthavorn
authors.forename: Kesmanee
authors.initials: K
authors.lastname: Prianantathavorn
authors.forename: Norra
authors.initials: N
authors.lastname: Wuttirattanakowit
authors.forename: Apiradee
authors.initials: A
authors.lastname: Theamboonlers
authors.forename: Yong
authors.initials: Y
authors.lastname: Poovorawan
mesh_terms: D000293:Adolescent; D000328:Adult; D000349:Africa; D018354:Alphavirus Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology / Q000821:virology*; D019943:Amino Acid Substitution; D000914:Antibodies, Viral / Q000097:blood; D001483:Base Sequence; D016022:Case-Control Studies; D002646:Chikungunya virus / Q000145:classification / Q000235:genetics* / Q000276:immunology; D002648:Child; D004279:DNA, Viral / Q000235:genetics; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D013785:Thailand / Q000453:epidemiology; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D004279:DNA, Viral; D007075:Immunoglobulin M