A mathematical model of common-cold epidemics on Tristan da Cunha

Records of seven common-cold outbreaks on the island of Tristan da Cunha are compared with the corresponding time courses given by the mathematical model of Kermack & McKendrick (1927) and with an alternative model that directly involves a constant average duration of individual infection. Using computer simulation techniques the latter model is shown to be preferred and is then closely matched to the field data to obtain values for the model parameters. Consideration is then given to the intensity of epidemics predicted by the model and to the distribution of the actual epidemics relative to the theoretical epidemic threshold.

Studies of respiratory viruses in personnel at an Antarctic base

Thirteen men wintering on an Antarctic base were isolated from other human contact for 10 months. During this period Coxsackievirus A21 and later influenza A2 virus were administered to some of the men. Serum samples were collected from each of the men at monthly intervals.Coxsackievirus A21 produced symptoms and apparently spread to uninoculated men. It also appears that repeated re-infections occurred and that the virus persisted in this small community for most of the period of isolation. HI antibody responses in the absence of neutralizing antibody responses seem to be transient.The vaccine strain of influenza virus induced antibody responses but did not cause symptoms. There was no evidence of spread to uninoculated men.Antibody titres against influenza C, parainfluenzaviruses 1 and 2 and coronavirus OC43 did not fall significantly during isolation.An outbreak of respiratory illness occurred at the end of isolation and its origin was traced. No causative agent was detected.

Common colds on Tristan da Cunha

Eight epidemics of respiratory disease have been observed among islanders of Tristan da Cunha. They seem to be initiated by the arrival of ships and transmission seemed to occur as a result of close human contact but could not always be traced. Islanders suffered from less colds than those in less isolated communities.

Viruses associated with acute respiratory infections in Royal Air Force personnel

All respiratory illnesses which were reported to the medical officers between September 1966 and December 1967 on a Royal Air Force station of 350 men were studied virologically.THREE PERIODS OF INCREASED RESPIRATORY INFECTIONS WERE OBSERVED: two occurred in the autumn, one in each year, and the third in the winter during January and February. The autumnal outbreaks were associated mainly with rhinovirus infections, and high isolation rates (82.1, 65.9%) were achieved at these times. Few of the illnesses during the winter outbreak could be diagnosed in the laboratory, and no evidence was found of infection with ;coronaviruses'.Despite the entrance of 30 fresh recruits direct from civilian life every 5 weeks, the respiratory infections encountered on the station were very similar to those in the local population and were not predominantly infections with adenoviruses, Coevirus, and Mycoplasma pneumoniae, as previously reported from larger military recruit centres.

A trial of chemoprophylaxis of natural influenza infection with U.K. 2371

In a five-week double-blind trial, 132 young adult volunteers received U.K. 2371, a synthetic isoquinoline derivative which had previously been shown to protect volunteers against challenge with certain influenza viruses. A comparable group of 130 volunteers received placebo. There was little difference between the groups in number or severity of acute respiratory illnesses during the trial or in the number of proven infections with influenza A2/Hong Kong/1968 virus. Tablet counts were carried out and single doses of isoniazid were used as a marker to confirm that the lack of prophylaxis was not the result of the failure of volunteers to ingest the tablets.

It is possible that the disparity between our results and those obtained in previous volunteer challenge studies may be due to differences in susceptibility of strains of influenza A virus to the isoquinoline drugs.

The epidemiology of the common cold. IV. The effect of weather

An investigation has been made of the association between weather and the numbers of colds reported on a given day. The seasonal trends were eliminated by working with the differences between the observed values on any day and the expected values derived from smooth curves fitted to the averages for the time of year.

Examination of nine weather variables for the day on which the colds were reported and for each of the 29 preceding days showed that only two, mean day temperature and water-vapour pressure at 9 a.m., were significantly correlated with the numbers of colds. Partial correlation studies showed that the strongest association was with lowered mean day temperature between 2 and 4 days before the reported onset of symptoms.

Regression analysis demonstrated that the magnitudes of the associations were sufficient to account for the greater part of the seasonal variation in the incidence of the common cold in both London and Newcastle. A small effect of atmospheric pollution appeared in this analysis.

These results suggest that some effect of low outdoor temperature promotes transmission of the virus or the development of disease.