An Outbreak of Japanese Encephalitis among Lao People from Xaignabouli, Laos at Nan Hospital, June - July 2014

Abstract

Background: On 12 July 2014, Bureau of Epidemiology received a notification of cluster of encephalitis among Lao people referred to get treatment at 3 hospitals in Nan Province. Four cases were identified and one was died. The surveillance and rapid response teams from national, regional and local levels conducted an outbreak investigation at Nan Province during 14 – 15 July 2014. The objectives were to confirm diagnosis and existence of outbreak, to describe the epidemiological characteristics and to recommend the prevention and control measure.
Methods: Descriptive epidemiology was conducted and medical records of the patients at all three hospitals (i.e., Chaloem Pra Kiat, Pua Crown Prince and Nan) were reviewed. We interviewed attending clinician and case’s relatives and collected samples of blood and cerebrospinal fluid to test for etiology. Active case finding among Lao people was done in the hospitals during May – July 2014.
Results: Four (2 males and 2 females) cases of encephalitis in Lao cases were detected. One case died and three recovered with neurological complication. All cases lived in Xaignabouli Province, Lao PDR. The first case was 16-yearsold male adolescent and lived in Hongsa District. His onset was on 20 June 2014. He was referred from Xaignabouli Hospital and treated at Nan Hospital. CT brain revealed enhancing lesions at thalamus and midbrain. He survived following the treatment. The second case was 17-years-old male adolescent and lived in Xianghon District. His onset was on 30 June 2014. He was referred from Xianghon Hospital and treated at Nan Hospital. CT brain showed abnormality at thalamus. He was expired on 4 July 2014. The third case was 18-years-old female adolescent and her onset was on 4 July 2014. She lived near first case’s habitat around 4 km far away. Her CT brain revealed leptomeningeal enhancement. She was recovered. The last case was 11-month-old female infant and lived in Xianghon District. Her onset was on 15 July 2014. She was recovered. All cases were confirmed positive for JEV IgM in CSF and 3 cases were additionally positive for JEV IgM in their blood samples. Furthermore, there were also negative PCR of Herpes Simplex and pan-enterovirus in CSF. There were no additional cases among Thai and Loa people who sought care at those three hospitals between May and July 2014.
Discussions and Conclusion: Four cases of lab-confirmed Japanese Encephalitis among Lao people during June – July 2014, rainy season with abundance of mosquitoes. Most of the cases were adolescent but one was infantile. This reflects possible circulation of JE virus in the communities. There will be more people infected without symptom since the ratio of symptomatic and asymptomatic is 1 : 300. We recommended Nan Provincial Health Offices to provide catch-up JEV vaccination, especially in Thai-Lao border area. Lao PDR implemented mass JEV vaccination for their 1.5 million population of children nationwide on 1st April 2015 by GAVI support.