Several outbreaks of hepatitis A occurred in Norway in 1995-8. Molecular epidemiology was used to follow the spread of hepatitis A virus in the population. Distinct strains of hepatitis A virus (HAV) were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and subsequent sequencing in serum from patients in different communities at risk of infection. Two HAV strains were detected in an outbreak among 26 men having sexual contact with other men. One of these strains was also detected in a geographically limited family outbreak. The family outbreak was first believed to be acquired abroad. The sequence information linked the two outbreaks, and epidemiological and serological analyses revealed the transmission route. This study demonstrates the importance of molecular epidemiology in outbreak investigation, surveillance and monitoring of hepatitis A in the population.
Intravenous drug abuse is a well-known risk factor for acquiring hepatitis A infection. Among drug abusers most cases are sporadic, but epidemic outbreaks may occur occasionally. In this article we describe an epidemic outbreak including 144 serologically proved cases of hepatitis A among intravenous heroin and amphetamine abusers in Oslo. The outbreak lasted for 11 months. 59 (41%) of the patients were admitted to hospital. One of them died and seven developed severe but reversible acute hepatitis. We also registered 26 cases of hepatitis A among close contacts, 14 of whom were associated with a nosocomial outbreak that affected nurses, fellow patients and relatives. We do not know how the hepatitis A virus was introduced into the abuser population, but the further spread was probably dominated by a combination of faecal-oral transmission and parenteral transmission secondary to sharing needles. Although we were unable to detect hepatitis A virus in confiscated drug samples by means of polymerase chain reaction we cannot exclude that some abusers were infected by injection of contaminated amphetamine.
The growing interest to the study of the processes of the spread of hepatitis A (HA) in big cities of our country has stimulated the development of a new prognostic model at the Gamaleia Research Institute of Epidemiology and Microbiology. The model specifically takes into account a number of factors linked with the dynamics of the development of the disease in 6 stages and some regularities in the seasonal rises of HA morbidity. Quantitative relations in the mathematical model are determined by a system of nonlinear integral-differential equations with the first order partial derivatives and under the integral type boundary conditions, which increases the strictness of modeling of HA. The use of this new model has made it possible to carry out the prognostic-analytical study of HA morbidity among children in Perm and to evaluate a decrease in HA morbidity due to the hypothetical vaccination of children in spring months.
Data are presented on the retrospective epidemiological serological investigation of episodes of hepatitis-like diseases among plasma donors in Krasnoyarsk. A mixed structure of the focus was established with prevalence of B- and non-A-, non-B hepatitides. Markers of recent infection with HB virus were recorded in 43.6% of sick donors, at the same time no donors had IgM antibodies to hepatitis A evidencing the acute stage or early convalescence. The use of the insufficiently sensitive passive hemagglutination test for HBsAg identification has resulted in incomplete detection of donors-carriers of HB virus.
Type A hepatitis maintains itself in human populations without either an extrahuman or human reservoir. Intestinal carriers do not appear to be epidemiologically important; viremic carriers have not been demonstrated. Person-to-person transmission by the fecal-oral route is the usual mechanism. Epidemic and endemic occurrence is usually recognizable by well-defined characteristics; a "hyperendemic" patern has been documented. In some countries, but not all, the long-term trend of type A disease has been downward in recent years. Type B hepatitis is worldwide in distribution, and capable of maintaining itself by the carrier reservoir. Transmission is by multiple mechanisms, with the percutaneous route still of major importance when adequately defined in terms of subtle exposures. Contact-associated transmission probably occurs by both the oral-oral and venereal routes. The long-term trend of type B hepatitis is unknown, but some evidence suggests an increase in the United States apart from the epidemic associated with drug abuse. The existence of additional viruses of human hepatitis is suggested by data concerning transfusion-associated disease and multiple episodes in the same individual.