Introduction: Measles have increased in incidence in some parts of the developed world in the past 10-15 years. They can be fatal and lead to severe sequelae.Measles were infrequently introduced to Iceland in the 19th century and consequently, epidemics were few but associated with an extremely high mortality.  The availability of 19th century church registries enables studies on the impact of measles on mortality. 

Materials and methods: Historical accounts mention two major measles epidemics, starting mid-year 1846 and 1882. We analysed these two epidemics using contemporary historical sources, mainly original church registries.  

Results: In the 1846 epidemic the data show a clear increase in mortality in June and reach a peak in July of 741 fatal cases total, a four-fold increase from expected baseline rate. The epidemic subsided in the ensuing five months. A cluster of measles was described in the eastern region of Iceland in 1869 but did not spread further. The epidemic of 1882 reached its peak in July, when 1084 individuals died, a five-fold increase from the expected rate. Excess mortality was highest in N-Isafjardarsysla county, 4,7 %, and none in A-Skaftafellssysla county where the illness was described 13 years previously. The highest numbers of fatal cases in the 1882 epidemic (64,6%) was among 0-4 year old children. The number of fatalities among women of child-bearing age was more than two-fold compared to men; the number of births 7-9 months following the 1882 peak dropped significantly by 50%.

Conclusions: This study highlights the consequences of measles following  introduction into a largely susceptible population and also documents the importance of herd immunity. Information can be identified on most individual fatalities during the 1846 and 1882 measles epidemics in Iceland.

Key words: Measles, mortality, epidemic, historical sources, pregnancy.

Correspondence: Magnús Gottfreðsson  magnusgo@landspitali.is

^{Sandra Gunnarsdottir1, Haraldur Briem1,2, Magnús Gottfredsson1,3
1}Faculty of medicine, University of Iceland, ²Directorate of Health, ³Landspítali University Hospital

Figures:

Figure 1. On the left there is a census from Snæfell and Hnappadalur deanery from the year 1846 written by Pétur Péturson former bishop. On the right there is a parish register of Landeyjaþing 1816-1848, BA/7 written by former priests Guðmundur Lassen and Jón Hjörtsson. Both are stored in the Museum of National Archives of Iceland.

Figure 2. Number of fatal cases by month in Iceland, 1845-1847

Figure 3. Mortality ratio by month in different regions of Iceland, 1846. The measles epidemic started close to Reykjavik in mid-year 1846 and subsequently spread to other parts of the country, peaking four months later in the most remote regions.

Figure 4. Excess mortality ratio in Iceland´s counties during the measles epidemics of  1846 and 1882. *In A-Skaftafellssýsla county there was no excess mortality.

Figure 5. Number of fatal cases by month in Iceland,  1881-1883.

Figure 6. Mortality ratio in different age groups among Icelanders 0-36 years of age who passed away in June, July and August, 1882.

Figure 7. The impact of measles epidemic in the year 1882 on the number of births the following year, 1883. The maroon coloured area shows the number of fatal cases in June 1882 to May 1883. The green line shows average number of births each month in the years 1877-1881 with 95% confidence interval. The red line shows the number of births from June 1882 to May 1883.