A review of Hib epidemiology in Asia.

Meningitis due to an invasive Haemophilus influenzae type b (Hib) infection, has been previously perceived to be relatively uncommon in Asia. However, the incidence of disease and its impact may have been underestimated. In addition to a lack of microbiological facilities in some hospitals, difficulties in culturing the organism and the widespread use of antibiotics may have hidden the true incidence of the disease in some countries. Furthermore, the reported disease burden probably underestimates the incidence of Hib pneumonia. The epidemiology of invasive Hib disease for various Asian nations is reviewed in this paper. Hospital-based studies show that Hib is a major cause of bacterial meningitis and/or pneumonia in the Philippines, India, Thailand, Malaysia, Indonesia and Vietnam. Singapore and Hong Kong have a low incidence of infection compared with Western and other Asian nations. This low incidence is not due to a higher level of natural protective antibodies, but may be related to an interaction between environmental and genetic factors. Therefore the widespread belief that Hib infection is unimportant in Asia does not refer to Asia as a whole and possibly to Chinese patients only, and failure to recognize this has serious implications. The inclusion of Hib vaccine in the routine infant immunization schedule in many industrialized nations has significantly reduced the incidence of invasive disease. Recent studies have shown Hib vaccination is also effective in preventing invasive disease in children in developing countries. While population-based data may be required to confirm the need for public-funded infant Hib immunization in Asia, its introduction in countries with a high incidence of Hib meningitis and/or pneumonia has the potential to significantly improve pediatric health and survival.

Hepatitis A virus: declining seroprevalence in children and adolescents in Southeast Asia.

The prevalence of hepatitis A virus (HAV) in a country largely reflects its standards of hygiene and socioeconomic conditions. Countries which undergo socioeconomic development show major change in HAV prevalence from high to low endemicity, and this is largely reflected in patterns of age-related seroprevalence. This paper presents age-related HAV seroprevalence patterns of SE Asian countries, and highlights how these patterns have changed over recent decades. Singapore, Thailand and Malaysia have experienced a decline in childhood and adolescent HAV seroprevalence, typical of countries which undergo socioeconomic development. By contrast, India has remained a country of high endemicity, with almost universal seroconversion in childhood. The Philippines and Vietnam show age-related seroprevalence patterns typical of high to moderate endemicity, while Indonesia shows significant regional variation in HAV seroprevalence. Populations within countries which exhibit major improvements in endemicity and age related HAV seroprevalence patterns are at risk of HAV epidemics, and a paradoxical increase in incidence tends to occur as seroconversion shifts from children to adults. The residents of these countries, a significant number of whom are at-risk, would benefit from a program of vaccination, as would non-infected individuals visiting high-risk areas.

Integration of hepatitis B vaccination into the expanded programme on immunization in Chonburi and Chiangmai provinces, Thailand.

Hepatitis B (HB) immunization was introduced as part of the expanded programme on immunization (EPI) in two provinces in Thailand and evaluated over a four year period. Three doses of HB vaccine were offered to 60,980 newborns at birth, 2 and 6 months of age. The overall coverage for complete HB immunization was 90.4%. Serosurveys of randomly selected children under the age of 5 years were undertaken before and at the end of the project. Levels of HBsAg positivity were reduced by 85%, and there was a corresponding 70% increase in protective immunity. These findings demonstrate that HB immunization can be successfully integrated into EPI without adverse effect on coverage rates of other antigens, and results in a marked reduction in the rate of chronic carriage of HB virus in preschool age children.

Seroprevalence of anti-HCV among HIV-infected persons and general population.

From November 1993 to December 1994, the seroprevalence of anti-HCV, HBsAg was studied among 346 HIV-infected persons (asymptomatic HIV-infected persons and AIDS patients) and 1,023 subjects from the general population (including 119 cord blood samples). The prevalence of anti-HCV, HBsAg among HIV-infected patients aged 15-45+ years was 11.0 and 11.6 per cent respectively which is significantly higher than the comparable levels for the general population (1.9% and 4.7%) in the age group 15-44 years. There was no statistically significant association of anti-HCV and HBsAg prevalence among 200 asymptomatic HIV-infected carriers and 146 AIDS patients. Assays for anti-HCV among blood donors are highly recommended to reduce the development of liver disease or cirrhosis in the immediate future.

Impact of Thailand's HIV-control programme as indicated by the decline of sexually transmitted diseases.

The Thai government began an HIV-control programme in 1989. The programme had the following parts: the government bought and distributed sufficient condoms to protect much of the commercial sex in the country; sanctions were brought against commercial sex establishments where condoms were not used consistently; and a media campaign bluntly advised men to use condoms with prostitutes. Between 1989 and 1993 the use of condoms in commercial sex in Thailand increased from 14 to 94%, according to surveys of prostitutes, and the number of cases of the five major sexually transmitted diseases declined by 79% in men. We estimate that sex acts with prostitutes where there was a risk of HIV transmission declined from about 2.6% in June, 1989, to about 1.6% in June, 1993. If condom use in commercial sex stays high, future cohorts of young men and women may experience lower HIV incidence rates than those of the recent past. However, although condom use is high, there are many more infected prostitutes than before and many infected men who will pass HIV to their wives.

Protection against hepatitis A by an inactivated vaccine.

OBJECTIVE: To evaluate the safety and efficacy of a new inactivated hepatitis A vaccine. DESIGN: Double-blind randomized controlled trial stratified by community. SETTING: Community-based in Thailand. STUDY PARTICIPANTS: A total of 40,119 children, aged 1 to 16 years, attending 148 primary schools: 38,157 (95%) entered surveillance a mean of 138 days after receiving vaccine dose 1; 33,586 (84%) completed the controlled trial of 532 days; and 31,075 (81%) received crossover vaccine and remained under surveillance until day 844. INTERVENTION: Participants received hepatitis A vaccine or control hepatitis B vaccine starting January 7, 1991 (doses in months 0, 1, and 12), and crossed over to the alternate vaccine 18 months later. MAIN OUTCOME MEASURE: Cases of hepatitis A (symptoms, alanine aminotransferase levels of 45 U/L or higher, and IgM to hepatitis A virus) were identified by evaluating school absences of 2 or more days. RESULTS: There were no serious adverse reactions despite administration of more than 109,000 doses of hepatitis A vaccine. Among initially seronegative recipients of two doses of hepatitis A vaccine, the proportion with 20 mIU/mL or more of antibody to hepatitis A virus before and 5 months after a 1-year booster was 94% and 99%, respectively. Of 6976 episodes of illness during the controlled trial, there were 40 cases of hepatitis A; 38 were in the control group. Of the 40 cases, six, all in controls, occurred after the 1-year booster dose. Following two doses of hepatitis A vaccine (days 138 through 386), protective efficacy was 94% (95% confidence interval, 79% to 99%); cumulative efficacy including the postbooster period (days 138 to 532) was 95% (95% confidence interval, 82% to 99%). The two hepatitis A vaccine recipients who had symptomatic infections (257 and 267 days after dose 1) appeared to have been partially protected since their illnesses were brief and associated with only slight increases in alanine aminotransferase. CONCLUSIONS: Inactivated hepatitis A vaccine is safe; when administered in two doses, it protects against hepatitis A for at least 1 year.

A cholera outbreak associated with eating uncooked pork in Thailand.

In a village near Chiangmai, Thailand, during October 1987, there was an outbreak of cholera following a funeral in which 264 attendants were served food. The present article is a report of an epidemiological study performed to identify the source of infection and the mode of its transmission. All the attendants were screened for infection by bacteriological examination of their rectal swabs and were kept under diarrhoeal surveillance. Of them, 20 patients and 40 matched controls were interviewed about the details of their eating foods served at the funeral. Vibrio cholerae 01, Inaba, El Tor was detected from 24 persons (9.1%), 15 of whom suffered from mild diarrhoea and the rest 9 had inapparent infections. There was no death. Except one butcher whose rectal swab was positive for the same strain of V. cholerae, 3 other butchers and 4 women who had prepared food were free from the infection. Food remnants were not available for culture. The water used for cooking and the water from the cement well used for slaughter were negative for the organism. The only significant association (p less than .01, odds ratio = 15) was found between an attack of cholera and eating laebmoo--an uncooked pork preparation with Thai spices and chili. The transmission of cholera appeared to have occurred through eating the uncooked pork presumably due to its contamination with V. cholerae shed by the infected butcher. He was known to have earlier visits to Chiangmai where cholera epidemic was going on.

Thailand Expanded Program on Immunization: a ten-years review of coverage and impact on EPI target diseases.

The national immunization coverage in Thailand for all types of vaccine has been steadily increasing since 1978, when the EPI was formally launched. The coverage in 1987 was 96% for BCG, 75% for DPT, 74% for OPV, and 60% for TT. Measles vaccine, which started only in late 1984, had the lowest coverage, 51%, in 1987. During the period 1982-1987, the drop-out rates between the first and third dose of DPT and OPV decreased dramatically from 69% to 13% and from 42% to 13% respectively. Sampling surveys of immunization coverage showed higher coverage for DPT and OPV than those from reporting in all regions, especially in the capital city which has a high concentration of the private health sector. Only the northeastern region had less coverage from surveys than from reporting. Following the launch of EPI, the disease incidence demonstrated a clearly downward trend for diphtheria, poliomyelitis, and measles, while in the case of pertussis and neonatal tetanus, slower of still fluctuating declines were observed. The reported age-specific incidences per 100,000 population in 1986 for children 0-4 years were as follows: 4 for diphtheria, 0.9 for poliomyelities, 180 for measles, 14 for pertussis, and 10 for tetanus.

Surveillance of neonatal tetanus in Thailand, 1977-1986.

Information on the morbidity and mortality of neonatal tetanus was reviewed to evaluate the impact of the immunization programme among pregnant women in Thailand from 1977. We also analysed the epidemiological characteristics of investigated neonatal tetanus cases during the period 1984-1986. The neonatal tetanus case rate declined from 72.1 per 100,000 livebirths in 1977 to 53.7 per 100,000 livebirths in 1986. Reduction in the incidence rate was inversely associated with increasing vaccination coverage of pregnant women with tetanus toxoid. The ratio of male to female neonatal tetanus was 1.5 to 1. Approximately 95 per cent of the cases occurred within the first 14 days of life, with the highest number recorded at 6-8 days of life. The majority of investigated cases were infants who became ill following delivery assisted by traditional birth attendants or relatives of mothers. About 88 per cent of these cases were infants whose mothers had no tetanus immunization. Razor blades and bamboo splits were the most frequently used instruments for cutting the umbilical cord. Strategies to control neonatal tetanus in Thailand should include immunization of pregnant women with tetanus toxoid, and more comprehensive training and supervision of untrained birth attendants.

Several sporadic outbreaks of El Tor cholera in Sunpathong, Chiang Mai, September-October, 1987.

From September through October 1987, a cholera outbreak involving 59 cases of biotype El Tor, serotype Inaba occurred in Sunpathong district, Chiang Mai. No cases died. Twenty-seven cases were males and 32 were females. The age ranged between 4 months and 85 years, with a median of 36 years. The outbreak affected 7 small communities, and showed different vehicles of infection. Six housewives and one girl were infected with cholera in the first localized outbreak. The transmission of infection appeared due to the consumption of packed food contaminated by an infected food handler. In the second localized outbreak, 6 young males acquired cholera after eating uncooked fish harvested from a canal contaminated with cholera organisms. Another outbreak of cholera with 24 culture-confirmed cases occurred among guests at a funeral held in one rural village. The source of infection was traced to uncooked pork contaminated from an infected butcher: Early detection of infected persons, rapid identification of possible vehicles of transmission, and prompt implementation of control measures effectively curtailed the extension of these outbreaks.

An outbreak of nosocomial cholera in a 755-bed hospital.

From 30 October to 7 December 1984, an outbreak of nosocomial cholera involving 11 cases of biotype El Tor, serotype Inaba, took place in a 755-bed hospital in southern Thailand. The outbreak occurred primarily among patients admitted with severe illness. Of the 11 cases, 7 were children and 4 were adults. Most cases had mild symptoms of cholera and no case died in this outbreak. The first 2 cases occurred sporadically with a subsequent cluster of cases showing an explosive pattern. A case-control study found that a history of receiving liquid tube-fed diet was significantly more common among cholera cases than their matched controls, but it could not be determined how the diet was contaminated with cholera. Cases were also significantly more likely than controls to be on oral antacid medication which could increase risk of infection by neutralizing gastric acidity. No additional cases occurred after extensive implementation of control measures.

Foodborne disease outbreaks of chemical etiology in Thailand, 1981-1987.

A study was conducted to determine the current situation of chemical foodborne outbreaks in Thailand for the period 1981-1987. Seventy-three outbreaks of chemical poisoning involving 1236 persons of whom 54 died were reported. Twenty outbreaks affecting 722 cases were caused by insecticide poisoning and methomyl was the most commonly recognized insecticide involved. Poisonous plants were responsible for 43 outbreaks with 420 cases. Mushroom poisoning was the most common entity (21 outbreaks, 211 cases), with plant seed poisoning next (9 outbreaks, 179 cases). There were 8 outbreaks following consumption of poisonous seafoods. Mussels were identified to be the vector in the outbreak of PSP. Horseshoe crabs which served as the vehicles for 4 outbreaks were also suspected to be associated with PSP. Puffer fish accounted for the remaining 3 outbreaks involving 6 cases of tetradotoxin poisoning. More complete reporting and more effort in outbreak investigations are needed for appropriate preventive and control measures.

The Thai expanded programme on immunization: role of immunization sessions and their cost-effectiveness.

A cost-effectiveness study of the Thai expanded programme on immunization was carried out in district hospitals and health centres in Thailand during early 1987. The total annual spending on immunization was US $3852 in hospitals and US $813 in health centres. The percentage distribution of annual costs was similar in both facilities. Salaries were the largest component, followed by building and vaccine costs. The frequency of immunization sessions was the most important factor in determining total costs--immunization costs increasing with the frequency of sessions. In hospitals the average number of fully immunized children was 184, compared with 49 in health centres. The cost per fully immunized child varied widely from US $5.30 to US $33.20, and the most cost-effective facilities were those that immunized the greatest number of children. With the present number of health facilities in all areas of the country, which correspond to saturation levels, the most likely way for the Thai programme to reduce costs would be to make better use of staff time by decreasing the frequency of the services offered, thereby increasing the efficiency of each session. Hospitals should adjust the frequency of their immunization sessions according to the number of children being served, but health centres should offer sessions only monthly or once every two months.

PIP: A cost-effectiveness study of the extended immunization program in Thailand surveyed data from 4 provinces for the fiscal year of 1986. The study's objective was to better use scarce health resources especially in difficult economic times. The survey assessed the total annual spending for hospitals and health centers in U.S. dollars: $3,582 in hospitals and $813 in health centers. In relation to the number of 1 year old children in their respective area, hospitals showed 100% coverage of immunization and not more than that. The vaccine was administered in predetermined clinics that also continued with supplementary outreach activities. The immunization costs for each child was $13.80 in hospitals and $11.80 in health centers and $8.90 and $10.30, respectively for pregnant women. Higher administrative and construction expenses caused hospitals to have higher immunization costs than health centers. Salary was identified as the major factor in both operating and total costs. The output and coverage in hospitals was better than that of centers. Higher hospital costs could be justified by the frequency of immunization and the service load. The hospital immunization sessions should be organized according to service load with the frequency increasing with the number of children. Potential factors such as a decrease in birth rate and the change-over of users to local care should be considered in future studies of immunization coverage and effective health facility use.

Dengue haemorrhagic fever in Thailand, 1987.

In 1987, situation of DHF in Thailand was the worst for the past 30 years. There were 152,840 cases and 785 deaths from the preliminary report. The incidence was highest ever reported. Outbreak begun early in January and reached its peak in July. All 73 provinces were affected except six provinces which had incidence of less than 60 per 100,000 population. The highest attack rates were in school children, especially 5-9 year olds. Virus isolation in a north-eastern province recovered Den-3 and Den-2 more common than other serotypes. Although a large outbreak in 1987 is unlikely to happen in 1988 but with the endemic areas all over the country there is a potential for small outbreaks to occur. The Ministry of Public Health needs new approaches and increased resources to control this disease.

Surveillance of food poisoning outbreaks in Thailand 1981-1986.

In the period of 1981-1986, eighteen outbreaks of food poisoning following ingestion of insecticide contaminated food were reported to the Division of Epidemiology, Ministry of Public Health. There were 678 individuals experiencing illness, of which 9 cases died. Out of 18 outbreaks, 16 involving 615 cases resulted from carbamate (Methomyl and Propoxur) intoxications. The remaining two outbreaks were caused by organophosphate (Coumaphos) and organochlorine (DDT). The case fatality rate was much higher with Coumaphos than Methomyl; and no death was reported among Propoxur and DDT victims. Desserts and beverages were found to be the main vehicles, and private home was the most common place for the outbreaks of food poisoning caused by ingestion of insecticide contaminated food.

A high incidence of neurological complications following Semple anti-rabies vaccine.

A study was conducted to determine the incidence of neurological complications among a cohort of 6,980 recipients of Semple vaccine administered in Bangkok and 5 nearby provinces in 1984. A review of all patients admitted to public hospitals in these 6 provinces discovered a total of 32 cases, with neurological complications following Semple vaccine. Twenty-two cases (68.8%) were encephalitis or myelitis. The complication rate was 3.6 times higher for males than females and the rate was lowest in the 0-14 year age group. Vaccinees receiving large daily dose of vaccine had a higher rate of complications than those with low dose regimen. One patient died, giving the case-fatality rate of 3.13 per cent. Since the search was limited, the rate of neurological complications to Semple vaccine was a minimum of 4.6 cases per 1,000 vaccinees [1:220]. This complication rate was much higher than most rates reported previously. It is imperative to find economically feasible alternatives to Semple vaccine.

Surveillance of food and waterborne diseases in Thailand, 1979-1984.

National surveillance of foodborne diseases in Thailand has revealed an increasing incidence of from 29/100,000 population in 1979 to 74/100,000 in 1984. A total of 158,482 cases and 241 deaths were reported during this 6 year period. In each year, foodborne diseases occurred regularly in April-June. The highest mean annual reported rates were from the North-eastern region, followed by the Central region and the Northern region. Because of inadequate investigations, only 7% (10,567) of the total cases had known specific aetiology. Of these 10,567 cases, the majority (7788, 73%) were caused by micro-organisms which included bacteria (46%), parasites (12%), and viruses (15%), the remaining (2779, 27%) were caused by poisonous plants (19%), animals (1%), and chemicals (7%). In recent years surveillance has increasingly served as a means to control the outbreak. However, due to many limitations, the surveillance data presented here probably do not represent an accurate picture of the whole problem. Two very important factors identified are under-reporting and inadequate case and outbreak investigations.