Winter is traditionally a time when respiratory infections are common amongst the population. Although most of these are not serious in the vast majority of individuals, they can cause complications particularly for those who are immunocompromised and, for example, those with chronic cardiac, respiratory or renal disease. They are also responsible for significant morbidity in the community and associated socio-economic burdens, for example, increases in the workload of healthcare workers, absence from work and non-attendance in schools.

Viral infections are responsible for a large proportion of flu-like illnesses. The majority of infections in otherwise healthy individuals are self-limiting (ie will resolve without treatment). For others, including the elderly, children and the immunocompromised, they can lead to more serious complications and even death.

Coxiella burnetii

Q fever is caused by Coxiella burnetii. Infection is endemic in cattle, sheep and goats, and thus it is most often occupationally acquired by abattoir workers, veterinarians, farmers etc. Transmission is by aerosol or environments contaminated by parturition (birth) products, and on rare occasions by unpasteurised milk.

Influenza

Three types of influenza virus are recognised, A, B and C. Type A viruses cause most epidemics and can cause worldwide epidemics (pandemics). The main pandemics this century were in 1918, 1957 and 1968. The largest in 1918, caused approximately 20 million deaths worldwide and it is estimated that 23% of the United Kingdom population developed influenza that year. In the United Kingdom, influenza A activity increases, although not necessarily to epidemic levels, most winters. Type B can also cause outbreaks, usually between outbreaks of influenza A; however they tend to be less extensive and are usually associated with less severe illness. Type C is linked with sporadic cases and minor localised outbreaks and is of relatively little importance. Clinical attack rates during epidemics range from 10%-30% in the general community to greater than 50% in institutions. Influenza is spread by the airborne route particularly among crowded populations in enclosed spaces.

Legionnaires' Disease

Legionnaires' Disease is so-called because it was first detected at a convention of American Legion members in Philadelphia in 1976. It is caused by the bacterium Legionella pneumophila, and presents as pneumonia, with a dry non-productive cough and severe 'flu-like symptoms. It can occur sporadically as an uncommon cause of community-acquired pneumonia, or as cases associated with environmental sources such as hospitals, hotels and factories.

Mycoplasma pneumoniae

Laboratory reports of Mycoplasma pneumoniae peak in a 3-4 year cycle in autumn and early winter. Transmission is by droplets and close contact is required. Infection rates are highest in children and young adults.

Respiratory Syncytial Virus (RSV)

Respiratory Syncytial Virus (RSV) is a major cause of bronchiolitis, and also causes tracheobronchitis and pneumonia. Incidence of the disease peaks in winter and early spring, and is most severe in young children, those born prematurely or with chronic cardiorespiratory disease, and the immunocompromised.

Last Updated: 10/07/2008

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