High prevalence of mumps in Lao People's Democratic Republic.

In the Lao People's Democratic Republic (PDR), mumps is not a notifiable disease and mumps vaccine is currently not included in the routine childhood immunization programme. In order to assess the burden of disease, we investigated the seroprevalence of mumps-specific IgG antibodies across four provinces. In addition, we genetically characterized mumps viruses from the past 3 years from several outbreaks and single cases. Blood and/or throat swabs from suspected cases were investigated for specific IgM antibodies or viral RNA. Mumps cases occurred between March and November in 2011-2013 and 5- to 15-year-olds were most affected. Four sequences from an outbreak in the north of Lao PDR in 2011 were identical and belonged to genotype G. Eight sequences from two outbreaks and two individual cases from 2012 and 2013 belonged to genotype J. In addition, sera collected from 2379 healthy infants and school pupils aged between 9 months and 19 years and from pregnant women aged between 16 and 46 years were investigated for mumps-specific IgG. Overall, 58.2% were positive, 39.5% were negative and the remaining 2.3% were equivocal. The seropositivity increased with age, with the lowest percentage found in <1-year-old infants (9.1%) and the highest in the cohort of pregnant women (69.2%). More female subjects than male subjects were seropositive (60.4 vs. 54.9%). There were some differences between the locations. Mumps should be a notifiable disease in Lao PDR in order to get more accurate case numbers and cost estimates for public health-care, and vaccination of children and high-risk groups should be considered.

Measles epidemiology and outbreak investigation using IgM test in Laos.

Following the Pan American Health Organization (PAHO) recommendation on measles elimination, the Western Pacific Region of WHO (WPR) is emphasizing accelerated measles control programme especially since the achievement of polio eradication in WPR in 2000. This includes upgraded surveillance and mass measles vaccination campaign for children aged 9 months to 4 years. However, there are limited scientific evidences supporting the feasibility of this programme in Laos. To examine measles elimination feasibility in the country, we conducted measles outbreak investigation using immunoglobulin M (IgM). From March 1999 to March 2000, we conducted 7 outbreak investigations. At the outbreak sites, we examined clinical manifestations of cases and collected individual data. About five blood samples were drawn from each outbreak, and IgM antibodies to measles were tested. Of 7 investigated outbreaks, 5 were confirmed as measles, one was chickenpox, and one occurred in the inaccessible area due to flooding. In a village of high land Lao, blood drawn was refused. Of 185 cases, 64 (34.6%) cases were immunized, and 110 (59.5%) were unimunized. The estimated vaccine efficacy is 67.9%. The number of measles cases among school-aged children was 74 (40.0%), which represented 2.5% of the total population in investigated villages. Our findings showed various difficulties of the surveillance and the limited outcomes of mass measles vaccination campaign under the accelerated measles control programme by WPR. Efforts to improve cold chain as well as increasing routine immunization coverage must be the priority of measles control.

Risk of poliomyelitis importation and re-emergence in Laos.

The declaration of poliomyelitis eradication in the western pacific region is scheduled for Oct 29, 2000, in Kyoto, Japan. Our survey in the border areas of the southeast Asia region, however, revealed that there remains a risk of re-emergence and importation of poliomyelitis into Laos. We report the evidence based on our border area investigations during the past 4 years under the bilateral supervision of the governments of Laos and Japan.

Polio surveillance in Lao PDR: a two-year experience of active case search, 1994-96.

The underdeveloped health infrastructure and limited epidemiological data on polio are major obstacles to the establishment of the acute flaccid paralysis (AFP) surveillance system in Lao People's Democratic Republic (Lao PDR). We initiated a nationwide active case search for case investigations at the community level in March 1994 to support the development of the AFP surveillance system. We identified 164 polio cases that occurred between 1979 and 1993 in 511 villages, indicating that wild poliovirus had circulated extensively during that period. Of these, only 59 (36 per cent) had visited health facilities, and polio was diagnosed in 15 (9 per cent). As national immunization days (NIDs) progressed, the number of polio cases decreased to an undetectable level after 1994. The active case search was useful for educating the local staff about AFP and the components of a surveillance system, and as an adjunct to national AFP surveillance programme in the country as it approaches the goal of polio eradication.