Influenza activity in Czechoslovakia and the USSR, 1980-1985

Between 1980 and 1985, Czechoslovakia had experienced 4 and the USSR 3 major influenza outbreaks. Of the 3 epidemic outbreaks in the USSR, 2 were associated with influenza B virus (in the 1980/81 and 1983/84 seasons) and 1 with influenza A virus of the H3N2 subtype. In the USSR, influenza A (H1N1) virus never predominated as a cause of epidemic during the 5 years period. In Czechoslovakia, 2 epidemics (in the 1980/81 and 1983/84 seasons) were due to influenza A (H1N1) virus. The epidemic in the 1981/82 season had two waves of unequal heights and a mixed type B and subtype A (H3N2) etiology; a two-wave epidemic associated with isolates of influenza A (H1N1) and influenza B viruses was also recorded in the 1983/84 season. The influenza A (H3N2) epidemic in 1983 was of explosive character. All influenza viruses circulating in the two countries between 1980 and 1985 were of the same antigenic profile, but were isolated from the epidemics that occurred in different influenza seasons. The virological surveillance revealed strains of virus closely related to drift variants detected from outbreaks in 1977-1979 and the new variants A/Chile 1/83, A/Philippines 2/82, A/Caen 1/84 and B/USSR 100/83.     

The epidemiology of epidemic parotitis in the USSR.

Morbidity from epidemic parotitis in the USSR in the period from 1958 to 1972 ranged within the limits of 266.6 and 521.7 cases per 100 000 inhabitants. A 3--4 years cyclic recurrence of rises and falls in morbidity was observed. The bulk of cases of disease occur in the winter-spring period. In towns, parotitis is registered 3 times more frequently, in the mean, than in rural districts. More than 95% of patients in the USSR consisted of children under 15, while in Moscow, children aged 3--5 years were the most affected group. In Moscow in the period from February 1, 1972 to January 31, 1973, the morbidity in men was 493.2 per 100 000 and in women 339.5 per 100 000 (ratio 1:1.45).     

The clinico-epidemiological characteristics of the course of a mixed epidemic of influenza and respiratory syncytial infection in Novoshakhtinsk in the summer of 1986

In the summer of 1986 the epidemic, whose etiological agents were influenza viruses A (H1N1) and respiratory syncytial virus, was registered among the population of Novoshakhtinsk. In a number of mines 15.3-16.7% of the employees were affected. Influenza viruses A (H1N1) proved to be closely related in their antigenic and biological properties to viruses isolated in the USSR in March-June 1986, as well as to viruses A (H1N1), the etiological agents of the epidemic which developed in the USSR in October-December 1986.     

Influenza epidemics in the USSR and Czechoslovakia in 1979-1984

In this work materials characterizing the appearance and development of influenza epidemic at the territories of the USSR and the Czech Socialist Republic are presented, the common features and differences of the epidemic process in both countries are recorded. The work shows that in both countries the appearance of this epidemic is caused by the same virus. In most cases the epidemic started earlier and lasted longer in the USSR, but morbidity rate during the epidemic was, on the whole, higher in the Czech Socialist Republic. Similarity in the course of the primary period of the epidemic processes from their appearance to their maximum rise was observed. In both countries the maximum rise of morbidity rate was registered on weeks 3-4 from the beginning of the epidemic.     

Epidemiologic analysis morbidity with meningococcal infections in the USSR]

The authors present the analysis of the incidence of epidemic cerebrospinal meningitis in the USSR from 1937 to 1974, and of meningococcus infection from 1965 to 1974. A rise of the meningococcus infection incidence from 1969 to 1974 was recorded 28 years after the elevation of 1940-1942 and was 1.5 times below this latter rise. The rise in 1969-1974 was characterized by marked signs peculiar to the infection with the droplet transmission mechanism; among those who contracted the disease prevalence was seen among children aged under 14 years (63-72%). A marked affection of juveniles was noted. Three types of the dynamic of the meningococcus infection incidence in the republics located in different climatic-geographical zones of the USSR were noted: slow, gradual increase of the level, interrupted and explosive. Such character was determined in the dynamics of the seasonal elevations of morbidity. Antiepidemic measures including a complex of nonspecific measures could not be assessed as sufficiently effective. This finds reflection in the natural course of the epidemic process of the meningococcus infection which remains uncontrolled. From the patients with generalized form of the disease meningococci of group A were isolated in 80-100% of cases, from the number of those typed. The group-specific reference of the nasopharyngeal strains depended on the epidemic situation: strains of serological group A prevailed at the period of the morbidity elevation, and other serological groups (particularly of C and B) increased at its decline.     

The use of programmed microcomputers for retrospective epidemiological analysis]

In this article two programs for programmed microcalculators, models Elektronika MK-61 and Elektronika MK-52, manufactured in the USSR, are presented. These programs permit the determination of indices describing the dynamics of the epidemic process, both annual and for several years.     

The epidemic spread of the influenza A and B viruses in the USSR in 1985-1986

The data on the spread of influenza A and B in the autumn and winter of 1985-1986 are given. Three epidemics caused by all presently circulating viruses, B, A (H3N2) and A (H1N1), were registered in the USSR. Of these, the greatest one was the epidemic of influenza B; morbidity rate among the adult population during this epidemic was at the level with the morbidity rate characteristic of the epidemics registered at the period of 1962-1972, and morbidity rate among children, especially school children, was even higher.     

Antibody responses to influenza vaccines containing A/USSR/90/77.

Studies were undertaken in adult groups aged 17-24 years, 25-64 years and 66-100 years to determine the haemagglutination-inhibiting antibody responses to sub-unit influenza containing A/USSR/90/77 (H1N1). Antibody responses to A/USSR/90/77 were low in all groups. The young adult group (17-24 years) produced a primary response to A/USSR/90/77 and showed a significant response to a second dose of vaccine, whereas their responses to the A/Texas/1/77 (H3N2) and B/Hong Kong/8/73 components were of the anamnestic type and showed no significant increase to a second dose. The adult (25-64 years) and aged (66-100 years) groups responded anamnestically to all three vaccine components. There was no impairment of the antibody response in the aged group in comparison with the response in the adult group. A comparative assay in microtitre trays and WHO plates showed two- to four-fold differences in antibody titre to A/USSR/90/77 in these systems.     

The epidemiological characteristics of meningococcal infection in the USSR

The epidemiological analysis of morbidity in meningococcal infection in the USSR in the period of 1969-1987 showed that the second rise of the morbidity level occurred in 1984 and was followed by its decrease in most of the regions of the USSR. This study also revealed that the characteristic feature of the second rise of morbidity in meningococcal infection was a considerable involvement of young children (aged up to 3 years), as well as the increased etiological role of group B meningococci in cases of meningococcal infection and the circulation of these microorganisms among the population. Besides, the preservation of the etiological importance of group A meningococci in many regions of the USSR, especially among adults, was noted. In this connection, the use of Soviet group A meningococcal polysaccharide vaccine on epidemiological indications was considered to be epidemiologically substantiated.     

Nature of the epidemic process in Sonne and Flexner dysenteries and the causes of its induction

A comparative study of the epidemic process in Sh. sonnei and Sh. flexneri dysentery in different regions of the USSR revealed that the morbidity level of Sh. sonnei dysentery changed simultaneously in the regions under study at intervals of 2-3 years. Sh. flexneri dysentery showed morbidity rises occurring at intervals 6-8 years, and their occurrence did not coincide with the periods of elevated morbidity in Sh. sonnei dysentery. The data obtained in the cohort analysis and in the study of recurrent morbidity suggest that Sh. flexneri dysentery produces more pronounced postinfection immunity than Sh. sonnei dysentery, and the immunological factor probably affects the dynamics of the epidemic of these Shigella infections.     

Persistence of genes of epidemical influenza viruses in natural populations in the USSR

Antigenic analogues of all known epidemic human viruses (H1, H2 and H3) have been isolated from natural sources in the USSR. A 5 to 25-year persistence of genes coding haemagglutinins of these viruses in the genome structures of natural populations of viruses have been established. The viruses are more commonly isolated from water birds (ducks, gulls, terns, coots, shelducks, sandpipers), and the circulation of influenza viruses in nature among pigeons, crows, chickens and other birds have been identified. The viruses have been also isolated from bats, whales, squirrels, deer, fishes and lake water. The exchange between the genofond of natural populations of influenza A viruses and epidemic influenza viruses is discussed.     

Epidemiological analysis of acute respiratory diseases (ARD) of viral etiology in the Czech Socialist Republic (CSR] and German Democratic Republic (GDR) over the period 1979 to 1984

An analysis is made of the ARD reported in CSR and the GDR over the period July 1st, 1979 to June 30th, 1984. During that time, there were 27,810,000 cases reported in CSR in the framework of ARD epidemiological surveillance, representing 2.67 cases per one inhabitant, whereas in the GDR, the total number of reported ARD was 28,900,000 yielding 1.73 cases per person. However, the GDR reported higher morbidity per one child of preschool age. The authors believe that the differences in the reported incidence of ARD between the two countries are due to differences in the reporting systems and medical officers' activity during an epidemic and in the interim period. Approximately one third of ARD reported annually in the two countries falls to the period of influenza epidemics. The authors also analyze the etiology of the influenza epidemics which affected the two countries in 1980, 1981, 1982, 1983 and 1984. In most seasons, the causative agents and morbidity excesses were different in the two countries. The drift variant B/USSR/100/83, which caused a major epidemy in CSR in 1984, has not to date been implicated in the DGR in the etiology of ARD. The cyclic epidemic due to Mycoplasma pneumoniae occurred in the GDR already in 1979-80, while CSR experienced it a year later. There was a temporal and territorial correlation between the course of A(H1N1) influenza epidemic in the two countries in 1984.     

Infectious disease mortality in the USSR

In recent decades infectious and parasitic diseases (class 1 according to the International Classification of Diseases-9) constitute 2-3% of causes in the total morbidity structures in the USSR. The main causes of death among diseases of class 1 are tuberculosis (37%), acute enteric infections (30%), septicemia (11%), viral hepatitides (11%), meningococcal infection (4%), measles (2%). The main groups are children aged up to 2 years (48% of fatal cases of diseases belonging to class 1). The territorial irregularity of mortality indices has been revealed.     

Persistence of influenza serum antibodies in humans following immunization with a bivalent A/Victoria and A/New Jersey vaccine.

The persistence of serum antibodies 1 year after immunization with a bivalent vaccine containing recombinant viruses that were antigenically identical with A/Victoria/3/75 (H3N2) and A/New Jersey/8/76 (Hsw1N1) viruses was measured in 128 persons aged 18 to 65 years. Serum samples were tested with the hemagglutination inhibition assay against the two vaccine antigens and against A/Texas/1/77 (H3N2) and A/USSR/90/77 (H1N1) viruses. Prior to vaccination 56% and 79% of the participants had been found to be seronegative to A/Victoria and A/New Jersey antigens respectively; the geometric mean antibody titres were low (1:5 to 1:11) except in persons aged 51 to 65 years, whose mean titre of antibody to the A/New Jersey antigen was 1:23, and persons aged 26 to 35 years, whose mean titre of antibody to the A/USSR antigen was 1:25. By 3 weeks after vaccination 85% of the seronegative persons had a fourfold or greater rise in titres of antibodies to the viruses in the vaccine, and 70% had a fourfold increase in titre of antibody to the A/Texas antigen. Of the persons aged 26 to 35 years (seronegative and seropositive) 68% had a fourfold or greater increase in titre of antibody to the A/USSR antigen. There was no change in the mean titres of 19 unvaccinated control subjects during the observation period. At 6 and 12 months after vaccination the titres of antibodies to the A/Victoria and A/New Jersey antigens had declined moderately in all age groups from those observed 3 weeks after vaccination. The rate of decline was similar for the various antibodies except that to the A/USSR antigen in persons 26 to 35 years of age, in whom the decline was much slower.     

Incidence of antibiotic resistance in Salmonella typhimurium strains isolated in different epidemic situations

A total of 1800 S. typhimurium strains isolated in different regions of the USSR in 1968-1979 were studied. Of these strains, 68.6% were resistant to 6-8 antibiotics, 7.8% were resistant to 2-5 antibiotics, and 23.6% proved to be resistant to all antibiotics. The number of multiresistant strains sharply increased during the last 10 years. The strains isolated from different sources and in different epidemic situations considerably differed in their sensitivity to the action of antibiotics. The infective agents isolated from the hospital foci of salmonellosis were found to possess the maximum multiresistance. The study of the genetic nature of multiresistance showed that the multiresistance strains had a conjugative R-plasmid with resistance determinants CmTc, type Fin+, incompatibility group F1me. The phage typing of the strains with phages from the collection of the Tbilisi Research Institute for Vaccines and Sera revealed that these strains belonged to phagotype 2. The problems of the relationship between the biological properties of causative agents and the character of the epidemic process of the diseases caused by these agents are discussed.     

Allelic polymorphism and site-specific recombination in the opc locus of Neisseria meningitidis

The opc gene is widespread in epidemic and endemic Neisseria meningitidis , but most strains of certain epidemic clones (ET-37 complex, Cluster A4) and a few random endemic isolates lack an opc gene. Four percent of the 1148 bp that contain opc plus the surrounding intergenic region was polymorphic (18 alleles), and many of the alleles contained a 230 bp insertion at a fixed location in the intergenic region. The presence or absence of the insertion reflects site-specific recombination. The alleles are stably inherited within clonal groupings for up to at least 50 years, with rare cases of horizontal genetic exchange. Most statistical methods indicated significant intragenic recombination events within this dataset.     

Prospective means of decreasing suppurative-septic diseases in puerperae and newborn infants

The comparative analysis of the occurrence of purulent septic diseases in mothers during the puerperal period and in newborns, observed in a maternity hospital before and after the introduction of the system of keeping newborns together with their mothers, showed a considerable decrease in the morbidity rate among newborn infants (6 times) and in occurrence of mastitis among puerperae (30 times). This is attributed to a decrease in the frequency of the colonization of newborns and mothers in the puerperal period by the hospital strains of staphylococci belonging to epidemic phagotypes. The gradual elimination of staphylococci of phagotype 80, which dominated for several years, from the hospital was observed. To decrease the morbidity rate, the introduction of the system of keeping newborn infants with their mothers in all maternity hospitals of the USSR is proposed.     

Influenza: viral determinants of the pathogenicity and epidemicity of an invariant disease of variable occurrence

If influenza is a riddle wrapped in mystery inside an enigma, then the viral genes are the riddle, the variable surface antigens for which they code are the mystery, and the course and cause of epidemics the ultimate enigma. Paradoxically, the disease itself has remained a stable and recognizable entity through the years, whether initiated by A/PR/8/34 or A/USSR/90/77 variant viruses. Thus, evolution appears to have preserved the disease but not the virus. Among the questions before us are: (1) Have we become obsessed with differences instead of similarities, and have we overemphasized minor differences in viral (antigenic) structure as epidemic determinants? (2) To what extent do viral antigens reflect selection by population antibody? (3) To what extent is antigenic change the pleiotropic consequence of protein structural alteration for purposes other than escape from specific neutralization? These and other questions are discussed in relating viral form to function.     

The 7th cholera pandemic in the world and the USSR

1,713,057 cases of cholera were registered in the world during the seventh pandemic of the disease at the period of 1961-1989. The pandemic still continues, being the most prolonged pandemic in comparison with earlier ones. During the period of the seventh pandemic 10,723 cases of cholera were registered in the USSR. Great outbreaks occurred in 1965 and 1970-1974. At present sporadic cases of cholera can be registered, and wide circulation of mainly avirulent, nontoxigenic strains of cholera vibrios in environmental objects is characteristic of the epidemic situation.     

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.