Etiology of mild acute infectious myocarditis. Relation to clinical features

The etiology of mild myocarditis, diagnosed on the basis of serial ECG changes during an acute infection, was studied in 126 consecutive conscripts. A fourfold rise in the antibody titers in the paired serum samples was required for a positive etiologic diagnosis. An etiologic diagnosis was made probable in 47% of the patients. Adenovirus was incriminated in 19 patients, vaccinia in 12, influenza A in eight, beta-hemolytic Streptococcus in six, mononucleosis in five and Mycoplasma in three. Chlamydia, influenza B and Coxsackie B4 were each found in two patients; parainfluenza, mumps and adult Still's disease were each found in one patient. The incidence of vaccinia myocarditis was 1/10000 smallpox vaccinations. Clear-cut myopericarditis was usually noted during vaccinia, mononucleosis, Mycoplasma, Chlamydia and Coxsackie B4 infections. Adenovirus and influenza A myocarditis was most often subclinical, being mostly detected only because of ECG screening of patients without cardiac symptoms. Frequent recent ventricular extrasystoles were most often triggered by a beta-hemolytic Streptococcus infection. The etiology of infectious myocarditis seems to reflect the overall profile of viruses and other infective agents in the study population at that particular time. Cardiotrophic viruses such as Coxsackie B only rarely cause myocarditis outside epidemics.

Reappearance of influenza B/Victoria/2/87-lineage viruses: epidemic activity, genetic diversity and vaccination efficacy in the Finnish Defence Forces

A new B/Shangdong/7/97-like influenza virus (Victoria/2/87 lineage) predominated during the 2002/2003 epidemic season in Finland and was estimated to account for 2246 of the 13,496 feverish upper respiratory tract infections (URIs) occurring among conscripts in the Finnish army. The incidence (1716/10,000 conscripts) was indicative of moderate epidemic activity at most. Analysis of the cross-reactive antibodies induced in 1988 suggests that the basis of the protection was probably established during the childhood of the conscripts. Vaccination in autumn 2002 prevented 42% of the URIs during the influenza B outbreak and 71% (95% CI 42-85) of infections interpreted as influenza B. Despite the low genetic variability of the Shangdong/7/97-like viruses, breakages of a potential glycosylation site in haemagglutinin (HA1, position 197) were frequent; their biological significance is discussed. The Shangdong/7/97-like strains were HA1/NA reassortants, as were also the less abundant strains that for HA1 belonged to the B/Yamagata/16/88 lineage. A further reassortment, which probably emerged during the outbreak in one of the garrisons, supports our hypothesis that circumstances in these settings may especially favour the emergence of diversity by reassortment.

Enterovirus, mycoplasma and other infections as predictors for myocardial infarction

OBJECTIVES

To study antibodies against five infectious agents for their prediction of major coronary events in men with and without evidence of coronary heart disease at baseline.

DESIGN

A case-control study nested within a prospective population study.

SUBJECTS

The study cases included 441 men 45-64 years old with nonfatal myocardial infarction or coronary death within a mean follow-up time of 10 years. A total of 165 men had already signs of heart disease at baseline, whilst 276 were apparently healthy at the beginning of the study. Two controls for each case were matched for age, heart disease status and place of residence. Antibodies against enterovirus, Mycoplasma pneumoniae, Chlamydia pneumoniae, cytomegalovirus and adenovirus were determined.

RESULTS

Men without reported baseline heart disease, but not those with heart disease, showing the highest quartile of antibodies to enterovirus and mycoplasma or increased levels of immune complex-bound antibodies to chlamydia had a significantly higher risk of coronary events than men with lower level of antibodies. The increased risk demonstrated in men with high levels of antibodies to enterovirus and mycoplasma remained significant after adjustment for other antibodies, acute-phase reactant and conventional risk factors. Serological evidence of infection by multiple agents was also significantly associated with coronary events.

CONCLUSIONS

Serological evidence for several infectious agents is associated with the risk of coronary heart disease, but only in men without baseline history of heart disease.

Virological and serological analysis of rhinovirus infections during the first two years of life in a cohort of children

The occurrence of rhinovirus infections in a cohort of 329 children during the first 2 years of life was determined by virus detection and serological methods. Rhinovirus detection on nasopharyngeal aspirates and middle ear fluids comprised a combination of virus isolation in HeLa Ohio cells and a reverse transcription-polymerase chain reaction (RT-PCR)-hybridization assay on the inoculated cell cultures. Nasopharyngeal aspirates were collected when the child was referred to the study clinic because of respiratory symptoms. Nasopharyngeal aspirates and middle ear fluids were collected after clinical diagnosis of an acute otitis media. Complement-fixing antibodies to rhinovirus were determined from scheduled serum specimens collected at 6, 12, 18, and 24 months of age and from paired sera taken in the cases of acute otitis media. Rhinovirus infections were shown to be common in infants, 24% of the children had complement-fixing antibodies at the age of 6 months and 22% had had at least one rhinovirus episode indicated by virus detection. At the age of 2 years, 91.3% of the children had rhinovirus-specific antibodies, while 79% of the children had experienced rhinovirus infection as judged by the virus detection tests. However, the complement-fixation assay was poor as a diagnostic test. Of 458 acute otitis media episodes studied, 41% were shown to be associated with a rhinovirus by RT-PCR-hybridization, while significant fourfold rise in rhinoviral antibodies was detected only in 7% of the cases.

Epidemiology of documented viral respiratory infections and acute otitis media in a cohort of children followed from two to twenty-four months of age

BACKGROUND

Viral upper respiratory infections (URIs) are considered major risk factors for acute otitis media (AOM) in young children. We studied the epidemiology and relative roles of different viruses in respiratory infections in a cohort of 329 Finnish children followed from 2 months to 2 years of age.

METHODS

A nasopharyngeal aspirate (NPA) was collected whenever the child had signs and/or symptoms of URI and tested for the presence of common respiratory virus antigens or infectivity/nucleic acid (only rhinoviruses). Possible repeated detections of a given virus during a 30-day period were considered to represent a single designated virus-specific episode. AOM and URI episodes were defined in a similar way.

RESULTS

At least one virus was detected in 837 (41.7%) of the 2005 NPA specimens examined. Rates of URI and virus-specific episodes showed expected seasonal variation with major peak occurrences coinciding with or preceding those of AOM. The proportions of rhinoviruses, respiratory syncytial (RS) virus, parainfluenza virus (PIV) type 3, influenza virus A and adenoviruses were 63.1, 14.7, 6.7, 6.7 and 6.2% of the total of 761 virus-specific episodes. Influenza virus B, PIV1 and PIV2 were each responsible for approximately 1% of the episodes. AOM was diagnosed in 870 URI cases (43.4%) and in 43.3% of cases associated with a virus-positive NPA. The latter figure was clearly higher (57.7%) for RS virus-positive specimens.

CONCLUSIONS

The seasonal coincidence of URI and AOM demonstrated the obvious role of URI in the pathogenesis of AOM. The occurrence of rhinoviruses and RS virus in URI was strikingly more common than that of any other virus tested. Although rhinoviruses were definitely the most frequently found viruses in NPA specimens, the association of RS virus with concurrent AOM was relatively higher than that of any other virus.

Acceptable protective efficacy of influenza vaccination in young military conscripts under circumstances of incomplete antigenic and genetic match

Commercial inactivated parenteral influenza vaccines reduced febrile (> or = 38 degrees C) respiratory illness by 53% (95% CL: 41-63%) during a 3 week outbreak in 1998 when A/Sydney/5/97(H3N2)-like influenza viruses were shown to be the predominant etiological agents and an older antigenic variant, A/Nanchang/933/95, served as the vaccine virus. The calculatory efficacy for preventing virologically diagnosed influenza infections was 57% (95% CL: 40-68%). The study population consisted of 1374 young male military conscripts. Vaccination coverage on a voluntary basis was 67%. Vaccination was ineffective in preventing febrile illness during a second epidemic wave lasting 2 weeks when mainly adenoviruses were shown to have been circulating in the garrison. Out of the 36 nasopharyngeal aspirates positive for influenza A by antigen detection, 18 A/Sydney/5/97-like strains (10 from non-vaccinated and eight from vaccinated subjects) and two A/Nanchang/933/95-like strains (both from non-vaccinated subjects) were isolated in MDCK cell cultures. Intraepidemic variation was detected among the A/Sydney/5/97-like field strains in their HA1 sequences and reactivity in HI tests, but no evidence was obtained that this variation would have been of significance to the virus in breaking through the vaccination-induced immunity.

Microbial etiology of community-acquired pneumonia in the adult population of 4 municipalities in eastern Finland

To determine the etiology of community-acquired pneumonia in the adult population of a defined area, specific antibody responses in paired serum samples, levels of circulating pneumococcal immune complexes in serum samples, and pneumococcal antigen in urine were measured. Samples (304 paired serum samples and 300 acute urine samples) were obtained from 345 patients > or =15 years old with community-acquired, radiologically confirmed pneumonia, which comprised all cases in the population of 4 municipalities in eastern Finland during 1 year. Specific infecting organisms were identified in 183 patients (including 49 with mixed infection), as follows: Streptococcus pneumoniae, 125 patients; Haemophilus influenzae, 12; Moraxella catarrhalis, 8; chlamydiae, 37 (of which, Chlamydia pneumoniae, 30); Mycoplasma pneumoniae, 30; and virus species, 27. The proportion of patients with pneumococcal infections increased and of those with Mycoplasma infections decreased with age, but for each age group, the etiologic profile was similar among inpatients and among outpatients. S. pneumoniae was the most important etiologic agent. The annual incidence of pneumococcal pneumonia per 1000 inhabitants aged > or =60 years was 8.0.

Improved sensitivity and specificity of enzyme immunoassays with P1-adhesin enriched antigen to detect acute Mycoplasma pneumoniae infection

An in-house P1-enriched (168-kDA protein) Mycoplasma pneumoniae antigen preparation was compared in IgG, IgA and IgM enzyme immunoassays (EIAs) to the respective EIAs employing crude antigen lysate, antigen prepared by Triton X-114 partition and two commercial antigens, one of which was an ether-extracted antigen and the other a P1-enriched antigen. In addition, three commercial kits from Sanofi Pasteur, Novum Diagnostica and Savyon Diagnostics were also assessed for comparison. Diagnostic sensitivity was studied with paired samples from adults (n=37) with acute respiratory illness interpreted as acute, recent or past infection to M. pneumoniae on the basis of the results of complement fixation test (CFT). If the consensus of at least two methods is taken as the true positive for acute infection, the diagnostic sensitivities of combined IgG and IgM EIAs were 100% for the Platelia(R), Sero MP and in-house EIAs whereas for the Novum EIAs and CFT- 97% and 74%, respectively. Moreover, the sensitivity of the P1-enriched antigen was proven superior on the basis of systematically highest OD(405 nm) ratios between convalescent and acute serum samples. Analytical specificity was studied by screening serum samples from 92 Finnish blood donors and 111 serum samples from cord blood. Diagnostic specificity was studied in a blind testing of 30 paired serum samples from infants with pneumonia of variable etiology. No single misinterpretation of acute infection from the group of samples with other respiratory diseases did occur. The present study confirmed and extended the earlier observations of the usefulness of P1-enriched antigen for reliable serologic diagnosis of acute M. pneumoniae infection.

Chlamydia pneumoniae is an important cause of community-acquired pneumonia in school-aged children: serological results of a prospective, population-based study

The aetiology of community-acquired pneumonia in childhood was studied in the total population of 8851 children in the area of 4 municipalities in eastern Finland. All cases of community-acquired pneumonia (n = 201) were registered during a surveillance period of 12 months between September 1, 1981 and August 31, 1982. The diagnosis of pneumonia was verified radiologically in all identified cases. The diagnosis of chlamydial infection was based on an antibody response measured by complement fixation (CF), by enzyme immunoassay (EIA; IgG or IgM) or by microimmunofluorescence (MIF; IgG or IgM), and the diagnosis of mycoplasmal infection on CF alone. In total, 29 cases of Chlamydia sp. infection were diagnosed; 20 were caused by Chlamydia pneumoniae. Thus, C. pneumoniae was an aetiological agent in 10%, of the 201 pneumonia cases: the proportion was 9% for children aged 5-9 y and 31% for those aged 10 y or more. In the study population, the total incidence of C. pneumoniae pneumonia was 2.3/1000/y. Mycoplasma pneumoniae serology (CF) was positive in 44 patients (22%); the total incidence of M. pneumoniae pneumonia was 5.0/1000/y. Serological evidence of both Chlamydiae and M. pneumoniae was detected in 9 (41%) patients. Our results indicate that C. pneumoniae is an important cause of community-acquired pneumonia in school-aged children. Diagnostic serological response to Chlamydia species or M. pneumoniae was found in 42% of pneumonia patients between 5 and 9 y of age and in 67% of patients aged 10 y or more. Thus, we suggest that macrolides should be considered as an empirical antimicrobial treatment for community-acquired pneumonia, especially in school-aged outpatients.

Efficacy of PCR and other diagnostic methods for the detection of respiratory adenoviral infections

Five methods were evaluated for the detection of adenovirus directly from nasopharyngeal aspirates (NPA), including conventional and rapid virus culture, two antigen detection tests, and the polymerase chain reaction (PCR). NPA specimens were obtained from 269 military conscripts suffering from an acute respiratory infection during an adenovirus outbreak. In 133 cases, paired blood specimens were also available. Virus culture followed by a hexon-specific immunofluorescence revealed 159 (59%) adenovirus-positive specimens and it was used as a reference method. In comparison to conventional culture, a rapid 2-day culture method had a sensitivity of 71%. The sensitivities of an enzyme immunoassay and time-resolved fluoroimmunoassay were 53% and 46%, respectively. The PCR method employing Ad7 hexon-specific primers showed a high sensitivity of 94%, and revealed an additional 15 (6%) specimens that could not be confirmed by virus culture. Serology based on significant adenovirus antibody rises had a diagnostic efficacy nearly equal to the virus culture and PCR methods, but a relatively high number of discordant results was found. The present study demonstrates that PCR is a very sensitive rapid diagnostic method for detecting adenovirus specific DNA in NPA specimens of adults.

Etiology of childhood pneumonia: serologic results of a prospective, population-based study

BACKGROUND

To investigate the etiology of pediatric community-acquired pneumonia, we conducted a prospective, population-based study covering the total population <15 years of age (n = 8851) in 4 municipalities in eastern Finland.

MATERIALS AND METHODS

The number of patients was 201; chest radiographs were available for all cases and paired sera for serologic assays were available for >90% of cases. The methods included assays for antibody response to 3 pneumococcal antigens, specific pneumococcal immune complex assays and conventional antibody tests for mycoplasmal, chlamydial and viral infections.

RESULTS

Serologic evidence of specific microbial etiology was obtained in 133 (66%) of the pneumonia patients. Bacterial infection was diagnosed in 102 cases (51%) and viral infection in 51 cases (25%). Streptococcus pneumoniae was the most common agent (57 cases; 28%), followed by Mycoplasma pneumoniae (44; 22%), respiratory syncytial virus (43; 21%) and Chlamydia spp. (29; 14%). Haemophilus influenzae was identified in only 6% and Moraxella catarrhalis in only 3% of the children. More than one specific infection was found in 51 patients (25%). The proportion of pneumococcal cases varied from 24 to 36% by age. Mycoplasma infections were seen mostly in patients > or =5 years and Chlamydia infections in patients > or =10 years of age.

CONCLUSIONS

The results of our prospective, strictly population-based study confirm the importance of S. pneumoniae in the etiology of community-acquired pneumonia in children of all ages. M. pneumoniae and Chlamydia pneumoniae are important from the age of 5 years onwards.

Nasopharyngeal eosinophil cationic protein in bronchiolitis: relation to viral findings and subsequent wheezing

A prospective 4-month follow-up of children hospitalized with bronchiolitis revealed that high concentrations of eosinophil cationic protein (ECP) in nasopharyngeal aspirates (NPA) are predictive of wheezing after bronchiolitis. In the 29 patients who received no anti-inflammatory therapy the median concentration of NPA ECP was 882 ng/g in those with physician-diagnosed wheezing (P = 0.02). The NPA ECP concentration of the whole study group of 88 children with and without subsequent hospital admissions for wheezing were 531 and 299 ng/g, respectively (P = 0.02). At entry the children with negative viral findings had significantly higher concentrations of respiratory tract ECP than those with positive viral findings (515 vs. 240 ng/g; P = 0.01). The concentration of ECP in respiratory secretions decreased significantly after bronchiolitis (P = 0.01) provided that no new viral or mycoplasmal infection occurred. NPA ECP values decreased in relation to time regardless of whether anti-inflammatory therapy was used or not. Children with high concentrations of respiratory tract ECP seemed to benefit from anti-inflammatory therapy with nebulized cromolyn sodium or budesonide; both drugs significantly decreased the number of subsequent physician-diagnosed bronchial obstruction (P = 0.0006), and they tended to decrease the number of hospital admissions for wheezing (P = 0.08). Our results suggest that high concentrations of ECP in respiratory tract secretions in children with bronchiolitis reflect the presence of eosinophilic inflammation also seen in asthma.

Serum eosinophil cationic protein as a predictor of wheezing after bronchiolitis

We have evaluated the role of eosinophil cationic protein (ECP) concentrations in serum in predicting wheezing after bronchiolitis, during infancy and early childhood. A prospective study at a university hospital serving all pediatric patients in a defined area was designed. Serum ECP concentrations were measured in 92 infants under the age of 2 years on admission for acute bronchiolitis, and 6 and 16 weeks after hospitalization. Nebulized anti-inflammatory therapy was initiated during hospitalization: 32 patients received cromolyn sodium and 32 patients received budesonide for 16 weeks; 30 control patients received no maintenance therapy. The numbers of subsequent physician-diagnosed wheezing episodes and hospital admissions for obstructive airway disease were recorded during 16 weeks of follow-up. At entry, 14 of 92 (15%) children had high (> or = 16 micrograms/L) levels of ECP in their serum. During the 16-week follow-up period, this group of patients had significantly more physician-diagnosed episodes of wheezing (86% vs. 43%, P < 0.01) and hospital admissions for wheezing (64% vs. 19%, P = 0.001) than those with serum levels of ECP < 16 micrograms/L. The number of patients with serum ECP > or = 8 micrograms/L was 25 (27%); 76% of this group developed physician-diagnosed wheezing (P < 0.01), and 48% had hospital admissions for wheezing (P < 0.01). Serum ECP levels decreased significantly with respect to time after bronchiolitis and did not differ among the three intervention groups. We conclude that a high serum ECP concentration during the acute phase of bronchiolitis is a specific but insensitive predictor of wheezing after bronchiolitis.

Detection of antibodies to Mycoplasma pneumoniae adhesion P1 in serum specimens from infected and non-infected subjects by immunoblotting

Paired serum specimens from 17 patients with Mycoplasma pneumoniae infection, as demonstrated by a rise in complement fixation (CF) antibody titer and 14 single sera, negative in the CF test, were tested for the presence of Ig A, Ig G, and Ig M antibodies to a polypeptide with a molecular weight of 170 KDa (P1) in an immunoblot assay. In acute phase sera, collected in the 1st week of the disease, frequency of occurrence of the antibodies against P1 protein did not exceed 18%. Two to three weeks later, Ig A antibodies were detectable in 82.4%, Ig M in 76.5%, and Ig G antibodies in all convalescent phase sera. No sera negative in the CF test (titer < 4) had antibodies against M. pneumoniae adhesin P1.

Bacterial antibody assays in the diagnosis of acute lower respiratory tract infection in children

Bacterial antibodies were studied in acute, intermediate and convalescent phase sera (mean duration from first to last sample 36 days) of 121 children hospitalized for acute lower respiratory tract infection. Antibody responses were observed in 45% of all cases and in 29% of the 21 children < 1 year old. A total of 15 responses to Streptococcus pneumoniae (pneumolysin), 20 to Haemophilus influenzae, 9 to Moraxella catarrhalis, 3 to chlamydiae and 8 to Mycoplasma pneumoniae were found. In 79 patients with 4 consecutive samples available, 52% of the 31 responses were measurable within 5 days from admission. Overall the responses were not associated with upper respiratory tract bacterial findings or acute otitis media. Significantly more responses were found in the 121 children with acute lower respiratory tract infection than in healthy controls (P < 0.007). We conclude that bacterial antibody assays provide a useful tool in the study of the etiology of acute lower respiratory tract infection in young children, even if the interval between paired serum samples is short.

Comparison of three serological methods for diagnosing Mycoplasma pneumoniae infection

AIMS

To compare the novel Serofast latex agglutination test (International Mycoplasma, Toulon-Cedex, France) with the complement fixation test and enzyme immunoassay (EIA) for diagnosing acute Mycoplasma pneumoniae infection.

METHODS

Paired sera from 60 patients with respiratory infection who had tested positive for M pneumoniae by complement fixation test were analysed with Serofast and indirect EIA for specific IgG and IgM antibodies.

RESULTS

Serofast was less sensitive than the two other tests. Only 30 (50%) out of 60 paired sera which showed a diagnostic seroconversion or had high positive, unchanged antibody titres by complement fixation test or EIA, or both, tested positive with Serofast. Positive test results with Serofast were associated with the presence of a complement fixation test titre of > or = 512 and high positive IgM antibody titres measurable by EIA; virtually all patients with a complement fixation test titre of < 256 or those responding primarily in the IgG class tested negative with Serofast. Based on analysis of sera taken at the acute phase of infection, 10 (17%) of the 60 patients tested positive by complement fixation test, 10 (17%) by EIA, and only four (7%) by Serofast.

CONCLUSIONS

Serofast was less sensitive than complement fixation test and EIA and it cannot be recommended as a replacement for either test in routine diagnostic use. It might prove useful in laboratories where non-specific tests, such as the determination of cold agglutinins, are still used for the diagnosis of M pneumoniae infection. Testing paired sera is, however, a prerequisite for obtaining acceptable sensitivity by Serofast as well as other serological methods currently available.

Evaluation of an antigen-capture enzyme immunoassay for rapid diagnosis of Mycoplasma pneumoniae infection

A new enzyme immunoassay (EIA; Enzygost) for rapid detection of Mycoplasma pneumoniae antigen was evaluated in 51 young adults with acute respiratory infection. The EIA results using sputa and nasopharyngeal aspirates were compared with those of serological antibody tests, culture and a DNA probe. In sputum the sensitivity of the EIA ranged from 40% to 81% and the specificity from 64% to 100%, depending on the reference method. In nasopharyngeal aspirates the sensitivity was well below 20%, but the test was nearly 100% specific.

An epidemic of infections due to Chlamydia pneumoniae in military conscripts

A prospective observational study of an epidemic of infection due to Chlamydia pneumoniae strain TWAR in Finnish military trainees provided new information on immunity following infection, the range of clinical syndromes and complications, and cell culture isolation. One-half of the trainees studied (43 of 86) had laboratory evidence of C. pneumoniae infection. The etiologic association of C. pneumoniae with disease was strengthened by the sharp increase in cases of pneumonia and in outpatient visits for acute respiratory disease along with the laboratory evidence of infection. The pattern of serological response suggested that 23 of the trainees had a primary TWAR infection and 20 had a reinfection. Evidence that prior infection modified the illness included the frequency of hospitalization (12 with primary infections vs. 1 with reinfection), the development of pneumonia (10 vs. 0), and the requirement for repeated courses of antibiotic therapy (13 courses vs. 0). Isolation was more frequent in HL cells (n = 25) than in HeLa 229 cells (n = 10).

Mycoplasma pneumoniae and Chlamydia trachomatis in acute lower respiratory infections in Filipino children

The role of Mycoplasma pneumoniae and Chlamydia trachomatis in acute lower respiratory infection (ALRI) was studied by serologic analysis of 216 Filipino children less than five years old living in periurban slums and middle-class neighborhoods. Diagnostic antibody responses to M. pneumoniae and C. trachomatis were observed in 18 (8.3%) and five (4.3%), respectively, of the cases with ALRI. These bacteria are not susceptible to the antimicrobial treatments currently recommended for the treatment of ALRI in developing countries.

Preceding respiratory infection predisposing for primary and secondary invasive Haemophilus influenzae type b disease

Cases (117) with invasive Haemophilus influenzae type b (Hib) disease and their family members reported symptoms of respiratory infection during the 4-week period before the onset of Hib disease significantly more often than age-, sex- and residence-matched controls (225) and their family members during the same time period. Viral (adenovirus; influenza A and B; parainfluenza types 1, 2 and 3; and respiratory syncytial virus) and Mycoplasma pneumoniae serology was performed in 84 paired sera from cases and 112 paired sera from controls, who were healthy children matched to the cases by age, year and season. Viral or M. pneumoniae infection was diagnosed equally often among cases and controls (18% for both groups). However, patients who were associated cases of Hib disease (i.e. either the primary or secondary case of a case pair) had a diagnostic viral serology more often (50%) than did sporadic cases (13%) (odds ratio, 7.0; 95% confidence interval, 1.6 to 33; P = 0.006). These results suggest that some infectious agent(s) caused symptoms among the patients and circulated among the patients' closest contacts immediately before their development of Hib disease and possibly predisposed for invasive Hib disease. For the development of associated Hib disease among close contacts of an index case, adenovirus, influenza A, respiratory syncytial virus or para-influenza type 1, 2 and 3 infections may be important.

Vaccination-induced HI antibody to influenza A(H1N1) viruses in poorly primed adults under circumstances of low antigenic drift

In Autumn 1990, trivalent split influenza virus vaccine containing A/Taiwan/1/86(H1N1) was used to immunize healthy female employees (n = 104). The 11-12 amino acid differences in the HA1 domain of virus haemagglutinin between A/Taiwan/1/86 and representative epidemic H1N1 strains in Finland in 1991 did not result in lowered haemagglutination-inhibiting (HI) antibody responses to the latter viruses. In fact, higher prevaccination, postvaccination and postepidemic antibody titres were recorded against the new field strains than against the vaccine virus; the highest being against field strains grown exclusively in MDCK cell cultures. This pattern is primarily explained by differences in the sensitivity of the viruses for detecting HI antibodies. Postvaccination protection rates of 98-100% for the MDCK-grown avid viruses were noted in subjects who exhibited prevaccination antibody. Lower protection rates were recorded in initially seronegative subjects, the lowest (54-57%) being among older people, i.e. among vaccines born in 1930-1955 (p < 0.001). Moreover, conspicuous decreases in protection rates were detected during the following epidemic season in the initially seronegative subjects. Diagnostic findings during outbreaks due to H1N1 subtype viruses also support the impression that many middle-aged people are poorly primed. Thus, vaccination with two doses may be worth considering when such people join the high-risk group and receive influenza vaccine for the first time.

Outbreak of Mycoplasma pneumoniae infection among hospital personnel studied by a nucleic acid hybridization test

An outbreak of Mycoplasma pneumoniae (MP) infection occurred during the period March-May 1989 among the personnel of the Accident and Emergency Department of the Kuopio University Hospital, Kuopio, Finland. The index patient was a young male orderly, who fell ill with severe pneumonia. His tracheal mucus sample proved to be strongly positive for MP when tested by a commercial DNA-RNA hybridization test (Gen-Probe). After the index patient two additional staff members (an orderly and a nurse) fell ill with pneumonia and 66 others showed symptoms of upper respiratory infection or fever. The most frequent symptoms were a sore throat, a cough, rhinitis and headaches. All 97 employees of the department were tested for the presence of MP in April-May 1989 using throat swabs as test material. Forty-three (44%) were found to be positive for MP by the 'Gen-Probe' test. Eight (19%) of the MP positive staff were completely asymptomatic. The MP positive staff were retested about 3 weeks later, whereupon 40 (93%) had become negative. Most of the persons involved in this outbreak suffered only from mild respiratory symptoms, suggesting that MP outbreaks like the present one may easily pass unnoticed.

Immune response to inactivated influenza virus vaccine: antibody reactivity with epidemic influenza B viruses of two highly distinct evolutionary lineages

Vaccination of adults (healthy female employees potentially capable of transmitting influenza to high-risk persons; n = 104) in autumn 1990 with a trivalent influenza virus vaccine containing B/Yamagata/16/88 induced a low antibody response to B/Finland/150/90, a recent variant of B/Victoria/2/87-like viruses, as compared with the antibody response to B/Finland/172/91, a current variant in the lineage of B/Yamagata/16/88-like viruses. Up to the end of the epidemic season, the antibody status declined but was still significantly better than before the vaccination. The results suggest that the vaccine strain was appropriate for the outbreak of 1990 to 1991 in Finland, but may provide unsatisfactory protection against B/Victoria/2/87-like viruses. Evidence is given that use of Madin-Darby canine kidney (MDCK)-grown virus as an antigen in the haemagglutination inhibition test (HI) may provide more reliable information about the protective antibodies than use of untreated or ether-treated egg-grown viruses. Significantly higher postvaccination and postepidemic antibody titres were recorded among subjects who exhibited the antibody before vaccination than among seronegative subjects. A significantly higher response rate among initially seronegative people than among seropositive people was recorded for antibody to B/Finland/150/90, but no clear evidence was obtained that the pre-existing antibody could have had a negative effect on the antibody production.

The causes of hospital-treated acute lower respiratory tract infection in children

OBJECTIVE

To determine the etiologic agents in children with acute lower respiratory infection.

DESIGN

A survey of a series of patients.

SETTING

General pediatric hospital serving an urban population with and without referrals in Helsinki, Finland.

PARTICIPANTS

135 Finnish children aged 2 months to 15 years (mean, 1.75 years), with clinically defined acute lower respiratory infection (with difficulty of breathing), or found to have fever and a pneumonic infiltrate on chest roentgenogram.

SELECTION PROCEDURES

Consecutive sample on voluntary basis.

INTERVENTIONS

None.

MAIN RESULTS

Of 121 children with adequate samples, an etiologic diagnosis could be established in 84 (70%): 30 (25%) had bacterial, 30 (25%) viral, and 24 (20%) mixed infections. Antibody assays alone identified the agent in 91% of positive cases.

CONCLUSIONS

Bacterial infections are common but generally underestimated in acute lower respiratory infection; serologic methods add significantly to their detection.

Serum adenosine deaminase in viral and bacterial pneumonia

We measured the activity of serum adenosine deaminase (ADA) in paired sera from 171 military conscripts with radiographically verified pneumonia. Patient serum samples were selected on the basis of serologic analyses identifying as single etiologic agents Streptococcus pneumoniae in 29 patients, Haemophilus influenzae in 7, Mycoplasma pneumoniae in 43, adenovirus in 24, influenza A or B in 12, and parainfluenza in 5 patients. In 14 patients Neisseria meningitidis and in 31 Chlamydia spp were considered the main etiologic agent. Compared with a control group of 45 healthy men, the ADA activity in patients with pneumonia was significantly higher (p less than 0.001) in all patient groups except those with meningococcal pneumonia. The highest ADA levels were seen in patients with pneumonia caused by M pneumoniae (27.4 +/- 9.7 U/L), Chlamydia spp (26.3 +/- 9.1 U/L), and adenovirus (28.5 +/- 10.9 U/L) compared with the controls (11.1 +/- 3.0 U/L). In patients with meningococcal pneumonia, the ADA activity was significantly decreased (p less than 0.001). Serum ADA activity probably reflects differences in cellular immune response to different infectious agents. The ADA determinations may give corroborative information on the etiologic agent of pneumonia.

Viral antibodies in multiple sclerosis. A nationwide co-twin study

Serum viral antibody titers against 21 viruses were studied in 19 of 23 same-sex twin pairs with multiple sclerosis derived from the Finnish Twin Cohort. Thorough neurologic examinations showed two monozygotic pairs to be concordant, whereas all dizygotic pairs were discordant. Special attention was given to measles, mumps, and rubella viruses, against which the antibody levels were determined with the complement fixation, hemagglutination inhibition, hemolysis-ingel, and enzyme immunoassay methods. Epstein-Barr virus antibody levels were determined by enzyme assay. In pairwise comparisons, the measles, mumps, and Epstein-Barr virus-IgG antibody levels were more often elevated in the patients with multiple sclerosis, compared with the healthy co-twins. The same antibody levels were more often above the median in the diseased twin, compared with the healthy twin, but the difference was not significant. No human T-cell lymphotropic virus type I antibodies were found in any of the individuals examined. The total IgG, IgA, and IgM levels did not differ between the diseased and healthy subjects. The HLA types, severity of the disease, and cell-mediated immunity parameters did not influence antibody levels.

MS and SLE in twins of successive generations

During a nationwide twin study on multiple sclerosis (MS) in Finland a dizygotic pair discordant for MS was found. The affected co-twin had dizygotic twin daughters. The affected co-twin of the second generation had systemic lupus erythematosus (SLE). Both pairs were thoroughly examined. No evidence of CNS involvement in the healthy co-twins was found. In pairwise comparisons, virus-specific IgG antibodies to measles and mumps were significantly increased in the MS patient whereas the same was true for rubella in the SLE patient. Both MS and SLE patient expressed HLA alleles most often found to be associated with these disorders. Reversed CD4/CD8 ratios were observed in both MS and SLE patient. No difference in interleukin-2 receptor expression were found but gamma-interferon secretion in the MS patient showed marked increase whereas that of the SLE patient was of the same magnitude as in the healthy members. A different triggering stimulus rather than the dissimilarity in the immunogenetic predisposition may be decisive as to whether or not they develop MS or SLE.

Serological evidence of viral or Mycoplasma pneumoniae infection in acute maxillary sinusitis

Evidence for the involvement of viruses, Mycoplasma pneumoniae, and Chlamydia spp. was studied by the complement fixation test in paired sera from 310 young adults (297 men and 13 women) with acute maxillary sinusitis. The diagnosis of acute sinusitis was confirmed by radiography and sinus puncture. Elevated antibody titres were found in 102 patients (33%). A four fold or greater titre rise was detected in 21.5%, and a high stable titre suggestive of recent viral infection was present in a further 11.5%. Adenovirus, influenza A and B viruses, and Mycoplasma pneumoniae accounted for most of the elevated antibody titres. Elevated titres were found in 79 (32%) of the 245 patients with purulent maxillary sinusitis (pathogenic bacteria isolated in sinus secretion) and in 23 (35%) of the 65 patients with non-purulent sinusitis (no pathogenic bacteria isolated). About 90% of the fourfold or greater titre rises in bacteriologically negative cases were due to adeno- or influenza viruses. A fourfold rise in antibody titre was also found in 7 of 101 control patients (7%). The results of this study suggest that respiratory viruses and Mycoplasma pneumoniae may be potential etiological agents in acute maxillary sinusitis, either alone or in combination with the common bacterial pathogens of sinusitis.

Epidemics of pneumonia caused by TWAR, a new Chlamydia organism, in military trainees in Finland

Four epidemics of pneumonia in military trainees in Finland have been shown, by microimmunofluorescence serology, to have been caused by TWAR, a recently described, unique Chlamydia organism. The epidemics occurred in four different garrisons from 1957 to 1985. Each lasted approximately six months, and epidemics occurred during all seasons of the year. The attack rate varied from 60 to 80 per 1000 men. Routine laboratory tests for respiratory agents suggested that these epidemics represented the only clusters of patients since 1970 who were positive for antibody to Chlamydia by complement fixation. From these epidemics, 62 of 70 paired sera that were positive for Chlamydia had antibody diagnostic of recent TWAR infection. Although the conscripts with pneumonia were hospitalized, the illnesses were relatively mild, and none were life threatening. Three conscripts had two episodes of TWAR pneumonia separated by three weeks to three months. Prompt treatment with tetracycline depressed the antibody response.

The role of parainfluenza viruses in inspiratory difficulties in children

Viral findings were prospectively studied in middle and lower respiratory tract infections in 449 hospitalized children during a 12-month follow-up period. A viral aetiology was found in 30 of the 65 children (46%) with inspiratory difficulties. Parainfluenza viruses were the infective agents in 24 of the 30 cases with viral diagnoses (80%), type 2 being the most prominent. There were 38 cases of parainfluenza infections, type 2 being the infective agent in 58% of the 24 cases of parainfluenza infections with inspiratory difficulties but in only 21% of the 14 cases of parainfluenza infections without inspiratory difficulties. Type 2 parainfluenza virus produced inspiratory difficulties in 82% of the cases as opposed to 56 and 50% of the cases for type 1 and 3, respectively. It is concluded that the type 2 parainfluenza virus has a particular association with inspiratory difficulties in children. Viral diagnosis was reached using direct antigen detection in nasopharyngeal specimens by radioimmunoassay in 59% and using complement fixation serology in 76% of parainfluenza infections. Direct antigen detection was especially useful in infants. We suggest that direct antigen detection should be used as a primary virological diagnostic method in small children with middle and lower respiratory tract infections.

Localized outbreak of enteroviral meningitis in adults

During a thorough surveillance of viral infections of the central nervous system an outbreak of aseptic meningitis was discovered in the western part of Finland in late 1985. The 21 diseased young adults were carefully studied by different virological methods. A presumed viral etiology, in all cases of enteroviral origin, was found in 16 of 20 (80%) with adequate specimens. Four different enteroviruses were associated with this episode; in 9 cases the presumed etiological agent was echovirus 5, while coxsackie B5, echo 25 and echo 17 viruses appeared to be responsible for 4, 2 and 1 case, respectively. Sensitivity of different diagnostic methods as regards detection of the echovirus 5 infections was in order: increase of type-specific neutralizing serum antibodies, isolation of virus from faeces, isolation from throat and group diagnosis by demonstrating an increase in complement-fixing antibodies to coxsackie B5 virus antigen.

Anticardiolipin response in acute infections

Paired serum specimens from 149 patients with six different infections verified by a significant rise in the specific antibody level were tested for anticardiolipin antibodies using enzyme-linked immunosorbent assay. Significantly raised levels, at least in one immunoglobulin class, were detected in 32% of the cases, and significant changes in the level indicating an ongoing process, in 26%. Taken as a whole, the response involved the immunoglobulins IgG, IgM, and IgA, although in patients with mumps the significantly raised levels were virtually confined to the IgA class. The binding of syphilitic antibodies to solid-phase cardiolipin was readily inhibited by cardiolipin liposomes, whereas this pattern of reactivity was noted in only one of four nonsyphilitic sera. It was concluded that anticardiolipin antibodies occur very frequently in a wide variety of uncomplicated infections.

Viral findings in children under the age of two years with expiratory difficulties

Viral findings were prospectively studied in lower respiratory tract infections in small children with and without expiratory difficulties. On first admission, a viral aetiology was found in 71 of 127 children (56%). On re-admission, a viral etiology was found in only two of 31 cases (6%). Respiratory syncytial viruses (RSV) were responsible for 71% of the cases with viral diagnoses. A recently-developed method for the direct detection of viral antigens in nasopharyngeal specimens by radio-immunoassay was more sensitive than complement fixation serology, especially in patients aged less than six months. Viral diagnosis was reached using this new method alone in 43% of infections caused by RSV and in 27% of infections caused by other viruses. In children under six months, RSV were found in 89% by direct antigen detection and in 22% by serology. We suggest that direct antigen detection should be used as the primary virological method in small children with lower respiratory tract infections. The aetiological agents were the same in cases with and without expiratory difficulties, RSV being found in about 40% of children in both instances. It is concluded that host factors are critical to the development of expiratory difficulties.

The HI test modified by ether treatment in the sero-epidemiological surveillance of influenza B

Ether-treated influenza B haemagglutination inhibition (HI) antigen was used in a study of serum collections from three different epidemic seasons. For diagnostic purposes, ether treatment increased the efficacy of the HI test by about 50% over the conventional HI technique, raising it to the same level of sensitivity as the complement fixation (CF) test. The treatment reduced the specificity of the HI test, but its reliability in the diagnosis of influenza B infections was only slightly diminished. With regard to evaluation of the immune status of a given population, an HI test using ether-treated antigen from the epidemic influenza B strain seems to give more relevant information about the antibody level associated with protection than a conventional HI test using untreated virus antigen.

An epidemic of mild pneumonia due to an unusual strain of Chlamydia psittaci

An epidemic of mild pneumonia was discovered during a chest radiographic survey of adolescents and young adults in two communities 110 kilometers apart in northern Finland. Antibodies to chlamydial antigens were found in 32 of 34 persons with pneumonitis. Microimmunofluorescence antibody tests suggest that the etiologic agent is closely related or identical to TW-183, an unusual strain of Chlamydia psittaci isolated from the eye of a child in Taiwan. The point prevalence of pneumonitis with antibody to TW-183 in school children at the time of the survey was high-15 and 19 patients per 1,000 students in the two communities. There was no evidence of avian transmission in the epidemic.

Serological diagnosis of influenza A and B infections by enzyme immunoassay. Comparison with the complement fixation test

Paired sera from 784 patients with symptoms of acute respiratory disease were examined for antibodies against influenza A, B and parainfluenza (1 and 3) viruses by complement fixation (CF) and enzyme immunoassay (EIA). The internal variation of the EIA test results was low and an increase of 0.250 in absorbance values which corresponded to a two-fold increase in end-point titres was considered a diagnostic antibody rise. EIA detected significantly more diagnostic rises than the CF test in the case of influenza A (222 vs. 162, P less than 0.001) and parainfluenza virus antibodies (29 vs. 16, P less than 0.01). More diagnostic rises in influenza B antibodies were also observed by EIA compared to the CF test (104 vs. 99, not significant). There were only two patients who showed a diagnostic rise in CF antibodies (both influenza B) but not in EIA. Most often patients with a diagnostic antibody rise only by the EIA method had a two-fold rise in the respective CF antibodies (68% of cases). EIA was found to be a sensitive and reliable method for the serological diagnosis of influenza A, B and parainfluenza infections.

Immunologically related ketodeoxyoctonate-containing structures in Chlamydia trachomatis, Re mutants of Salmonella species, and Acinetobacter calcoaceticus var. anitratus

The lipopolysaccharides (LPS) of Chlamydia trachomatis, Acinetobacter calcoaceticus var. anitratus, and Re mutants of Salmonella sp. were shown to share related immunodeterminants , as demonstrated by double immunodiffusion and immunoblotting from sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels. The cross-reactive material in the extracellular slime of A. calcoaceticus var. anitratus was shown to be released LPS. The Acinetobacter LPS was found to separate in sodium dodecyl sulfate-polyacrylamide gel electrophoresis into three fractions. The cross-reactive component was the fraction migrating fastest, at a rate identical to Re-type LPS of Salmonella sp. The Acinetobacter LPS could be used as antigen in complement fixation assays performed on paired sera of patients with chlamydial pneumonia; it gave results identical to those of the chlamydial complement fixation glycolipid antigen conventionally used in such assays in 9 of 10 patients.

Increase in titers of antibodies to Mycoplasma pneumoniae in patients with purulent meningitis

A fourfold or greater increase in titer of complement-fixing (CF) antibodies to Mycoplasma pneumoniae was found in 40.7% of paired sera from 54 patients with bacterial meningitis that had been proven by culture and in 10.3% of 39 patients with other bacteremic infections, but in none of eight patients with whooping cough or 40 patients with mumps meningitis. The CF antigen used was a crude lipid antigen, but comparable antibody increases were found by an enzyme-linked immunosorbent assay using a crude M. pneumoniae protein antigen. Increases were also frequently seen in nonspecific antibodies to the capsular polysaccharide of group A Neisseria meningitidis; these increases were significantly, but not completely, correlated to the nonspecific reactions to the mycoplasmal antigens. The data call for caution in interpreting serologic tests for M. pneumoniae when dealing with diseases not commonly associated with M. pneumoniae.

Neurological diseases associated with viral and Mycoplasma pneumoniae infections

In 1963 the World Health Organization established a system for the collection and dissemination of information on viral infections and by 1976, laboratories in 49 countries were participating in this scheme. The present study is in two parts: part 1 is an analysis of almost 60 000 reports on neurological disease associated with viral and Mycoplasma pneumoniae infections reported during the 10-year period 1967-76. This analysis showed a steady increase in the yearly number of reports of viral neurological diseases, which closely followed the general increase in the overall reporting of virus diseases. Likewise, the seasonal pattern was similar to that seen in general for any given virus.Over 75% of the cases were in children. Over half of all viral neurological diseases were associated with enteroviruses, while the myxoviruses accounted for almost 30%. Among the myxoviruses, mumps virus was by far the most frequently reported. The polioviruses were the agents most commonly detected in cases of paralytic disease. The other enteroviruses, mumps virus, and the herpesviruses were the most frequently reported viruses in cases of aseptic meningitis or encephalitis. On the other hand, one-third to over one-half of the reports on the myxoviruses (excluding mumps and measles) related to ill-defined clinical conditions.Part 2 of the study deals in particular with viruses whose role in neurological disease is less well documented. One laboratory reported an outbreak of adenoviral aseptic meningitis in Czechoslovakia, while another described neurological disease associated with M. pneumoniae infection in Finland. Part 2 also includes a detailed appraisal of viral infections diagnosed in the Netherlands during the period 1973-76. The results are very similar to those routinely reported.

The value of complement fixation and haemagglutination inhibition tests in the diagnosis of influenza A

Antibody response of 133 influenza A patients from three outbreaks since 1972-73 was analyzed by complement fixation (CF) and haemagglutination inhibition (HI) methods. During the first outbreak, a significant response was more often measured by CF than by HI. During the last outbreak HI appeared more useful than CF for routine serological diagnosis; 23% of cases verified by HI were missed by CF. The poor response of CF antibodies was associated with the high level of pre-infection antibodies.