Influenza
activity and influenza viruses
during the 2003-2004 epidemic season in Finland
Updated on June 3, 2004
First evidence of influenza virus circulation in Finland was obtained in September, when acute respiratory infections of three adults from a medium-sized town in Central Finland were confirmed serologically (diagnostic rise in HI antibody titre) to have been caused by H3 subtype virus. In October only sporadic cases of influenza were recorded, all of them by the Department of Virology, University of Turku.
A local influenza A virus outbreak began in the early November (week 45) among conscripts in a garrison in Central Finland; three first isolates characterized antigenically were confirmed as A/Fujian/411/2002-like. During week 47 some new local outbreaks due to H3 subtype virus were recorded and the first isolate was shown to possess HA1 haemagglutinin almost identical (four differentiating mutations) with the consensus sequence of A/Fujian/411/2002-like viruses isolated in Finland during the 2002/2003 epidemic season. The number of low-intensity local outbreaks increased further in the Finnish Defence Forces during week 48; a more intense outbreak was recorded at a military camp in Northern Finland. Increased epidemic activity was same time reported in some schools in Eastern Finland; otherwise the activity was presumably low in the general population.
During the first three weeks (49-51) of December a further increase in the number of laboratory-confirmed infections with influenza A were recorded throughout the country. Children and young adults were mainly affected. All subtyped strains were related to A/Fujian/411/2002, but some diversity was detected corresponding to the variability described in the WHO Influenza Centre, Mill Hill, London.
Lower numbers of diagnostic findings at the end of December and in the early January presumably were, at least in part, due to disruption of diagnostic services over the Christmas and New Year period. From week 3 onwards the decline is actual. Influenza activity remained at sporadic level in the country until a local outbreak caused by H3 subtype influenza A together with adenoviruses began early in February among conscripts in a garrison in the northern Finland. Thereafter only sporadic cases of influenza were recorded in Finland.
For weekly figures of laboratory-detected influenza viruses, see Table 1
Table 1: Diagnostic laboratory findings reported by
- Virological
laboratories associated with universities of Helsinki, Kuopio, Oulu and
Turku
- National Public Health
Institute, Helsinki
|
INFLUENZA ISOLATES AND DETECTION OF VIRAL ANTIGENS AND RNA |
|||||||||||
|
YEAR |
WEEK |
A* |
A H3 |
A H1 |
B |
YEAR |
WEEK |
A* |
A H3 |
A H1 |
B |
|
2003 |
35-39 |
0 |
0 |
0 |
0 |
2004 |
1 |
47 |
5 |
0 |
1 |
|
|
40 |
1 |
0 |
0 |
0 |
|
2 |
26 |
0 |
0 |
0 |
|
|
42 |
1 |
0 |
0 |
0 |
|
3 |
10 |
0 |
0 |
0 |
|
|
43 |
2 |
0 |
0 |
0 |
|
4 |
3 |
0 |
0 |
0 |
|
|
44 |
0 |
0 |
0 |
1 |
|
5 |
1 |
0 |
0 |
0 |
|
|
45 |
2 |
3 |
0 |
0 |
|
6 |
0 |
6 |
0 |
0 |
|
|
46 |
0 |
0 |
0 |
0 |
|
7 |
0 |
0 |
0 |
0 |
|
|
47 |
9 |
4 |
0 |
0 |
|
8 |
1 |
0 |
0 |
0 |
|
|
48 |
16 |
28 |
0 |
0 |
|
9 |
0 |
2 |
0 |
0 |
|
|
49 |
69 |
52 |
0 |
0 |
|
10-11 |
0 |
0 |
0 |
0 |
|
|
50 |
108 |
46 |
0 |
0 |
|
12 |
2 |
0 |
0 |
0 |
|
|
51 |
127 |
19 |
0 |
1 |
|
13-16 |
0 |
0 |
0 |
0 |
|
|
52 |
84 |
7 |
0 |
2 |
|
17 |
2 |
0 |
0 |
0 |
|
|
|
|
|
|
|
|
18 |
1 |
0 |
0 |
0 |
|
|
|
|
|
|
|
|
19-22 |
0 |
0 |
0 |
0 |
|
|
|
|
|
|
|
Total |
|
512 |
172 |
0 |
5 |
* Not studied for the subtype
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