title: Hidden varicella outbreak, Luang Prabang Province, the Lao People's Democratic Republic, December 2014 to January 2015.
abstract: BACKGROUND
  In January 2015, the Lao People's Democratic Republic Ministry of Health received a report of 34 cases of fever and rash with one laboratory-confirmed measles case in Houitone village, Pakseng District of Luang Prabang Province. Between 21 and 27 January, we conducted a field investigation to determine the etiology, magnitude and severity of this outbreak.
  
  
  METHODS
  We conducted active case findings in Houitone and neighbouring villages and collected information on age, location, date of rash onset, symptoms and measles vaccination status. We collected serum samples from cases with rash onset of less than 28 days and tested for measles and rubella IgM using enzyme-linked immunosorbent assay.
  
  
  RESULTS
  Between 22 December 2014 and 23 January 2015, 190 fever and rash cases were identified in seven villages in Pakseng District with the majority of the cases in Houitone village. The most affected age group was between 1 and 9 years. The majority of the rashes were vesicular. Of the additional 43 serum samples collected, no samples tested positive for measles or rubella IgM. The clinical manifestation and epidemiology of the disease suggested a varicella outbreak.
  
  
  CONCLUSIONS
  The rapid response to a single laboratory-confirmed measles case did not identify a measles outbreak but suggested a varicella outbreak. Low measles vaccination coverage led us to recommend a routine catch-up vaccination campaign. We also recommend collecting information of rash types and photos of rashes in future fever and rash outbreaks to better differentiate potential etiologies.
authors.affiliation: National Center for Laboratory and Epidemiology, Ministry of Health, Vientiane Capital, the Lao People's Democratic Republic.
authors.forename: Bounthanom
authors.initials: B
authors.lastname: Sengkeopraseuth
authors.affiliation: Office of the WHO Representative in the Lao People's Democratic Republic, Vientiane Capital, the Lao People's Democratic Republic.
authors.forename: Khonesavanh
authors.initials: K
authors.lastname: Bounma
authors.affiliation: National Center for Laboratory and Epidemiology, Ministry of Health, Vientiane Capital, the Lao People's Democratic Republic.
authors.forename: Chansone
authors.initials: C
authors.lastname: Siamong
authors.affiliation: Office of the WHO Representative in the Lao People's Democratic Republic, Vientiane Capital, the Lao People's Democratic Republic.
authors.forename: Siddhartha
authors.initials: S
authors.lastname: Datta
authors.affiliation: National Center for Laboratory and Epidemiology, Ministry of Health, Vientiane Capital, the Lao People's Democratic Republic.
authors.forename: Bouaphanh
authors.initials: B
authors.lastname: Khamphaphongphane
authors.affiliation: National Center for Laboratory and Epidemiology, Ministry of Health, Vientiane Capital, the Lao People's Democratic Republic.
authors.forename: Phengta
authors.initials: P
authors.lastname: Vongphachanh
authors.affiliation: Office of the WHO Representative in the Lao People's Democratic Republic, Vientiane Capital, the Lao People's Democratic Republic.
authors.forename: Dapeng
authors.initials: D
authors.lastname: Luo
authors.affiliation: Emerging Disease Surveillance and Response Unit, Division of Health Security and Emergencies, World Health Organization Regional Office for the Western Pacific, Manila, Philippines .
authors.forename: Michael
authors.initials: M
authors.lastname: O'Reilly
authors.affiliation: Office of the WHO Representative in the Lao People's Democratic Republic, Vientiane Capital, the Lao People's Democratic Republic.
authors.forename: Cindy H
authors.initials: CH
authors.lastname: Chiu
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007812:Laos / Q000453:epidemiology; D008297:Male; D008457:Measles / Q000175:diagnosis / Q000453:epidemiology*; D012409:Rubella / Q000175:diagnosis / Q000453:epidemiology; D011795:Surveys and Questionnaires