Safety and Efficacy of Lemborexant in Patients With Irregular Sleep-Wake Rhythm Disorder and Alzheimer's Disease Dementia: Results From a Phase 2 Randomized Clinical Trial

BACKGROUND

Irregular sleep-wake rhythm disorder (ISWRD) is a common sleep disorder in individuals with Alzheimer's disease dementia (AD-D).

OBJECTIVES

This exploratory phase 2 proof-of-concept and dose-finding clinical trial evaluated the effects of lemborexant compared with placebo on circadian rhythm parameters, nighttime sleep, daytime wakefulness and other clinical measures of ISWRD in individuals with ISWRD and mild to moderate AD-D.

DESIGN

Multicenter, randomized, double-blind, placebo-controlled, parallel-group study.

SETTING

Sites in the United States, Japan and the United Kingdom.

PARTICIPANTS

Men and women 60 to 90 years of age with documentation of diagnosis with AD-D and Mini-Mental State Exam (MMSE) score 10 to 26.

INTERVENTION

Subjects were randomized to placebo or one of four lemborexant treatment arms (2.5 mg, 5 mg, 10 mg or 15 mg) once nightly at bedtime for 4 weeks.

MEASUREMENTS

An actigraph was used to collect subject rest-activity data, which were used to calculate sleep-related, wake-related and circadian rhythm-related parameters. These parameters included least active 5 hours (L5), relative amplitude of the rest-activity rhythm (RA) and mean duration of sleep bouts (MDSB) during the daytime. The MMSE and the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog) were used to assess for changes in cognitive function.

RESULTS

Sixty-two subjects were randomized and provided data for circadian, daytime and nighttime parameters (placebo, n = 12; lemborexant 2.5 mg [LEM2.5], n = 12; lemborexant 5 mg [LEM5], n = 13, lemborexant 10 mg [LEM10], n = 13 and lemborexant 15 mg [LEM15], n = 12). Mean L5 showed a decrease from baseline to week 4 for LEM2.5, LEM5 and LEM15 that was significantly greater than with placebo (all p < 0.05), suggesting a reduction in restlessness. For RA, LS mean change from baseline to week 4 versus placebo indicated greater distinction between night and day with all dose levels of lemborexant, with significant improvements seen with LEM5 and LEM15 compared with placebo (both p < 0.05). The median percentage change from baseline to week 4 in MDSB during the daytime indicated a numerical decrease in duration for LEM5, LEM10 and LEM15, which was significantly different from placebo for LEM5 and LEM15 (p < 0.01 and p = 0.002, respectively). There were no serious treatment-emergent adverse events or worsening of cognitive function, as assessed by the MMSE and ADAS-Cog. Lemborexant was well tolerated. No subjects discontinued treatment.

CONCLUSIONS

This study provides preliminary evidence of the potential utility of lemborexant as a treatment to address both nighttime and daytime symptoms in patients with ISWRD and AD-D.

Treatment outcome of tuberculosis patients detected using accelerated vs. passive case finding in Myanmar

SETTING

Several projects involving accelerated or active case finding (ACF) of tuberculosis (TB) cases are being implemented in Myanmar. However, there is a concern that patients detected using ACF have poorer TB treatment outcomes than those detected using passive case finding (PCF).

OBJECTIVE

To assess differences in the demographics, clinical profile and treatment outcomes of patients detected using ACF and PCF.

DESIGN

Retrospective cohort study of TB patients diagnosed and enrolled for treatment during 2014-2016.

RESULTS

Of 16 048 patients enrolled, 2226 (16%) were detected using ACF; the treatment success rate (cured and completed) was 88%. A higher proportion of cases detected using ACF were aged 55 years, human immunodeficiency virus (HIV) negative and sputum smear-positive pulmonary TB. After adjusting for differences in demographic and clinical characteristics, we found that treatment outcomes in patients detected using ACF and PCF were not significantly different (adjusted relative risk [aRR] 0.89, 95%CI 0.78-1.00). Male sex, age  55 years, patients with a previous history of TB and HIV positivity were independently associated with unsuccessful outcomes.

CONCLUSION

ACF detected a significant proportion of TB cases in study townships; treatment outcomes in cases detected using ACF and those detected using PCF were similar. More tailored interventions are needed to improve treatment outcomes in patients at a higher risk of unsuccessful treatment outcomes.

Cost-effectiveness of a new strategy to detect pulmonary tuberculosis in household contacts in Myanmar

SETTING

Guidelines regarding household contact tracing for pulmonary tuberculosis (TB) in different countries vary according to case detection methods.

OBJECTIVE

To compare costs spent on detecting one TB case among household contacts between different contact tracing strategies in Mandalay City, Myanmar.

METHODS

Cost estimation of case detection and diagnostic procedures using two different strategies were calculated. A modified conventional model included screening for TB signs and symptoms, sputum examination for those with positive signs and symptoms and chest X-ray (CXR) for those with negative sputum results. An interventional model included CXR, sputum examination if CXR was abnormal and Xpert® MTB/RIF assay for those with negative sputum results. Estimated costs in each model were stratified by age <15 and 15 years.

RESULTS

The additional cost per TB case detected using the interventional model was US$35.41 compared to the modified conventional model. The probability that the interventional model was cost-effective using a threshold of US$100 per case detected was 81% (83% for those aged 15 years and 65% for those aged <15 years).

CONCLUSIONS

The interventional model was more cost-effective in detecting one more pulmonary TB case among household contacts than the modified conventional model.

Homer is concentrated at the postsynaptic density and does not redistribute after acute synaptic stimulation

Homer is a postsynaptic density (PSD) scaffold protein that is involved in synaptic plasticity, calcium signaling and neurological disorders. Here, we use pre-embedding immunogold electron microscopy to illustrate the differential localization of three Homer gene products (Homer 1, 2, and 3) in different regions of the mouse brain. In cross-sectioned PSDs, Homer occupies a layer ∼30-100nm from the postsynaptic membrane lying just beyond the dense material that defines the PSD core (∼30-nm-thick). Homer is evenly distributed within the PSD area along the lateral axis, but not at the peri-PSD locations within 60nm from the edge of the PSD, where type I-metabotropic glutamate receptors (mGluR1 and 5) are concentrated. This distribution of Homer matches that of Shank, another major PSD scaffold protein, but differs from those of other two major binding partners of Homer, type I mGluR and IP3 receptors. Many PSD proteins rapidly redistribute upon acute (2min) stimulation. To determine whether Homer distribution is affected by acute stimulation, we examined its distribution in dissociated hippocampal cultures under different conditions. Both the pattern and density of label for Homer 1, the isoform that is ubiquitous in hippocampus, remained unchanged under high K(+) depolarization (90mM for 2-5min), N-methyl-d-asparic acid (NMDA) treatment (50μM for 2min), and calcium-free conditions (EGTA at 1mM for 2min). In contrast, Shank and calcium/calmodulin-dependent kinase II (CaMKII) accumulate at the PSD upon NMDA treatment, and CaMKII is excluded from the PSD complex under low calcium conditions.

Automated genotyping for accurate assignment of the (AT)xNz(AT)y motif within the beta-globin locus control region-hypersensitive site 2

Within the core region of hypersensitive site 2 of the beta-globin locus control region is the (AT)xNz(AT)y motif, which comprises two short tandem repeats of dinucleotide (AT) interrupted by a short variable DNA sequence (Nz). The motif is usually investigated using direct sequence analysis of specifically amplified DNA, but without family studies, phase alignment of the two tandem repeats, occasionally confounded by a variable N sequence in between, can be erroneous. We combined the technique of automated genotyping with direct sequence analysis to demonstrate that it is possible to overcome this problem; the approach should be applicable for the investigation of other sequence repeats of this nature.

Effect of encapsulation on absorption of sumatriptan tablets: data from healthy volunteers and patients during a migraine

BACKGROUND

Some comparative trials of selective serotonin 1B/ID-agonists in migraine have reported -15% lower efficacy for sumatriptan tablets than that reported in placebo-controlled trials.

OBJECTIVE

This study was designed to test the hypothesis that the encapsulation methods used to mask active drug may delay absorption of sumatriptan from dosing to 2 hours after dosing (the traditional end point in clinical trials of migraine treatment), an effect that may be enhanced by migraine-associated gastric stasis.

METHODS

Two randomized, open-label, 2-way crossover trials were conducted to evaluate the absorption and bioequivalence of conventional 50-mg sumatriptan tablets and encapsulated 50-mg sumatriptan tablets in supine, fasted, healthy volunteers (Glaxo Wellcome protocol SUM40270) and supine patients experiencing a migraine (Glaxo Wellcome protocol SUM40268). Absorption was assessed by calculating the area under the plasma concentration-time curve from dosing to 2 hours after dosing (AUC2) and the times to first measurable plasma concentration, 10 ng/mL, 20 ng/mL, and maximum plasma concentration. Data for the AUC from time zero to infinity and maximum plasma concentration were used to assess standard bioequivalence, which is considered to occur when the 90% CIs for the geometric mean treatment ratios (test/reference) fall between 0.8 and 1.25.

RESULTS

Study 1 included 26 healthy subjects (73% men, 27% women; mean age, 39.1 years), and study 2 included 30 patients with migraine (67% women, 33% men; mean age, 42.7 years). Sumatriptan absorption was delayed with the encapsulated tablet compared with the conventional tablet 0 to 2 hours after dosing, particularly during a migraine. AUC2 values with encapsulated sumatriptan compared with the conventional tablet were 21% lower in healthy volunteers (ratio of capsule/tablet, 0.79; 90% CI, 0.588-1.050) and 27% lower in patients experiencing a migraine (ratio of capsule/tablet, 0.73; 90% CI, 0.519-1.023). Standard bioequivalence was demonstrated in both healthy volunteers and patients experiencing a migraine.

CONCLUSIONS

Encapsulation delayed absorption of sumatriptan 0 to 2 hours after dosing, particularly during a migraine. This delay in absorption of the encapsulated form may account for the lower efficacy of sumatriptan in some comparative studies.

HIV transmission in sexual partners of persons with HIV/AIDS attending the Infectious Diseases Hospital, Yangon

A study was conducted in the Infectious Diseases Hospital, Yangon, for one year from August 1996 to 1997, to assess the extent and the factors related to HIV transmission among sexual partners of HIV/AIDS cases. It was a cross-sectional comparative study on 67 (61 males, 6 females) HIV positive individuals with or without AIDS, and their sexual partners. Separate interviews of index cases and partners were done, and clinical examination and laboratory tests for HIV and sexually transmitted diseases (STDs) were performed. HIV transmission was found in 41.8% of the partners. Male-to-female transmission was 39.3% (n=61) and female to male transmission was 66.7% (n=6), Seven and one half percent of the partners were suffering from AIDS. There were 4 (6.6%) pregnant mothers and 1 (25%) was HIV positive. Though 75% of the partners did not use condoms during their married life, HIV transmission was significantly reduced in the condom users (odds ratio (OR) = 0.18, 95% confidence interval (CI) 0.02-0.98 p = < 0.05). The seropositive men who were less than 30 years of age had greater HIV transmission (OR = 5.67, 95% CI 1.13-36.46). However, socio-demographic factors, number of marital partners and age of first sex partners, duration of marriage, number of sexual relationships between these couples, duration of HIV positivity and AIDS infection, immunological status of the index group and STD positivity among partners had no significant association with the transmission of HIV. This study demonstrated that the transmission of HIV was high among the sexual partners of persons with HIV infection. It also highlighted the requirement of effective counseling and preventive measures against HIV infection among the couples.

The effect of temperature and humidity on dengue virus propagation in Aedes aegypti mosquitos

The effect of temperature and relative humidity on dengue virus propagation in the mosquito as one of the possible contributing factors to dengue hemorrhagic fever (DHF) outbreaks was studied. Ae. aegypti mosquitos were reared under standard conditions and inoculated intrathoracically with dengue virus. Virus propagation in the mosquitos was determined at the temperature and relative humidity of all 3 seasons of Yangon and for the simulated temperature and relative humidity of Singapore. The virus propagation was detected by direct fluorescent antibody technique (DFAT) with mosquito head squash and the virus titer was determined by plaque forming unit test (PFUT) in baby hamster kidney-21 cells. The results show that the infected mosquitos kept under the conditions of the rainy season and under the simulated conditions of Singapore had a significantly higher virus titer (p=<0.05) when compared with the other 2 seasons of Yangon. So it is thought that the temperature and relative humidity of the rainy season of Yangon and that of Singapore favors dengue virus propagation in the mosquito and is one of the contributing factors to the occurence of DHF outbreaks.

Typing of urinary JC virus DNA offers a novel means of tracing human migrations

Although polyomavirus JC (JCV) is the proven pathogen of progressive multifocal leukoencephalopathy, the fatal demyelinating disease, this virus is ubiquitous as a usually harmless symbiote among human beings. JCV propagates in the adult kidney and excretes its progeny in urine, from which JCV DNA can readily be recovered. The main mode of transmission of JCV is from parents to children through long cohabitation. In this study, we collected a substantial number of urine samples from native inhabitants of 34 countries in Europe, Africa, and Asia. A 610-bp segment of JCV DNA was amplified from each urine sample, and its DNA sequence was determined. A worldwide phylogenetic tree subsequently constructed revealed the presence of nine subtypes including minor ones. Five subtypes (EU, Af2, B1, SC, and CY) occupied rather large territories that overlapped with each other at their boundaries. The entire Europe, northern Africa, and western Asia were the domain of EU, whereas the domain of Af2 included nearly all of Africa and southwestern Asia all the way to the northeastern edge of India. Partially overlapping domains in Asia were occupied by subtypes B1, SC, and CY. Of particular interest was the recovery of JCV subtypes in a pocket or pockets that were separated by great geographic distances from the main domains of those subtypes. Certain of these pockets can readily be explained by recent migrations of human populations carrying these subtypes. Overall, it appears that JCV genotyping promises to reveal previously unknown human migration routes: ancient as well as recent.

Risk factors in dengue shock syndrome

Despite a growing body of evidence predominantly, but not exclusively, from Thailand suggesting that the risk of developing dengue shock syndrome (DSS) is greatest following an anamnestic dengue infection, particularly if the most recent infection was with dengue 2 virus, there continues to be debate about the justification for these claims. This report describes a five-year, prospective study in two townships (suburbs) in Yangon (Rangoon) Myanmar (Burma) in which attempts were made to confirm the data from an earlier prospective study in Thailand and to address some of the criticism of earlier studies. This investigation found the incidence of anamnestic dengue infections in DSS patients to be significantly higher than in the community from which they were drawn and a significantly higher risk of developing DSS following an anamnestic infection (particularly with dengue 2 virus) than following a primary infection with any serotype.

Myelodysplastic syndrome with karyotype abnormality is associated with elevated F-cell production

A sensitive F-cell assay has been used to examine the production of fetal haemoglobin (Hb F) in a group of 77 adult patients with myelodysplastic syndrome (MDS), and a control group composed of 100 normal blood donors. Although the mean F-cell percentage in the MDS group (6.0%) is not statistically different from that in the normal blood donors (3.1%), a higher proportion of myelodysplastic patients have elevated F-cell values and the magnitude of the increases is greater than that observed in blood donors. In order to investigate the association further, the karyotypes of the MDS patients have been examined. 13/21 (61.9%) of the MDS patients with karyotypic abnormalities have F-cell values > 5%, compared to only 6/56 (10.9%) of the MDS patients with a normal karyotype and 11/100 (11%) of the blood donors. The observed difference in the distributions of F cells between the two subgroups of patients with MDS is highly significant (P < 0.0001).

Dissecting the loci controlling fetal haemoglobin production on chromosomes 11p and 6q by the regressive approach

The changes in the type of haemoglobin (Hb) produced during embryonic, fetal and adult life, have served as a paradigm for understanding the developmental regulation of human genes. A genetically determined persistence of fetal Hb synthesis has an ameliorating effect on beta thalassaemia and sickle cell anaemia, globally the commonest single gene disorders. The search for the putative gene(s) controlling the level of fetal Hb production has been extremely difficult because this trait may be influenced by several factors. We have studied a large kindred with hereditary persistence of fetal haemoglobin (HPFH). Using a genetic mapping strategy and statistical methods that account simultaneously for the effects of several genetic factors, we have demonstrated that in addition to the two factors (beta thalassaemia and Xmn I-G gamma site) on chromosome 11p, there is a third major genetic determinant for fetal Hb production localized on chromosome 6q.

Nonsense codon mutations in the terminal exon of the beta-globin gene are not associated with a reduction in beta-mRNA accumulation: a mechanism for the phenotype of dominant beta-thalassemia

We present in vivo evidence that there is no reduction in beta-mRNA accumulation in patients with nonsense codons in the terminal exon of the beta-globin gene. Using reverse transcriptase/polymerase chain reaction (RT-PCR), beta-globin cDNA was isolated from the reticulocytes of individuals heterozygous for nonsense codon mutations in exons II and III of the beta-globin gene. Clinically asymptomatic individuals heterozygous for mutations causing premature termination of translation in exon II [beta(0)39(C-T) and F/S71/72(+A)] were found to have almost no mutant beta-cDNA, whereas patients with nonsense codon mutations in exon III [beta 121(G-T) and beta 127(C-T)] with the clinical phenotype of thalassemia intermedia had comparable levels of mutant and normal beta-cDNA. Translation of the mutant beta-mRNA from patients with nonsense codon mutations in exon III would give rise to truncated beta-globin chains, which could explain the more severe phenotype seen in these individuals.

Changes in levels of anti-dengue virus IgG subclasses in patients with disease of varying severity

Extensive complement activation precedes onset of shock in dengue patients and complement "split products" C3a and C5a could be responsible, directly or indirectly, for the increased vascular permeability and disseminated intravascular coagulation which characterises dengue haemorrhagic fever (DHF) dengue shock syndrome (DSS). As IgG subclasses vary in their capacity to activate the classical complement pathway after combining with antigen, we have used an indirect enzyme linked immunosorbent assay (ELISA) to assess levels of IgG1-4 against each dengue serotype in acute and convalescent sera from patients with disease of varying severity. Acute phase sera from patients with dengue haemorrhagic fever (DHF) or dengue shock syndrome (DSS) contained higher levels of anti-dengue antibodies of the IgG1, complement fixing, subclass than similar sera from dengue fever (DF) patients. Conversely, acute phase sera from DHF and DSS patients contained lower levels of anti-dengue antibodies of the poor complement activating IgG2 subclass than acute phase sera from DF patients. No significant differences were detected between the levels of anti-dengue IgG3 and IgG4 antibody in acute phase sera from DF, DHF, and DSS patients. With the exception of levels of anti-dengue IgG2 antibody from DHF patients which were lower than those from DF and DSS patients, levels of anti-dengue IgG1, IgG2, IgG3, and IgG4 were similar in convalescent sera from all patients. These results provide a possible explanation for the activation of the serum complement system which precedes onset of shock in severe dengue infections.

Development of a simple indirect enzyme-linked immunosorbent assay for the detection of immunoglobulin M antibody in serum from patients following an outbreak of chikungunya virus infection in Yangon, Myanmar

During 1984, 1548 children were admitted to the Yangon [Rangoon] Children's Hospital in Myanmar [Burma] with haemorrhagic fever. No evidence of recent dengue infection was found in 577 of the 803 children from whom paired sera were obtained, raising the possibility of reappearance of Chikungunya virus infection in Myanmar. An enzyme-linked immunosorbent assay (ELISA) for the detection of anti-Chikungunya virus immunoglobulin M (IgM) antibody was prepared and standardized using only reagents which are commercially available or which could be prepared without the use of sophisticated equipment. While there was 90% agreement between haemagglutination inhibition (HI) tests and the IgM ELISA in the diagnosis of acute Chikungunya virus infections, 12 additional patients with stationary anti-Chikungunya virus HI antibody titres could be identified as having acute Chikungunya infections using the ELISA. Furthermore, the ELISA could identify twice as many patients (31/103) at the time of admission to hospital as the HI test (15/103). There was no false positive IgM reaction with the ELISA which could be attributed to the presence of rheumatoid factor. Using the test, 103 of a sample of 163 children who presented to the Yangon Children's Hospital with fever/haemorrhagic fever were diagnosed as Chikungunya patients, 4 had possible dual Chikungunya and dengue infections, 16 had dengue, 30 had neither Chikungunya nor dengue infections, and a definitive diagnosis could not be made for 10 patients. Routine use of the ELISA would alert authorities to future outbreaks of Chikungunya virus infection and avoid admission to hospital of patients with a non-life-threatening viral disease.

Study of vector, amplifier, and human infection with Japanese encephalitis virus in a Rangoon community

A prospective serologic study was undertaken in a Rangoon community in 1982 to quantify Japanese encephalitis virus infections in humans and in pigs. The prevalence, relative abundance, and host preference of Culex mosquitoes in the area were also determined. Japanese encephalitis virus infection was detected in 52.1% of the pigs, although concurrent human Japanese encephalitis virus infection was not detected. The known Japanese encephalitis virus vector mosquito species were prevalent in the study area. Host preference determination for the Culex species revealed that they were zoophilic and that the most frequent hosts were cows. The absence of concurrent human Japanese encephalitis virus infection in the presence of Japanese encephalitis virus infection in pigs and of vector mosquito species is discussed.

Pilot sero-epidemiological survey on Japanese encephalitis in north-western Burma

A pilot sero-epidemiological survey of Japanese encephalitis was carried out in three areas of north-western Burma applying the hemagglutination-inhibition test. The existence of Japanese encephalitis infection in these areas was confirmed and its incidences in these areas were estimated and compared graphically.

Hemagglutinin prepared from cells of Aedes albopictus, clone C6/36, infected with type 1 dengue virus

A high titer of hemagglutinin (HAnin) was found in culture fluids of cells of Aedes albopictus, clone C6/36, infected with type 1 dengue virus. The HAnin (TC antigen) was associated with complete virions and no appreciable small-sized HAnin was produced, in contrast to the case in an infected suckling mouse brain (SMB) homogenate, in which most of the HAnin is smaller than complete virions. Extraction of the TC antigen with Tween 80-ether disrupted the HAnin into smaller-sized particles, resulting in complete loss of infectivity (TE-TC antigen), but it did not affect the titer or reactivity of the HAnin. Comparative hemagglutination-inhibition (HI) assay of human sera using TC antigen, TE-TC antigen or standard antigen extracted from infected SMB (SMB antigen) showed that TC or TE-TC antigen could be used for routine diagnostic or epidemiological HI tests instead of SMB antigen, which is rather hard to prepare.

Changes in dengue and Japanese encephalitis (JE) antibody after JE vaccination

Serological studies before and after Japanese encephalitis (JE) vaccination were made on subjects of various ethnic groups with or without dengue and/or JE antibodies. In these subjects dengue and JE hemagglutination-inhibition (HI) and neutralization (N) antibodies were measured. Seroconversion to JE was observed in about 45% of the subjects by the HI test and 63% by the N test, whereas seroconversion to dengue with only 4-fold increase in titer after vaccination was detected in 14% by the HI test and in a single case (3%) by the N test. The presence of JE and/or dengue antibody in the prevaccination sera did not significantly influence the seroconversion rates of JE-HI and N-antibodies after vaccination. Moreover the seroconversion rate did not seem to vary markedly in different ethnic groups, although tendencies for subjects from Southeast Asia to have dengue antibodies and Japanese people to have JE antibodies were demonstrated. The presence of dengue N-antibodies in the prevaccination sera did not significantly influence the geometrical mean titer of postvaccination JE-N antibody. Thus the antibody response to JE vaccination was fairly specific to JE, and no marked secondary response was observed.

Epidemiological features of dengue and chikungunya infections in Burma

A serological survey for antibody to dengue and chikungunya was carried out in all 14 divisions and states and 2 border towns in Burma during 1973-74. Dengue HI antibody prevalence rate of less than 10% was observed in Arakan and Shan States, 10 to 30% in the Irrawaddy, Pegu, Mandalay Divisions and Kachin, Mon and Karen States, 31 to 60% in Sagaing Division, and over 60% in Rangoon, Magwe and Tenasserim Divisions. Similarly, chikungunya HI antibody prevalence rate of less than 10% was observed in Arakan State, 10 to 30% in the Irrawaddy, Pegu, Mandalay and Sagaing Divisions and Kachin State, 31 to 60% in Rangoon Division and Mon State. Both dengue and chikungunya antibodies were detected where Aedes aegypti mosquitoes were prevalent but the antibody prevalent rates were not directly proportional to the premises index. No HI antibody to dengue nor chikungunya was detected in Aedes aegypti free hilly areas, Chin and Kayah States, but was detected in the Shan State, Dengue and chikungunya infections were observed both in rural and urban populations. Dengue and chikungunya infections affected all socioeconomic classes in Rangoon equally but in Mandalay high socioeconomic class was nearly 3 times less affected than lower socioeconomic class. The infrequencies of dengue and chikungunya infections were observed to be 2 to 3 times higher in residents of Rangoon City than those of other towns. In Rangoon the antibody prevalence rates to dengue increased progressively with age while in other towns no appreciable increase in rates with age was observed. Both sexes were equally affected. This study provides strong circumstantial evidence that dengue and chikungunya viruses are highly and widely distributed throughout Burma, and that new outbreaks of haemorrhagic fever could occur in previously free areas following introduction of dengue viruses into populations previously exposed to one type of dengue.