K. G. Nicholson

OBJECTIVE: To study the role of respiratory viruses in exacerbations of asthma in adults. DESIGN: Longitudinal study of 138 adults with asthma. SETTING: Leicestershire Health Authority. SUBJECTS: 48 men and 90 women 19-46 years of age with a mean duration of wheeze of 19.6 years. 75% received regular treatment with bronchodilators; 89% gave a history of eczema, hay fever, allergic rhinitis, nasal polyps, or allergies; 38% had been admitted to hospital with asthma. MAIN OUTCOME MEASURES: Symptomatic colds and asthma exacerbations; objective exacerbations of asthma with > or = 50 l/min reduction in mean peak expiratory flow rate when morning and night time readings on days 1-7 after onset of symptoms were compared with rates during an asymptomatic control period; laboratory confirmed respiratory tract infections. RESULTS: Colds were reported in 80% (223/280) of episodes with symptoms of wheeze, chest tightness, or breathlessness, and 89% (223/250) of colds were associated with asthma symptoms. 24% of 115 laboratory confirmed non-bacterial infections were associated with reductions in mean peak expiratory flow rate > or = 50 l/min through days 1-7 and 48% had mean decreases > or = 25 l/min. 44% of episodes with mean decreases in flow rate > or = 50 l/min were associated with laboratory confirmed infections. Infections with rhinoviruses, coronaviruses OC43 and 229E, influenza B, respiratory syncytial virus, parainfluenza virus, and chlamydia were all associated with objective evidence of an exacerbation of asthma. CONCLUSIONS: These findings show that asthma symptoms and reductions in peak flow are often associated with colds and respiratory viruses; respiratory virus infections commonly cause or are associated with exacerbations of asthma in adults.

BACKGROUND: The polymerase chain reaction has improved the detection of picornaviruses and rhinoviruses and our understanding of their role in reversible airways disease. The effects of colds on lower respiratory morbidity and bacterial colonisation in cystic fibrosis remain uncertain. METHODS: Children with cystic fibrosis were evaluated regularly in the clinic and the parents notified the investigators when their child developed a cold. Nasopharyngeal specimens were collected at the start of the infection for polymerase chain reaction, bacteriology was also undertaken and again three weeks later, and pulmonary function was measured in children aged > or = 6 years at four day intervals for three weeks. The effects of colds on rate of progression of cystic fibrosis were assessed by pulmonary function, Shwachman scores, and radiology. RESULTS: Thirty eight children suffered 147 colds over 17 months. Picornaviruses were detected in 51 (43%) of 119 nasopharyngeal specimens, and 21 of the 51 were further identified as rhinoviruses. Pulmonary dysfunction was similar following picornavirus and non-picornavirus infections; the mean change from baseline in forced expiratory volume in one second (FEV1) was -16.5% and -10.3% at 1-4 days and 21-24 days, respectively, after onset of a cold. Children who experienced more colds than average had evidence of disease progression with reduction in Shwachman score, increasing Chrispin-Norman score, and greater deterioration in FEV1 per annum. Ten of 12 new bacterial infections were associated with a cold. CONCLUSIONS: Picornavirus and non-picornavirus colds are associated with pulmonary function abnormalities and disease progression in patients with cystic fibrosis, and predispose to secondary bacterial infection and colonisation.

The effects of influenza A and B and RSV on mortality in England and Wales were assessed by regression analysis for the period 1975-90. Morbidity data from sentinel practices were used to calculate 4-weekly rates of aggregated upper respiratory tract infections (URTI); PHLS laboratory reports were used as indices of infection, and 4-weekly death rates from all causes, excluding childbirths, were used to study relationships with mortality. Deaths correlated strongly with influenza A and B reports, temperature, and interactions between aggregated URTI and temperature, and RSV outbreaks and temperature. Estimates of 'seasonal' 4-weekly mortality associated with URTI were made by substituting into primary regression models the mean of annual trough consultation rates for aggregated URTI and baseline values for RSV and influenza. Peak 4-weekly mortality associated with URTIs was estimated at c. 24000 and c. 28000 during combined influenza and RSV epidemics of 1975-6 and 1989-90 respectively. Secondary regression analysis was carried out with the estimated 'seasonal' 4-weekly deaths associated with URTI as dependent variable and laboratory data as regressors. Estimated excess mortality associated with influenza was considerable even during years without major epidemics. Overall during the 15 winters the estimated mortality associated with RSV was 60-80% more than that associated with influenza. The modelling permits only a crude estimate of RSV associated mortality. None the less it suggests that RSV is an important cause of winter mortality.

The effectiveness of influenza vaccination in reducing hospitalization of people with diabetes for influenza, pneumonia, or diabetic events during influenza epidemics was assessed in a case control study in Leicestershire, England. Cases were 80 patients on the Leicestershire Diabetes Register who were admitted and discharged from hospital with International Classification of Disease codes for pneumonia, bronchitis, influenza, diabetic ketoacidosis, coma and diabetes, without mention of complications, during the influenza epidemics of 1989-90 and 1993. One hundred and sixty-controls, who were not admitted to hospital during this period, were randomly selected from the Register. Immunization against influenza was assessed in 37 cases and 77 controls for whom consent was obtained to access their clinical notes and for whom notes were available. Significant association was detected between reduction in hospitalization and influenza vaccination during the period immediately preceding an epidemic. Multiple logistic regression analysis estimated that influenza vaccination reduced hospital admissions by 79% (95% CI 19-95%) during the two epidemics, after adjustment for potential confounders.