Before 1992 orienteering sickness referred to jaundice. In the Swedish Wikipedia we find the following:
The first major disease outbreak among orienteers in Sweden occurred around 1960 in a disease that came to be known as the "orienteer disease" or "oriental jaundice" and was caused by hepatitis B. It also included Norway.  In Sweden, the first known disease cases occurred in 1958 and during the summer of 1959. Disease cases occurred in the Gothenburg area, Halland, Västergötland and Värmland. Already during the fall, diseases spread across southern Sweden and later even north.  A total of at least 600 known cases of illness are reported, but since a large number of infected people receive so-called subclinical disease, that is, undergoing the acute phase of the disease without striking symptoms, the number is estimated to have been greater. How many who died directly from the disease or from its late complications several years later is not known because follow-up could not take place. Several had their orienteering career broken because of the illness that takes a long time to heal.
On February 12, 1962, the then Swedish Orienteering Association issued an injunction, including, among other things, a prohibition on competition during the first half of 1962; special race costume from July 1 and that running water with good drainage would be at the target for washing. The injunctions had a good effect and from the second half of 1962 until the first half of 1965 there were few new cases of illness. In 1965, the requirement for competition costume was eased and in the spring of 1965-66, 84 informants fell ill.  When the injunction for covering race costume became strict again, the disease disappeared among orienteers in Sweden and has not returned.
In1992, a Swedish elite orienteer died during a training run shortly after returning home from a national team training camp in USA. During the previous few years a number of elite orienteers had died similar sudden deaths. This 1992 death received a lot of publicity and the Swedish Orienteering Association decided that something must be done, as it appeared that some sort of virus with a deadly outcome was circulating. The association cancelled all elite competitions for the coming 6 months and issued strong recommendations that orienteers should stop training or at least cut back significantly and not have any club training sessions where they could spread the sickness.
I immediately applied for money to do some research into how orienteers would cope with this situation and the stress it would probably cause. From my own knowledge of orienteering culture and theoretical considerations, I thought that many orienteers would not follow the recommendations and I was therefore particularly interested in why they didn't. (It is still unknown what the cause of the deaths were but it suspected that the bacteria Bartonella was the cause.)
Following is an abstract of my thesis based on my study.
In order to monitor responses to a series of sudden deaths among young elite orienteers in Sweden (1979-92) and related actions taken by the Swedish Orienteering Federation (SOFT), a longitudinal questionnaire study was carried out. In a series of four questionnaires over a 2-year period, a stratified sample of 406 orienteers were asked questions concerning their training, their attitudes about orienteering in general, SOFT’s recommendations, their discussions concerning the above deaths, and a variety of other things. The three strata in the sample included: an elite group, a relatively highly ranked group, and a group of recreational orienteers. The present paper relates the importance of the orienteering life-world, the amount of anxiety experienced, beliefs in causes of deaths, and changes/non-changes in training to one another. Drawing in particular on Festinger’s cognitive dissonance theory and Inglehart’s extension of it, it is shown that the orienteers behaved as could be expected. While very few individuals stopped training, many appear to have reduced training to some degree for a period of time. The initial degree of anxiety was greatest amongst females, but over time the main difference that remained was between recreational orienteers and the competitive ones.
It is argued that coping and stress are part of the anthropological condition of man and that every situation of conscious or unconscious choice is part of this process. Therefore the patterns of behaviour of humans in “critical” situations are best understood from an everyday life-world perspective. Some implications as to the analysis of intricate situations, what must be taken into account if proposed changes are to be successfully carried out, and the central role of the school in modern pluralistic society are discussed.
Here is the complete text of COPING WITH STRESS: Sudden death among orienteers