Viruses of Diseases of the Respiratory Tract
Authors: C. H. Stuart-Harris
Journal: BMJ (1962)

The usual methods for determining the prevalence of infectious disease in the community by notification of cases or by mortality records fail to provide the proper background for acute respiratory disease.This is because of the largely benign character of the illnesses and also the great difficulty in their clinical differentiation.There are of course available the notifications of pneumonia and the deaths from bronchitis, pneumonia, and influenza which certainly give valuable indications of the presence of influenza viruses in the community.Influenza epidemics are also identified by the high attack- rate in adults and illnesses in the insured population which cause a sudden excess in the number of claims from National Insurance.Excluding influenza, however, one is left with the major portion of the commoni respiratory diseases on which there is little exact information beyond their seasonal character.Every year, from October to March, there is a seasonal rise in all sickness insurance claims, particularly in those from acute respiratory illnesses.Epidemics such as influenza are associated with the largest increases.Abrupt increase in illnesses occurs at other times, how- ever, and those in patients needing admission to hospital are well shown by statistics from the London Emergency Bed Service and kindly made available to me by Dr. Godber, of the Ministry of Health (see Fig.).These admissions undergo successive increases and decreases between October and April, and sharp increases occur particularly between December and February.Fogs and influenza epidemics are identifiable causes of some increases, but others are of unknown origin.Though the patients concerned are largely those with chronic disease of the ch^st and heart, the illnesses for which they are admitted are acute episodes of bronchitis or pneumonia with or without heart failure.Sometimes also infants and children are involved in a sudden flurry of admissiorns from bronchiolitis (Nicol, 1957).Holland, Spicer, and Wilson (1961) recently analysed hospital admissions from the E.B.S. during 1958 in such a way as to eliminate purely seasonal changes.A positive correlation was found between increases in atmospheric pollution or falls of temperature and increases in admis- sions in those aged 15 years or more.In a further study of three large recruiting stations of the R.A.F.where pollution was not a problem there was a similar correla- tion between increase in acute respiratory disease and cold weather.Hope-Simpson (1958) has also demonstrated a most striking correlation between increase in the frequency *The second of two Croonian Lectures delivered before the Royal College of Physicians of London on March 13 and 15, 1962.The first lecture appeared in the issue of June 30, 1962. of colds in a group of families in a country practice and falls in temperature recorded in the soil.Such correlations may of course be indicative of the provocative effect of environmental agencies on the host-virus relationship rather than a direct effect upon the hosts themselves.But it is also necessary to consider the effect of different humidities on the survival of viruses.Hemmes, Winkler, and Kool (1960) have found that poliovirus survives exposure to moist better than to dry air.Common-cold viruses (Tyrrell, 1961) also prefer a high relative humidity whereas influenza virus survives better in dry air.The weather may therefore provide EMERGENCY BED SERVICE IL