Heilbrigðisskýrslur - 01.12.1980, Page 133

The pattern of diffusion through the Icelandic community was a
distinctive one. The start to this wave was Siglufjarðar on the
north coast, with an introduction from Norway into the fishing port
of Siglufjörður. Within the next month, cases were being reported
both from other districts in the same part of the north coast, and
from Reykjavíkur and Vestmannaeyja in the south-west. Three separate
subsystems can be identified thereafter: (a) continued spread from
the original northern centre in the autumn of 1928 through the
remaining northern districts; (b) secondary spread from Reykjavíkur in
the early part of 1929 to other western and south-western districts;
and (c) spread between the eastern coastal districts in the winter
months of 1928. The provenance of the third subsystem is not clear,
but both Seyðisfjarðar and Norðfjarðar were reporting cases in October
1928, presumably stemming from the original Siglufjarðar introduction.
The vectors in Figure 2 show the movements of index cases (individuals
known to have measles) who transferred the disease from one district to
another. The diagram is based on the physicians' summary reports in
Heilbrigðisskýrslur. Similar diagrams were prepared for the book for
each of the sixteen waves. If we superimpose these for all waves, we
can construct a linkage map for measles spread over the last eighty
years (Figure 3). This gives the number of times measles are known
to have spread from place to place along the links shown in all
epidemics between 1896 and 1974. The upper illustrations indicate the
epidemic pathways between Reykjavíkur and other areas, while the
remaining pair shows the epidemic pathways between districts excluding
Reykjavíkur. For example, it can be seen from the top right-hand
diagram in Figure 3 that measles spread between Reykjavíkur and Akur-
eyrar, and between Reykjavíkur and ísafjarðar, in at least one quarter
of epidemics, but from the top left-hand diagram that it moved only
once between Reykjavíkur and ólafsvíkur.
The diagrams in Figure 3 make clear the central role of Reykjavíkur in
diffusing measles across Iceland. Strong bonds exist between Reykjavík
ur and the major regional districts of Isafjarðar, Akureyrar and Seyðis
fjarðar; but Figure 3 also makes clear the fact that any district is
at risk of infection from Reykjavíkur once the disease has arrived in
the capital. Superimposed upon this capital city dominance are local
diffusion cells centred around the main urban areas of Reykjavík, Isa-
fjörður, Akureyri and Seyðisfjörður (lower right illustration, Figure
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