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.

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.

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.

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.

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.

Prevalence of HTLV-III/LAV antibody in selected populations in Thailand.

Antibody to the human T-lymphotropic virus, type III/lymphadenopathy-associated virus (HTLV-III/LAV) by ELISA test was detected in one (1%) of 101 male homosexual prostitutes (confidence limit 95%:0.03-5.4%, in two (2%) of 100 thalassemia patients, and in none (C.L. 95%:0-3.6%) of 100 female prostitutes, 99 parenteral drug abusers, 100 male VD patients, 100 consecutive blood donors in serum collected from February through June 1985. Serum from the positive homosexual subject was strongly positive on repeated ELISA testing, and was also positive by Western Blot test. The two thalassemia patients, who were repeatedly weakly-positive by ELISA, were negative by Western Blot test and presumed to be false positive reactors. Prevalence of HTLV-III/LAV virus in sexually-active homosexuals in Thailand in 1985 appears to be similar to the 1% rate among homosexuals in San Francisco in 1978 at the start of the AIDS epidemic there.