Epidemiological analysis of hepatitis A morbidity

A retrospective epidemiological analysis of hepatitis A morbidity for many years among the population of two neighboring towns in the temperate climatic zone of the USSR has revealed the cyclic character of the epidemic process without a perceptible decrease in its extensiveness and has determined the high-risk groups, as well as the beginning of the seasonal rise of morbidity in these groups. The results of the study indicate that different levels of hepatitis A morbidity and risk groups can be observed in these two neighboring towns. At periods of a lower morbidity level the high-risk group embraces schoolchildren, and when morbidity is at a higher level the risk group includes schoolchildren and preschool children in organized groups. Among the latter the morbidity level is influenced by factors acting all the year round and among school children, by seasonal factors. The beginning of the seasonal rise of morbidity falls on August, while in organized groups of children of preschool age the seasonal rise of hepatitis A morbidity begins 1-1.5 months later. All prophylactic measures for controlling hepatitis A should be carried out with due regard to these features of the epidemic process.     

Seroprevalence of antibodies to hepatitis A and E viruses in pediatric age groups in Turkey

Hepatitis A and hepatitis E are enteric transmitted viral diseases occurring in epidemic and sporadic forms especially in developing countries. Previous studies in Turkey showed that most residents are infected with HAV by the second decade of life. Since HEV is generally transmitted by the same route as HAV we conducted a community-based seroprevalence study for HAV and HEV infection in Ahatli area in Antalya, Turkey where socioeconomic conditions are low. Anti-HAV total immunoglobulin was tested by using a microparticle EIA (Axsym-Abbott Lab). Anti-HEV IgG was assayed by a micro ELISA method (Genelabs-Singapore). Of the 338 sera tested, 112 (33.1%) were positive for anti-HAV total antibody. Anti-HEV IgG was detected in three (0.89%) of the serum samples. Seropositivity rates of HAV in preschool and school children were 19.9% and 43.9% respectively (p < 0.001). No antibody to HEV was detected in preschool children, while the prevalence of anti-HEV IgG was 1.6% in children attending school. Our data showed that seroprevalence of anti-HAV is high among children samples but HEV infection appears to be relatively rare in pediatric age groups.     

Detection of hepatitis B virus infection markers at a collective

The occurrence of serological markers of hepatitis B virus infection among the members of a newly formed community (370 persons) was determined. The markers were detected with the use of highly sensitive methods for the detection of HBsAg, anti-HBs, HBeAg, anti-HBc, IgM anti-HBc. At the time of the formation of this community HBsAg, anti-HBs and anti-HBc were detected, respectively, in 4%, 11% and 31.3% and 6 months later, in 8.4%, 9.5% and 46.4% of persons. The presence of a considerable number of inapparent forms of hepatitis B and differences in the degree of the involvement of individual groups in this community into the epidemic process have been shown.     

The spread of HB virus infection in familial foci in a territory hyperendemic for hepatitis B

Epidemiological surveillance with the use of highly sensitive techniques for the indication of markers of hepatitis B (HB) virus infection in their dynamics has made it possible to find out that at a territory, hypersensitive for HB, along the existing high risk of this infection as the result of parenteral medical manipulations the intensive natural transmission of HB virus infection occurs under the conditions of everyday contacts with sources of the infection, patients with chronic forms of HB virus infection being of the highest epidemic importance. Under these conditions, children aged up to 7 years have been found to belong to the highest risk group. As a consequence, children of this age should be covered in future by specific preventive measures against HB. The spread of the epidemic process of HB virus infection in family foci is usually manifested by anicteric (usually not diagnosed) forms of this infection. All these circumstances make it expedient to develop antiepidemic and prophylactic measures in the foci of HB.     

The epidemiological differential diagnostic signs of viral hepatitis A and viral hepatitis E]

A retrospective epidemiologic analysis of cases diagnosed as hepatitis A (HA) has been made in territories characterized by high intensity (4 towns in Central Asia) and low intensity (Novomoskovsk, Tula Province) of the epidemic process development. Morbidity structures for different age and social groups of the population, as well as the morbidity time course, both annual and over many years, were analyzed over 1973-1986. Specific features in the development of the epidemic process in HA and hepatitis E (HE), formerly called hepatitis non-A, non-B with the fecal/oral mechanism of the infection transmission, were studied. Twelve epidemiological differential diagnostic signs of these two infections were formulated, classified, and validated. Contribution of centralized water supply and sewage systems to the development of HE epidemic process and the regulating role of infectious immunological mechanisms in the development of HA epidemic process were demonstrated.     

Structural dynamics of strains of a hepatitis B virus population in the Ukraine and its etiological prognosis

Changes in the population structure of influenza B virus in the Ukraine since 1980 has been studied. New strains of the virus have been identified and the epidemic potentials of different strains have been compared. The data on the drift mechanism of the origin of the intermediate strains of influenza B virus have been observed. A suggestion on the etiological prognostication of the epidemic process has been made.     

Problems of the epidemiology of viral hepatitis in Ryazan Province

The analysis of some features of the course of the epidemic process of viral hepatitis on the territory of the Ryazan region is presented. Periodic rises and falls in viral hepatitis morbidity, varying in their regularity (4-6 years), have been registered in the region. The general level and the seasonal distribution of viral hepatitis morbidity are determined by the morbidity rate among children, the increase in the proportion of children of senior school age being observed in recent years.     

Monthly dynamics of the epidemic process in viral hepatitis B

Monthly fluctuations in the number of registered cases of acute viral hepatitis B and HBsAg carriership have been studied. The study has revealed that, similarly to other infectious diseases, viral hepatitis is characterized by monthly fluctuations in the intensity of the epidemic process. Such fluctuations are characteristic of all known clinical forms of this infection; they are determined by the specific pathogenetic features of the process and by the ways of the transfer of the virus. The vernal rise of the infection is explained by activation of the manifest and asymptomatic chronic variants of the infectious process and, as the consequence of a rise in the number of asymptomatic cases, by a higher incidence rate of post-transfusion hepatitis infection. The autumnal rise of the infection results from the action of natural factors contributing to the transfer of the virus. Both rises are interrelated and interdependent. The seasonal fluctuations of the epidemic process should be taken into consideration when planning and implementing prophylactic and epidemic-control measures.     

The results of a seroepidemiologic study of Newcastle dysentery

Differences in the monthly distribution in the number of seropositive individuals among children and adults in years with different intensity of the epidemic process have been revealed. Immunity in cases of dysentery caused by S. newcastle reflects the yearly and seasonal activation of the epidemic process in this Shigella infection both in children and adults, the seroconversion characteristics observed in the year of a high morbidity level being a more objective criterion indicating the beginning of the activation of the epidemic process in dysentery caused by S. newcastle in comparison with the commonly registered morbidity level.     

Clinical and epidemiological description of acute intestinal infections in children of the lower Volga region

In accordance with the results of laboratory diagnostics, carried out by bacteriological, serological and PCR methods, the etiological structure of acute bacterial and viral intestinal infections, most frequently occurring in children of the Astrakhan region, is presented. An important role of viral diarrhea cases, prevailing among the total number of cases of intestinal infections in children, is emphasized. The data on the irregular distribution of morbidity by months, especially in viral intestinal infections and salmonellosis with the prevalent involvement of children aged up to 2 years into the epidemic process, are presented. Infections affect mainly children given artificial feeding, as well as those with complicated premorbid state and frequently having acute respiratory viral infections.     

The territorial and age-related characteristics of the distribution of patients with non-A, non-B viral hepatitis infected via the fecal-oral mechanism in foci of elevated viral hepatitis morbidity in the Uzbek SSR

The study of patients from 10 foci of acute viral hepatitides for the presence of HBsAg (in the passive reverse hemagglutination test) and anti-hepatitis A virus IgM (in the radioimmunoassay) has shown high frequency and variability in the spread of hepatitis non-A, non-B, the prevalence of adults aged 20-29 years and children aged 2-4 years among persons involved into the epidemic process and the tendency towards an increase in the proportion of hepatitis non-A, non-B in the total number of cases of viral hepatitides in the republic.     

Late observations in a familial foci of hepatitis B using a full set of specific markers of the infection

The complete set of specific markers of hepatitis B has been identified, thus making it possible to evaluate the spread of this infection in family foci, as well as the intensity and dynamics of the epidemic process, under the conditions of prolonged observations. The study has shown that the spread of hepatitis B infection is determined by the presence of HBeAg in antigen-positive patients with viral hepatitis B and HBsAg carriers.     

Controversial and unsolved problems in the prevention of infectious hepatitis]

Data are presented indicating that 1 ml of 10% and 1% immunoglobulin possessed similar epidemiological activity in the prophylaxis of infectious hepatitis. It was shown that redical action of infectious hepatitis on the epidemic process was possible only in case of embracement by immunoglobulin vaccination of not less than 80% of children aged from 1 to 11 years. The economic effect of the introduction of 1% immunoglobulin constituted about 40 000 roubles per 100 000 persons vaccinated. Besides, a possibility of side-effects were nilin case of placental immunoglobulin since in the 1% preparation nonspecific biologically active substances could penetrate in much lesser amounts.     

Various epidemiological principles of the spread of viral hepatitis in the Astrakhan district]

Analysis of many-year changes in the vitral hepatitis incidence in the Astrakhan region showed a significant cyclicity of the epidemic process: its incidence rose 4 times during the period of from 1957 to 1976; four of these elevations were comparatively high (in 1960, 1964, and 1974). Lately the group of children aged from 3 to 7 years has been of the greatest epidemiological significance, but at present greatest incidence of the disease fell on the group of persons aged from 8 to 14 years. This can be connected with gamma-globulin vaccinations given to children aged under 10 years. Seasonal distribution of morbidity in different are groups was about the same and reflected the general automn-winter seasonal prevalence.     

Specific features of the HIV infection epidemic in Moscow

Retrospective analysis of the epidemic of HIV infection in Moscow allowed to mark out two periods: the first--from 1987 to 1993 and the second one--from 1994 to 2000. The characteristic feature of the first period of the epidemic was the sexual transmission of the agent mainly among homosexuals; the most affected group were persons aged 20-39 years and the number of AIDS patient decreased with a simultaneous growth in lethality. During the second stage of the HIV infection epidemic changes in the prevailing transmission routes of the agent occurred: injection drug addicts took the leading role. Changes in the ratio of HIV-infected men and women took place along with active involvement of persons aged 13-18 years into the epidemic process. The established changes in the epidemiological situation require corrections in the strategy and tactics of epidemic control and prophylactic measures.     

The epidemic process as a system. I. The structure of the epidemic process

A new epidemiological concept (socio-ecological) has been formulated on the basis of the principles of the theory of systems and the theory of information. In accordance with this concept, the epidemic process is organized on the same principle as living matter, and the stability of this process at all levels of its organization is ensured by the processes of self-regulation. The conditions of the life of human society have been shown to be organically incorporated into the structure of the epidemic process as a regulating subsystem on the socio-ecological level.     

Retrospective detection of a subclinical hepatitis A virus (HAV) epidemic affecting juvenile cohorts of the Hungarian population

Sero-epidemiological surveys of serum samples taken in 1982, 1987, 1994 and 1999 have been performed with hepatitis A virus-specific (HAV-specific) serological tests. Results obtained during these surveys show that the proportion of seropositive blood donors decreased from 69% to 18% within 17 years. The authors have recognised a (mainly subclinical) epidemic, affecting about 115000 teenagers in 1992-1994 in Hungary, is a threatening phenomenon. It was calculated that only about 3600 clinical diseases were associated with the epidemic, recognised retrospectively from the findings of the four sero-epidemiological surveys. Epidemiological data indicated that the excess clinical diseases caused by HAV concentrated in the southern counties of Hungary, which have been affected by the social and military activities between 1992 and 1994. Due to the decrease of subjects seropositive for HAV, sera from preselected or actively immunised donors will be required in the future and vaccination against HAV with killed virus is likely to be recommended for risk groups. Furthermore, health authorities might promote active immunisation of young children against HAV infection; for that, promotion of manufacturing combination vaccines of HAV/HBV/DPT or, for certain countries, HAV/DPT would be desirable.     

Multiyear and seasonal hepatitis A morbidity in different population age groups in certain areas

At the areas with high activity of hepatitis A (HA) epidemic process the duration of epidemic cycles was shown to differ, the intervals between the peaks of morbidity increasing in older age groups. The beginning of seasonal rises exceeding the average annual HA morbidity level in different age groups was found to depend on the activity of the epidemic process. At the areas with the highest activity of the epidemic process children aged 1-2 years were the first to be affected by the seasonal rise of HA. Stable direct correlation between HA morbidity levels at the beginning of seasonal rises and some markers indicative of unfavorable sanitary conditions (the size of the fly population, the purity of water samples deviating from the requirement of the Government Standard) during the preceding year was demonstrated.     

Diurnal rhythm of the total antioxidant activity of saliva of children with chronic viral hepatitis

The diurinal rhythms of a total antioxidant activity of a saliva were investigated depending on activity of the inflammatory process in a liver of children with chronic virus hepatitis HBV and HCV. The circadian rhythms were found desynchronized, which was showed in lowering of the mesor value, oscillations amplitude, and a rhythm inversion and transformation, as an additional biorhythmological criterion of the presence of the chronic hepatitis of a viral etiology. A tendency of a circadian rhythm to remain with a daily acrophasis but with a law level of amplitude oscillations and a mesor was to be observed after the treatment of children with inactive HBV. By an active HBV a circadian rhythm with it's inversion has been renewed. It was determined the remaining of an ultradian rhythm with increasing level of amplitude oscillations after the treatment of inactive HCV. The law amplitude oscillations and a insignificant increasing of a meror level were characteristic for the circadian rhythm of total AOA of the children with active HBV. It was proved the possibility of usage of the biorhythmological parameters of diurinal rhythms of total AOA as a criteria of efficiency of the conducted therapy for the given group with disease children.     

Epidemics in nonrandomly mixing populations: a simulation

Two stochastic, discrete-time simulation models for the spread of an epidemic through a population are presented. The models explore the effects of nonrandom mixing within the population and are based on an SIR epidemic model without vital statistics. They consider a population of preschool children, some of whom attend child care facilities. Disease transmission occurs both within the home neighborhood and at the child care facility used, if any. The two models differ in population size used, population density, the proportions of children using different kinds of care, and the functions used for calculating the probability of disease transmission. Results are presented for seven different variables--length of the epidemic in weeks, number of cases, number of cases in each kind of care (two day care centers, private homes, and children staying at home), and the number of private home providers affected by the epidemic. In addition, the distribution of total epidemic size and the progress of an epidemic are estimated from 25 epidemic trials. The effects of the location of homes of initial cases, the type of care used by initial cases, and the density of the population are discussed. Results from the simulation confirmed the importance of type of care on the risk for disease transmission. Results from all runs of the simulation showed that children who attended a day care center were most likely to become infected, children who went to a private home were intermediate, and children who did not use any day care facility were at the lowest risk. The size and length of the epidemics were related to the presence of the disease in day care centers, regardless of the location of the initial case, and the time at which the disease entered the center(s). The simulations also showed that the geographical distribution of the homes of children attending a particular center was a critical feature involved in the production of epidemics. The center with more widely distributed homes of students was less likely to experience a major epidemic than the center with clustering of student's homes within a neighborhood. This indicates that it is not simply attendance at a day care center that is critical for disease spread, but that the nature of the population of children attending a center is also of critical importance in the actual risk for disease spread within the center. These results are discussed with reference to the spread of hepatitis A among day care centers in Albuquerque, New Mexico.