Heilbrigðisskýrslur - 05.12.1982, Page 37

35
ENGLISH SUMMARY
In 1976 the World Health Organization encouraged its member
countries to conduct serological surveys in order to determine
swine influenza antibody levels in the population. In Iceland
the survey here described was carried out in the University
Department of Microbiology at the initiative of the Director of
the Icelandic Public Health Service. The aim was to determine,
if there were any significant differences in immunity levels in
those individuals infected in the influenza pandemic of 1918-'19
and those who were not infected. Furthermore the survey was
intended to be of assistance in selecting priority groups for
vaccination.
In Iceland the 1918-'19 pandemic came in three waves. In order
to prevent the spread of the second wave, which began in South-
Iceland, a strict quarantine was enforced and therefore the
Northern and Eastern districts of the island were spared (Fig 2) .
For this survey sera from 1405 individuals of various age and
place of residence were collected (Fig 2). The participants
answered a questionnaire concerning their places of residence,
past virus infections and vaccinations. Those who were born
before the great pandemic were grouped according to their place
of residence 1918 (Fig 9).
Hemagglutination-inhibition (HI) antibodies against A/New Jersey/
8/76 (HSwlNl), A/Victoria/3/75 (H3N2) and B/Hong Kong/5/72 (BXl-HP)
influenza virus strains were determined. Antigens were supplied
by WHO and their recommanded test methods used (15) .
The results of these studies are demonstrated in tables 3, 4 and
5, and in Fig 5, 6, 7, 8, 9, 10, 11, 12 and 13. The results
indicate higher HI antibody titres against A/New Jersey/8/76 in
individuals born before 1918 as compared with those born after 1918
(Table 3, Fig 6). A gradual fall in HI antibody levels was
detected in individuals born 1918-'30 (Fig 7). Individuals born
after 1930 have not significant antibody levels to A/New Jersey/
8/76 (Fig 6): Furthermore lower antibody titres were found in
those individuals living 1918 in the noninfected regions of Iceland
(Fig 9). Geometric mean of HI titers in sera from individuals
born b.efore 1918 was 65.0 in the infected areas and 33.9 in the
uninfected areas. Significantly different antibody levels to
A/Victoria/3/75 according to age were not found (Table 4, Fig 10).
Antibodies against B/Hong Kong/5/72 were found in high proportions
in all agegroups tested (Table 5, Fig 12).
The results show that the influenza epidemic of 1918 must have
been caused by a virus serologically similar to A/New Jersey/8/76
and that related strains caused influenza in the following decade
(Fig 7). The A/Victoria strain does not seem to have caused an
epidemic in Iceland before the survey, and older individuals are
comparatively at risk (Fig 10). The B strain seems to have caused
a recent infection (Fig 12), but no major outbreak of influenza B
had occured in Iceland since 1962.
Pigs are rare in Iceland and only few people exposed to them.
In this survey 40 pig sera were tested and did not have HI
antibodies against A/New Jersey/8/76.