Mixed infections with influenza A and B viruses.

In the course of an influenza A and B epidemic, influenza virus was isolated from 46 patients. Seven of these patients showed seroconversion against influenza virus plus another respiratory virus. In 9 patients, simultaneous antibody increase against both influenza A and B viruses was demonstrated, but only a single virus type was isolated. In one case the isolated virus population could be separated into type A and B viruses.

Antibodies to new variants of subtype A(H3 N2) influenza virus in pigs.

Following an explosive epidemic of A(H3N2) influenza among the human population of Czechoslovakia in 1983, haemagglutination-inhibiting antibodies (titre range 10-640) against strains A/Texas/77, A/Bangkok/79 and A/Philipines 2/83 were detected in 93% of sera collected from 135 pigs on three farms. Only 6.6% of sera were negative. Anti-neuraminidase antibodies were detected at rates of 81% and 23% in two and one of the herds, respectively. Antibodies against A/RNP were demonstrated by the immunodiffusion test in only one of the herds in 10 out of 45 sera tested. This herd was also found to possess antibodies against both envelope antigens of a human A(H1N1) subtype strain. Haemagglutination-inhibition tests with strains A/Hong Kong/68 (H3 N2), A/sw/Shope 15/31, A/sw/Bavaria 2/77 and A/New Jersey 8/76 (H1 N1) were negative in the sera from all three herds.

Isolation of an influenza A virus strain from a bird embryo (Larus ridibundus) collected in Slovakia.

Avian influenza virus A/Larus 36/77 (Hav7Nav1) was isolated in 1977 from a trinket (Larus ridibundus) embryo. This result suggests the possibility of vertical transmission of influenza A virus.

Type A influenza virus strains isolated from free living ducks in Czechoslovakia during 1978-1981.

Eight influenza virus A strains were isolated from 269 cloacal swabs taken from wild ducks (Anas platyrhynchos), shot during their autumn migrations in the years 1978-1981. One strain was identified as subtype A-H3N8N6 (Hav7Neq2Nav1), the remaining seven as subtype A-H4N6 (Hav4Nav1).

Isolation of influenza virus from wild ducks (Anas platyrhynchos).

In the course of studies on influenza virus ecology, Influenzavirus A was isolated from a cloacal smear from a wild duck (Anas platyrhynchos) caught in west Slovakia. The strain was identified as A(Hav7Nav1). The results of virus isolation experiments from other species of aquatic and other small birds were negative.

Further evidence of the circulation of PMV-4 and influenza viruses with N2-1957 enzyme in the migratory waterfowls.

In the years 1980-1984, one paramyxovirus type 4 and 11 influenza viruses were isolated from cloacal swabs collected from migratory waterfowls in Fed. Rep. Germany. One influenza virus of H4N8 subtype was isolated from swabs of commercial ducks collected at an abbatoir. Seven of 10 influenza strains, isolated from mallard ducks and coot were identified as a mixture of 2-3 strains of H1, H4, and H5 subtype; 3 virus strains from the same locality relate antigenically to subtype H4 with enzyme serologically identical with N2--Singapore/57 as demonstrated by means of polyclonal and monoclonal antibody.

Vaccination of an adolescent group with A (H3N2) + A(HSW1N1) bivaccine before an A (H1N1) influenza epidemic.

A group of 35 adolescents aged 18--22 years were vaccinated intradermally with 0.2 ml of a mixed A (H3N2) + A (Hsw1N1) formolized vaccine and revaccinated with A (Hsw1N1) monovaccine 10 days before an A (H1N1) influenza epidemic. The vaccination had no effect on morbidity or the clinical course of disease. Serology revealed a primary immune response to A (Hsw1N1) and a booster response to A (H3N2). Apparently, prevention of a new influenza subtype by formolized vaccine possessing only the corresponding neuraminidase type is ineffective.

A further member of the Yucaipa group isolated from the common wren (Troglodytes troglodytes).

In 1977, 477 small birds of 52 species were virologically examined. Five cloacal swabs from Troglodytes troglodytes yielded two paramyxovirus strains which were found antigenically related to, but not identical with Ch/Yucaipa/California/56 virus according to three serological tests. The ecological significance of these findings and the possibility of paramyxovirus classification into four types are discussed.

Incidence of paramyxoviruses in free-living birds in 1978-1982.

Together 41 paramyxovirus (PMV) strains (25 PMV-1, 10 PMV-4, and 6 PMV-6 serotypes) were isolated from cloacal swabs of 910 free-living birds trapped in West Slovakia from 1978 to 1982. The PMV strains were found in 9, mostly aquatic bird species. Strains belonging to the PMV-1 serotype were isolated yearly, indicating its wide distribution and circulation in nature. The strains of PMV-4 and PMV-6 serotypes found only in 1978-1980, represented the first isolations in Europe. Antigenic analysis by haemagglutination-inhibition (HI), neuraminidase-inhibition (NI), complement-fixation (CF), and gel double diffusion (DD) tests proved the relatedness of the surface antigens of newly isolated PMV strains with those of PMV-4/ Duck Hong Kong D3/75 and PMV-6/Duck/Hong Kong 311/80 strains. One-way reaction between PMV-4 serotype and mumps virus was demonstrated using hyperimmune rat sera. Electron microscopic observation of isolated virus strains revealed structures typical of PMV.

Persistence in nature of influenza virus A/eq/Praha/56 (Heq1Neq1).

Equine influenza occurred in Czechoslovakia 14 years after the last epizootic in horses that had returned from abroad. Six strains A (Heq1Neq1) antigenically related to, but not identical with, strain A/eq/Praha/56 were isolated from 10 washings. Seroconversion was demonstrated with paired sera, but the antibody increase was more marked against the newly isolated strain.

The source of avian paramyxoviruses isolated during an outbreak of influenza among children.

In 1986 five avian paramyxovirus (PMV) strains were isolated in embryonated chicken eggs from sick children with influenza. The strains were identified as PMV-2 serotype due to the close antigenic relationships between their HN-proteins and of the reference PMV-2 strains isolated from different birds all over the world. No seroconversion to the isolates was found in the sick children, however, HI-antibodies were detected in hen's sera, eggs of which were used for the new strains isolation. The possible origin of isolated PMV-2 viruses is discussed.

Levels of immunoglobulins and antibodies to haemaglutinin and neuraminidase of influenza virus in nasal secretions after natural infection.

Nasal washings (NW) from 16 influenza patients in the course of an epidemic in November and December, 1974 were examined for the presence of influenza virus, immunoglobulins (Ig) and titres of haemagglutination inhibiting (HI) and neuraminidase inhibiting (NI) antibodies. Influenza virus identical with A/Port Chalmers/1/73 (H3N2), increased levels of IgA and occasionally IgG, and specific antibodies were detected in the NW. The dynamics of HI and NI antibody formation did not differ substantially, but there were individual differences in titres and persistence of antibodies. Convalescent sera always contained increased levels of HI and NI antibodies. In some cases, the titres of antibody to viral ribonucleoprotein did not increase.

[The antigenic and biological properties of influenza A (H1N1) viruses isolated in the USSR and the Czechoslovak Federal Republic in 1988-1989]. / Izuchenie antigennykh i biologicheskikh svoistv virusov grippa A (h1N1), izolirovannykh v SSSR i ChSFR v 1988--1989 gg.

A comparative study of influenza A (H1N1) virus strains isolated in one epidemic season (1988-1989) in neighbouring countries was carried out. Using polyclonal and monoclonal antibodies, some of the isolates were shown to have different antigenic and biological properties which probably determined the different intensity of the epidemic situation in the USSR and CzSFR in 1988-1989.

Characterization of envelope antigens of influenza A (H3N2) virus isolated during 1983-1985 epidemics and from sporadic cases of infection.

Ten strains of influenza A (H3N2) virus isolated from an outbreak in 1983, and ten strains isolated in 1985 from sporadic cases of infection were included in the study. For characterization of envelope antigens were used the polyclonal and monoclonal antibodies tested in the reaction of haemagglutinin inhibition, neuraminidase inhibition, and by lectin test. The strains but slightly different in the tests with polyclonal antibodies could clearly be classified to 3-4 groups using 5 monoclonal antibodies to H antigen of A/Bangkok 1/79 and A/Philippines 2/82 strains. Strains from the 1983 epidemics represent a more homogeneous group of which only one of ten strains failed to react with monoclonals of the strains A/Bangkok and A/Philippines. Strains from sporadic cases of infection in 1985, except for two strains, did not react at all with the monoclonal discriminating A/Bangkok and A/Philippines. The other strains could be classified to three groups, i.e. whether they agreed with 4, 2 or none of the A/Philippines H antigen epitopes. Alterations of neuraminidase are less apparent, and cannot be defined by means of normal immune sera. With the use of monoclonal antibodies the strains under study do not react any more with the strains of 1968-1973 influenza virus; yet the monoclonals to A/Texas/77 strain still do recognize one or two epitopes of the 1983-1985 strains.

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.

A study on the role of birds in the spread of infections.

During three expeditions undertaken in March 1977 to June 1978, 797 cloacal swabs were collected from birds of 54 species. Seven salmonella strains of six serotype were isolated from Larus ridibundus (five strains), Corvus frugilegus and Acrocephalus schoenobaenus (one each). Four strains of influenza A (HAV2 NA4V) virus were isolated from Larus ridibundus. For the first time in Czechoslovakia, two strains of Yucaipa paramyxovirus were isolated, both of them from Troglodytes troglodytes. These results are the first contribution to a study on the role of birds as hosts and vectors of different bacterial and viral agents.

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.