Low but increasing levels of influenza activity in Europe:
an update from EISS, week 43
In the week ending 26 October 2003, Scotland reported local
to the European Influenza
Surveillance Scheme (EISS, www.eiss.org
(1). Sporadic but increasing influenza activity was reported in England, the
Republic of Ireland and Spain, although usual winter baseline incidence levels
were not exceeded. Sporadic activity and stable or decreasing clinical incidence
rates were reported in France and Portugal, and 11 networks reported no influenza
activity (that is, the overall level of clinical activity was at baseline
levels). The Czech Republic, England, Republic of Ireland, Scotland and Spain
all reported that clinical incidence rates were increasing compared with week
42/2003, and eight networks reported that they were stable.
Influenza A(H3N2) was the predominant virus circulating in France, Portugal
and Spain, and influenza A (unspecified) was predominant in England and
Ireland. Nine networks reported that there was no predominant virus circulating
in the population.
The total number of respiratory specimens collected by sentinel physicians
in Europe during week 42/2003 was 287. The percentage of specimens that
tested positive for influenza was 13%, ranging from 0% (in 10 networks)
to 40% (Republic of Ireland). Of the 37 positive specimens, 26 were cases
of influenza A(H3N2) and 11 were cases of influenza A (unsubtyped).
So far this season (weeks 40-43/2003), sentinel physicians participating
in EISS have collected 834 respiratory specimens and 98 have tested positive
for influenza (12%). All of the positive cases have been cases of influenza
A (55 cases of influenza A(H3N2) and 43 cases of influenza A (unsubtyped)).
The influenza B virus has not been detected in sentinel (or non-sentinel)
respiratory specimens so far this season.
EISS collects data on the cumulated number of sentinel and non-sentinel
virus isolates that have been characterised during the 2003-2004 season.
In week 43/2003, seven strain characterisations were reported to EISS and
all seven were the new drift variant A(H3N2)/Fujian/411/2002 (four in England
and three in the Republic of Ireland). Northern Ireland reported one case
with this strain variant in week 42/2003, and so eight cases of this new
drift variant have been reported to EISS so far this season, all from Great
Britain and Ireland.
The new drift variant A(H3N2)/Fujian/411/2002 was the predominant virus
circulating in Australia and New Zealand during the recent (southern hemisphere)
influenza season, and activity during this season was relatively high in
both countries (2). The A/Fujian-like viruses are related to the A/Panama-like
(H3N2) strain included in the current 2003-2004 vaccine (3,4) and antibodies
induced against this vaccine strain cross react with A/Fujian-like strains,
but generally to a reduced level (2). On the evidence available so far,
it is to be expected that the vaccine will also offer some cross protective
immunity to the drift variant A/Fujian-like viruses. Influenza vaccination
remains the most important intervention to limit influenza infection. Since
the vaccine is composed of A(H1), A(H3) and B strains (3,4), it also offers
protection against A(H1) and B viruses that might co-circulate with the
A(H3) viruses or become dominant. The spread of influenza virus strains
and their epidemiological impact in Europe will be carefully monitored by
EISS in collaboration with the World Health Organization Collaborating Centre
The EISS Weekly Electronic Bulletin presents and comments on influenza
activity in the 19 European countries (22 networks) that are members of
EISS. In week 43/2003, 17 networks reported clinical data and 14 networks
reported virological data to EISS. The bulletin with epidemiological and
virological data for week 44/2003 will be available on the EISS website
on 7 November.
*This indicates that increased influenza-like
illness activity was reported in local areas (for example, a city) within
a region of Scotland, or that outbreaks were reported in two or more institutions
within a region, with laboratory confirmed cases of influenza activity.
The levels of activity in remainder of the region, and other regions of
Scotland, remained at or below baseline levels during week 43.
Map. geographical spread of influenza and the intensity
of activity as assessed by each of the networks in EISS. Week 43 : 20/10/2003-26/10/2003.
Source: EISS. For an interactive version of this map, see reference 1
Dominant virus A
H1N1 = Dominant virus (H1N1)
H3N2 = Dominant virus (H3N2)
H1N2 = Dominant virus (H1N2)
B = Dominant virus B
A & B = Dominant virus A & B
= : stable clinical
+ : increasing clinical activity
- : decreasing clinical activity
= no evidence of influenza virus activity (clinical activity remains
at baseline levels)
Sporadic = isolated cases of laboratory
confirmed influenza infection
Local outbreak = increased influenza activity
in local areas (e.g. a city) within a region,
or outbreaks in two or more institutions (e.g. schools) within a region.
Regional activity = influenza activity
above baseline levels in one or more regions with
a population comprising less than 50% of the country's total population.
Widespread = influenza activity above baseline
levels in one or more regions with a population
comprising 50% or more of the country's population. Laboratory confirmed.