Perspectives on influenza surveillance in Europe: European scientific working group on influenza, Brussels.

Although influenza surveillance has reached a high level of sensitivity, it is not given the same priority in all European countries. A recent survey has shown the diversity of the surveillance and diagnostic methods. Suggestions are made to encourage homogenisation of techniques, assistance to less active laboratories, training of personnel, evaluation, and co-operation in the field of animal influenza.

Survey on influenza laboratory diagnostic and surveillance methods in Europe. European Scientific Working Group on Influenza.

The survey was undertaken by ESWI in order to investigate the comparability of the laboratory diagnostic methods and the influenza surveillance systems used in 24 European countries. The results indicate considerable consensus in the general approaches to collection and use of clinical specimens, rapid diagnostic techniques, virus isolation techniques in eggs or/and MDCK cell lines, virus identification and use of inhibition of hemagglutination (IHA) and complement fixation (CF) tests for serological diagnostics. However, the details of the techniques used are somewhat heterogeneous: antigen detection methods (immunofluorescence versus immuno adsorbent assay), isolation methods (eggs versus tissue culture), reagents (locally produced, WHO, commercial) are not always equivalent and results are therefore not really comparable. Some of these discrepancies are due to a lack of resources or a lack of priority for influenza in the country. The greatest differences between individual countries exist in the epidemiological part of surveillance programmes. The mode of collection of influenza related mortality and absentism from work varies considerably in different countries. These findings indicate the need to harmonize viral procedures and surveillance systems in European countries in order to improve validity and comparability of results and as a prerequisite for early information on influenza etiology and spread.

[International cooperation on problems in acute respiratory viral infections]. / Mezinárodní spolupráce v problematice akutních virových respiracních infekcí.

The annual occurrence of acute respiratory infections (ARI) of viral origin incl. influenza, the serious character of influenza epidemics and pandemics were the reason why a network of 110 national influenza centres and four international collaborating centres were created. This worldwide surveillance programme is coordinated by WHO. With advancing integration of Europe scientific groups were created which implement this programme in Europe. EUROSENTINEL analyzes the notified morbidity from influenza and ARI in eight participating countries, EUROGEIG concentrates on the programme of influenza prevention and the preparation of anti-pandemic provisions, EUROGROG associates 27 National influenza centres which in the course of the season exchange information on the incidence of influenza and other respiratory viruses. ESWI (European Scientific Working Group on Influenza) organizes clinical and epidemiological investigations on the influence of influenza infection and the impact of anti-flu vaccination; it tries to harmonize the surveillance programme and raise its standard and strives for joint research projects. The National reference laboratory in Prague participates in all these programmes and takes also active part in some projects.

[The antigenic characteristics of influenza A viral strains circulating synchronously in 2 separated areas (the CzSFR--Saint Petersburg)]. / Antigennaia kharakteristika shtammov virusa grippa A, tsirkulirovavshikh sinkhronno na dvukh otdalennykh territoriiakh (ChSFR--Sankt-Peterburg).

A comparative study of the antigenic characteristics of influenza A (H1N1) and A (H3N2) virus strains isolated during the same epidemic season, 1989-1990, in St. Petersburg and CzSFR was carried out by routine serological methods and by cross-challenge of immunized mice. Antigenic differences were found only among serosubtype A (H1N1) strains isolated in different areas. The study was carried out in connection with potential occurrence of influenza epidemic outbreaks from local sources.

[Clinical diagnosis and laboratory study of acute respiratory diseases of viral origin in children]. / Klinická diagnóza a laboratorní vysetrení akutních respiracních onemocnení virového puvodu u detí.

The authors analyzed retrospectively a group of 477 children aged two months to 16 years (mean age 6 years and 5 months), hospitalized on account of acute respiratory disease and subjected to virological examination. The aetiology was revealed in 53% of the sick children. In the elucidation of the aetiology participated a number of respiratory viruses, in particular the respiratory syncytial virus. The clinical picture of the disease was very varied. It was confirmed that the clinical picture does not make it possible to express in a considerable proportion of patients suspicion of an actual infectious aetiology. A mixed aetiology of acute respiratory diseases and a varied clinical picture indicate the necessity of a rapid virological and bacteriological examination in hospital practice.

[An epidemic of type B influenza in the geriatric psychiatry department of a psychiatric hospital]. / Epidemie chripky typu B na gerontopsychiatrickém oddelení psychiatrické lécebny.

The authors submit an epidemiological and aetiological analysis of a local epidemic of influenza type B which occurred in April 1989 in a mental hospital at the geronto-psychiatric department. In the course of two weeks 26 patients and 5 health workers from a total of 72 exposed subjects contracted influenza. 50% of the patients who contracted influenza died. The authors emphasize the necessity of early preventive epidemiological provisions in institutions of this type.

Influenza virus detection in clinical specimens.

The authors compared the results of influenza A (H1N1) and influenza A (H3N2) virus detection in nasopharyngeal swabs from flu patients by molecular hybridization (MH), ELISA, virus isolation and seroconversion. Using the immunofluorescence (IF) technique influenza virus was detected in cell suspensions from the first chick embryo passage. Altogether 63 swabs from various epidemic seasons were separated into 3 groups according to specimen sampling and storage. It was shown that influenza virus RNA could be found in 16 out of 22 swab specimens (72%) stored at -70 degrees C without thawing and that ELISA revealed the influenza virus antigen in 19 cases (86%); in contrast, IF was positive in 6 (27%) and virus isolation in 5 (22%) cases only. However, the positive rate of MH decreased to 9% in 21 swab specimens repeatedly thawed and stored at -20 degrees C and was completely negative after prolonged storage of repeatedly thawed samples. Despite these conditions, ELISA was still successful in both latter sample groups (71-80%). For specificity control, 29 samples coming from patients with influenza B virus and other respiratory virus diseases (adeno- and respiratory syncytial virus) were used.

[Surveillance of acute respiratory diseases in the 1988/1989 season in Czechoslovakia]. / Surveillance akutních respiracních onemocnení v sezóne 1988/1989 v CSSR.

The authors submit an analysis of results of surveillance of acute respiratory diseases during the 1988/1989 season in the CSSR. The influenza epidemic took place between the 4th and 11th calendar week with a peak in the 7th week. During the epidemic 19.7% of the population in the CSR contracted the disease. The influenza epidemic was preceded by a high incidence of infections caused by a respiratory syncytia virus. As to the aetiology, influenza viruses subtypes A/H1N1/, A/H3N2/ and type B participated practically equally in the epidemic. The authors discuss the observed changes in the influenza epidemiology in recent years in Czechoslovakia and neighbouring countries.

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.

Epidemiological analysis of acute respiratory disease (ARD) and characteristics of the influenza epidemic in Bohemia during the season 1986/1987.

The authors analyze the findings of epidemiological and virological surveillance of ARD in Bohemia during the season 1986/1987. In all, 57.5% of the Czech population was affected by acute respiratory disease (ARD). There were 5,950,832 cases reported, 124,444 complications (2.1% of the overall morbidity rate) and 5,374 deaths due to influenza, bronchitis, pneumonia and chronic pulmonary affection. The influenza epidemic commenced during the 48-th calendary week (CW) and lasted 5 weeks till the 52-nd CW. The epidemic was due to an influenza virus strain of the subtype A(H1N1) antigenically related to the drift variant A (Singapore) 6/86. Within an extremely short period of the epidemic, 1,094,865 influenza cases were reported and 22,313 cases of complications. 10.7% of the CSR population were affected during the epidemic in whose etiology noninfluenza respiratory viruses were significantly implicated, especially adenoviruses (41.7%) and the RS virus (26.9%). There was no excessive mortality in the course of the epidemic. The authors discuss the atypical nature of this particular influenza epidemic and the etiological role of respiratory viruses.

Do influenza epidemics spread to neighbouring countries?

This study compares the main causes of influenza epidemics reported in Czechoslovakia (CSR) and the German Democratic Republic (GDR) during the 9 seasons between 1980 and 1988. The influenza epidemics due to identical virus types were experienced in the two countries in the 1980, 1984 and 1986 seasons, and of these only the 1984 epidemic associated with A-strain influenza A/Chile/1/83 (H1N1) virus could be demonstrated to spread from the eastern parts of the CSR to the northern areas of the GDR. This implies that influenza epidemics due to identical drift variants spread only exceptionally from one country to the other during the period of observation, in spite of a busy tourist activity across the borderline.

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.

Prospective study of pharyngitis: clinical diagnosis and microbiological profile.

A prospective study of pharyngitis was carried out in the general population of twenty-two thousand in a small country town, over a period of ten weeks in the fall of 1984. It has been confirmed that, as in the past clinical diagnosis "streptococcal" and "nonstreptococcal" pharyngitis without microbiological examination is still highly inaccurate. From the clinical and microbiological parameters, the incidence in the period of follow-up was calculated as 7.2 and 12.0 cases per 100 population per year for streptococcal and nonstreptococcal pharyngitis, respectively. These data document the health importance of this disease which is frequently underestimated. The M (by M or OF antigens) typability accounted for 62% of group A strains isolated, the prevailing types being M 1 and M 12. Comparison of M and OF typability of field strains immediately after isolation and three weeks later proved the superiority of an early typing. The accurate identification of prevailing types is essential for the prospect of streptococcal vaccine. In streptococcal pharyngitis cases treated with penicillin, the increase of antistreptolysin O and antideoxyribonuclease B titres was recorded in very few instances during a three week period after the onset of the disease. The examination of patients with nonstreptococcal pharyngitis aimed at detecting the role of some viruses or of M. pneumoniae proved that the etiology by these agents was practically nil in the cases concerned at this particular period of time. This finding suggests focusing interest on a possible role of other pathogens. The morbidity rates of pharyngitis, and the clinical as well as the microbiological data resulting from the study make it urgent to pay further attention to this infection and to attempt to elucidate the missing points in the etiology and diagnosis of this disease which belongs to the bacterial infections most frequently seen in man in economically developed countries.

[Conservativism of the matrix protein of paramyxoviruses]. / Konservatizm matriksnogo belka paramiksovirusov.

Cross reactions among paramyxoviruses were determined by the immunoblot method. Human parainfluenza viruses, types 1-3, avian parainfluenza virus type 4, mumps, Sendai, and measles viruses were used. Antisera to human parainfluenza viruses were shown to cross-interact with proteins NP and M of other types, and all antisera to the members of Paramyxovirus genus cross-reacted with M proteins of other paramyxoviruses. No cross reactions with measles virus proteins were observed. It is concluded that M protein is the most conservative protein of paramyxoviruses.

[A comparative analysis of epidemic strains of the influenza A virus (H1N1), isolated in the USSR and Czechoslovakia in 1986]. / Sravnitel'nyi analiz épidemicheskikh shtammov virusa grippa A (H1N1)izolirovannykh v SSSR i ChSSR v 1986 g.

A comparative study of antigenic and molecular-biological properties of epidemic influenza virus strains isolated in the USSR and CSSR in the autumn-winter, 1986-1987 was carried out and showed that the epidemics in both countries were due to influenza A viruses of H1N1 subtype, antigenically related to the reference A/Taiwan/1/86 and A/Singapore/6/86 strains, which was confirmed by electrophoretic studies. The strains were found to vary in sensitivity to heating and to the inhibitors.

Occurrence and aetiology of acute respiratory diseases: results of a longterm surveillance programme.

Totals of 58,661,000 acute respiratory disease (ARD) cases, 1,376,651 bronchitis and pneumonia complications, and 93,042 deaths from influenza, bronchitis, pneumonia or chronic pulmonary affection were notified during 11 years of ARD surveillance from 1975 to 1986. All ARD seasons started with the first phase in September-December; this increase in morbidity was caused chiefly by adenoviruses, parainfluenza viruses, rhinoviruses and M. pneumoniae. Second wave of ARD morbidity occurring in January-April used to be explosive and was associated with an influenza epidemic in 9 of the 11 seasons; only in 1978/79 and 1984/85 the ARD epidemics were caused by adenoviruses and especially RSV, the share of influenza being minimal. Pneumonia and bronchitis excesses occured during epidemics caused by M. pneumoniae in 1975/76, 1980/81 and 1985/86. Particularly high mortality excesses occurred in 1976, 1977 and 1983 during epidemics elicited by a new drift variants of influenza A(H3N2). Identification of viral agent of M. pneumoniae attempted in 5474 ARD cases was successful at 37.4%. The respective contributions of parainfluenza viruses, adenoviruses, influenza A virus and RSV to overall aetiologically identified morbidity were 14.2, 13.9, 13.8, and 12.0%. Mixed infections (2-3 agents identified simultaneously) accounted for 14.6% of cases. Type B influenza virus, rhinoviruses, enteroviruses and herpes simplex virus contributed only by 5.6-7.8%. In ordinary seasons the share of M. pneumoniae in aetiologically identified ARD morbidity was 0.6-3.8%; this agent displayed predominance at 5-year cycles, when accounting for 20.5-38.9% of cases. The most frequently detected agents in individual age groups were as follows: in preschool children parainfluenza (18.6%), RSV (16.6%), and adenoviruses (17.4%); in school children M. pneumoniae (26%), influenza A and B (10.2 and 14.7% respectively), and adenoviruses (10.7%); in adolescents and young adults influenza type A (20.2%), M. pneumoniae (15.0%), and rhinoviruses (13.3%); in adults above 25 years age influenza A virus (38%), and other respiratory viruses at a frequency lower than 10% each.

[Specific and nonspecific indicators of activation of influenza viruses before an epidemic caused by influenza viruses subtype A/H3N2 and type B in Czechoslovakia in 1986]. / Specifické a nespecifické indikátory aktivizace chripkových viru pred epidemií vyvolané viry chripky subtypu A/H3N2/ a typu B v CSR v roce 1986.

The authors submit an aetiological and epidemiological analysis of the influenza epidemic which occurred in the CSR between the 4th and 14th week of 1986 and was caused by the influenza virus subtype A/H3N2/ and type B. The epidemic affected a total of 27.1% of the population, in the age group of 0-5 years 63.7%, in the age group 6-14 years 52.7% and in the age group above 15 years 17.1%. In the course of the epidemic 77,458 cases of pneumonia and bronchitis were reported and 1,412 deaths with the diagnosis influenza, bronchitis, pneumonia and chronic affection of the lungs. The authors analyze also specific indicators of the activation of influenza viruses and reach the conclusion that serological evidence of the circulation of influenza viruses in the population was detected already in the third quarter of 1985, the first isolations were made six weeks before the influenza epidemic. Activation of the influenza viruses is indicated already during the pre-epidemic period by some non-specific indicators which include the rising number of patients with acute respiratory affections in surgeries and the rising number of children absent from nurseries and nursery schools on account of these diseases. The most sensitive non-specific indicator is the rising number of patients with respiratory diseases in surgeries of the First aid medical service.

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.