INFLUENZA A (H3N2) - NORTHERN HEMISPHERE
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Influenza A/H3N2 Epidemic Continues In Northern Hemisphere
----------------------------------------------------------
With an early start, influenza activity associated with influenza
A(H3N2) viruses is being observed increasing significantly in some
countries in Europe (France, Norway, Spain and Portugal) and North
America (the USA). In Canada and the UK, weekly reported influenza
activity has slightly declined but the trend remains unclear.
This season, respiratory deaths occurring young children have been
reported in Canada, the UK, and the USA, with 6 deaths in children in
the UK confirmed to be in association with A/Fujian/411/2002-like
virus. However according to the data from the Office for National
Statistics in the UK, total respiratory deaths in young children are
within expected levels to this point of the year.
Most influenza outbreaks this season are attributed to influenza
A(H3N2) virus. Most viruses antigenically characterized so far have
been confirmed to be A/Fujian/411/2002-like, and the rest are
A/Panama/2007/99-like. Sporadic cases of A(H1) and B have also been
detected in some countries in the world.
******
[2]
Date: Sat 6 Dec 2003
From: ProMED-mail <promed@promedmail.org>
Source: UK Department of Health, CDR Weekly, Vol 13 no 49 , Thu 4 Dec
2003 [edited]
<
http://www.hpa.org.uk/cdr>
Influenza in the UK
-------------------
The early season increase in influenza activity in the United Kingdom
(UK) appears now to have levelled off. Consultation rates for
influenza-like illness in week 48 show little change from those seen
in week 47 in England, and continue to fall in Scotland and Northern
Ireland. In Wales, the rate is still rising but remains below the
baseline level. Consultation rates for influenza-like illness remain
highest in young children and have continued to increase. Whether
influenza activity will decline over the next few weeks or increase
again cannot be predicted. In north America and western Europe the
situation has been similar to that in the UK, with early activity and
the major circulating viral strain being the influenza A H3N2 Fujian
strain.
Deaths associated with influenza
--------------------------------
The Office for National Statistics (ONS) has reported a small
increase in the weekly number of deaths registered from all causes.
This is above the average number expected for this time of year
(i.e., weeks 45 to 47). The increase is not sufficiently large or
sustained, so far, to be considered a significant departure from the
normal range. The increase has occurred predominantly in the elderly
and is mainly attributable to respiratory causes.
A number of deaths in children and infants aged under 14 years) and
young adults have been reported to be associated with influenza
infections. At least 12 of the deaths in children (in England and
Scotland) have been shown to be due to influenza A infection, (7
confirmed as A H3 viruses, 5 of which have been confirmed to be of
the Fujian strain). The increased general practitioner consultation
rates for influenza-like illness in children may reflect increased
susceptibility in younger age groups. A high proportion of children
may be immunologically naive because of low levels of influenza
activity in recent years. If this interpretation is correct, many
children who are becoming sick are experiencing their primary
influenza illness, and it is to be expected that some will become ill
enough to require hospital care and some, unfortunately, will die.
The risk of severe illness is increased, but not confined to those
with underlying chronic illnesses. The A H3N2 subtype of influenza is
usually associated with higher morbidity and mortality in all age
groups than the other circulating types or subtypes of influenza.
******
[3]
Date: Sat 6 Dec 2003
From: ProMED-mail <promed@promedmail.org>
Source: UK Department of Health, Joint Committee on Vaccination and
Immunisation, Influenza Panel Meeting, Mon 10 Nov 2003 [edited]
<
http://www.doh.gov.uk/jcvi/mins10nov03.htm>
Likely Severity of Influenza This Year
--------------------------------------
The current level of new GP consultations for influenza-like illness
stood at 46 per 100 000 of the population for week 43. To put this in
context this was higher than at the same period for the last 3 years
but still within the previously accepted baseline activity. In
Scotland the rate was 56/100 000 and Northern Ireland 95/100 000. In
Scotland this is just above baseline level, but within the normal
expected range for the influenza season. Although highest in children
and young adults all age groups were affected.
3 school outbreaks had occurred in the Republic of Ireland (one with
high attack and hospitalisation rates) and schools had been affected
in Scotland. Scotland and Northern Ireland had seen severe prolonged
illness in a number of children, and deaths had occurred in children
(3 in Scotland and 2 in England).
All 5 deaths had been typed as the A/H3 Fujian-like strain.
In England A/H3 strains of influenza had been detected in 32 hospital
samples mainly in the under 5 age group. 9 of these had been typed; 6
were Fujian and 3 Panama-like strains. 30 H3 samples had come from
the community (mainly 15-44 age group).
Northern Ireland had 21 confirmed A/H3 samples 13 of which were
hospitalised; Wales had no A/H3 isolates so far.
Australia, New Zealand and Argentina had widespread A/H3N2 activity
during their winter -- predominantly the Fujian like-strain --
including outbreaks, which in Australia amounted to the highest level
of influenzafor 5 years. However, this came against a background of
low levels in the last few years, so as flu goes it was not
considered to have been exceptionally severe.
The rise in influenza activity this year is relatively early, however
it is not possible to predict the likely magnitude of the peak on
currently available data. The UK has had 2 or 3 years of low
influenza activity; the apparent level of activity this year is not
high in the context of our influenza experience over the last decade.
In summary, the incidence of influenza has started to rise steadily
earlier than in recent years. Most strains isolated have been A/H3
strains with no B and very little respiratory syncytial virus; young
children and young adults in the community have been more affected
than other age groups and there have been some reported outbreaks in
schools. There have been deaths in children, but not beyond what
might be expected at this stage of a flu season.
Likely efficacy of the vaccine
------------------------------
Influenza vaccine is made to the specification recommended by the
World Health Organisation. Antibodies from people immunised with the
current vaccine containing the Panama strain do cross react with the
new drifted variant Fujian-like strain. It is also important to
remember that the Panama strain is only one of 3 components to the
vaccine.
Also clinical experience so far does not point to the vaccine being
ineffective. It is therefore correct to say at this stage that the
vaccine gives some protection, and at the least should ameliorate
illness due to the variant strain.
The current situation is not without precedent. Review of the
literature revealed a previous influenza A (H3N2) outbreak in Japan
in 1992/93 season where the circulating virus had "drifted" from the
vaccine strain. Nevertheless, the vaccine was found to be effective
in preventing influenza in asthmatic children, a high risk group.
In summary, it was agreed that the vaccine should give good
protection against the virus strains in the vaccine it is also likely
to give significant if not complete, protection against the new H3N2
strain. It is the best protection for those aged 65 and over and in
at risk groups.
Illness in children
-------------------
Current epidemiology shows that those in the 0-4 and 15-44 year age
groups have been most affected by influenza.
Rates of serious illness and complications from influenza are much
higher in 'high risk' children than otherwise healthy children, but
considering the small proportion of children who fall into a risk
group and the large majority that do not, it is not surprising to see
some deaths in seemingly otherwise healthy children before seeing any
in a child in a risk group. So far this year, total respiratory
deaths in young children are within expected levels.
The group concluded that the current level of reported deaths in
children was not unexpected but the situation should be monitored
closely.
Policy for immunising children
------------------------------
The policy in the UK is to offer influenza vaccination to all
children aged over 6 months in an at-risk group. Immunisation is
relatively ineffective in younger children. The uptake in these
groups, from available records, appears low, however, and efforts
should be made to improve this. (Currently, monitoring of influenza
vaccine uptake is only carried out in the 65 and over age group.)
In the United States, a wider recommendation is made, but it is not
publicly funded, and uptake in children even in the risk groups is
estimated to be less than 10 percent.
Reviewing all available information the policy of immunising high
risk infants and children aged over 6 months is correct. None of the
evidence reviewed suggests this advice would have been different if
reviewed before this year's influenza season started.
Future policy development
------------------------
While first priority should be better implementation of current
policy in high-risk groups, the work already started on burden of
disease in other age groups (adults and children) and the
cost-effectiveness of immunising them as part of a public programme
should be progressed and options developed.
A particular difficulty arises from the lead time required to mount
vaccine production. Firstly knowledge of appropriate strains may be
lacking, and secondly manufacturers require fore knowledge of likely
vaccine needs -- irrespective of strain -- if they are to meet
demand. It follows that manufacturers need to know total dose
requirements as soon as possible, and then the strains to be
incorporated.
A cold-adapted live attenuated intranasal vaccine is licensed in the
United States, for otherwise healthy children over the age of 5 and
healthy adults under the age of 49 years only. It is not to be
licensed in Europe. The timetable for introduction of the intranasal
vaccine planned for the European market is as yet unclear. The Panel
will keep this under review.
Immunisation should be seen within the wider context of prevention
and control measures against influenza.
Summary
-------
Clinical indicators of influenza activity continue to rise in the UK
with the highest rates in the 0-4 year age group, and in the North.
Influenza A viruses are being isolated from community and
hospitalised patients. Of the viruses analysed so far at the National
Influenza Reference Laboratory most have been influenza A (H3N2)
Fujian-like strains which represent a 'drifted' variant of the H3N2
(Panama) strain included in this year's vaccine. The remaining
isolations have been of the H3N2 (Panama) strain. The Group agreed
that the current vaccine is expected to offer some cross-protection
against the Fujian-like strain and should give good protection
against the virus strains in the vaccine.
--
ProMED-mail
<promed@promedmail.org>
[The 3rd part of this post, although some days old, is reproduced
because it addresses many of the queries that have been directed to
ProMED-mail in recent days by correspondents in North America, where
the current outbreak is possibly more severe and causing greater
apprehension. - Mod.CP]
[see also:
Influenza A virus, vaccine composition 20031119.2871]
..................cp/pg/lm
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