6.3.4. Respiratory tract infections
This section addresses influenza, tuberculosis,
legionellosis and SARS.
6.3.4.1.
Influenza
Seasonal influenza is an acute viral disease of the
respiratory tract, caused by influenza virus A and B. Each year there are
epidemics during the winter season, although sporadic cases do occur throughout
the year. Seasonal influenza poses a considerable public health threat.
The 2004–05 influenza season in Europe started in late
December 2004 with the first influenza activity occurring in the Northwest and
Southwest (Spain, United Kingdom and Ireland). The intensity of clinical
influenza activity in 10 out of 23 countries was higher than during the 2003–04
season, but lower or equal to the 2003–04 season in the other 13 countries. The
highest consultation rates were generally observed among children aged 0–14
years. In all, the peak consultation rates due to influenza-like illness or
acute respiratory infection were not especially high when compared with
historical data. The predominant virus strain was influenza A/H3N2, and similar
to the vaccine strain for the season. Influenza B viruses were co-circulating
with the A viruses during the whole influenza season in 11 out of 24 countries.
Seven of these were located in the North-East of Europe and in these countries
the proportion of B viruses was higher than in the rest of Europe. The seasonal
influenza strain of the 2004–05 and 2005–06 winter seasons was mainly of type
A/H3N2, just like in previous years, and both epidemics were of ‘medium’ size
in the EU.
Most EU Member States follow the WHO guidance that
recommends vaccination against human seasonal influenza be offered annually in
the early autumn for three major risk groups (the elderly, healthcare workers
and those with chronic medical conditions of all ages, such as diabetes or
heart disease). There is a WHO vaccination coverage target, accepted by all
European countries but this vaccine is currently underused in the EU. Some
countries cannot routinely monitor their coverage even for the elderly, and for
those that can, they are seemingly not meeting the WHO target. Therefore, there
still is a considerable potential for health gain in Europe not only through an
improved vaccination coverage in these selected groups, but also by adopting
other effective measures that minimise virus transmission. In this sense,
better application of the ECDC recommended personal protection measures
(regular hand-washing, good respiratory hygiene, mask-wearing in healthcare
settings during acute febrile periods, early isolation of symptomatic
personnel, etc.), would reduce the risk for all people.
The risk of an influenza pandemic
At irregular intervals new influenza A virus subtypes
emerge, leading to an influenza pandemic which may last for six to eight
months, and usually with a much higher disease and death rate than the seasonal
variety. It is impossible to predict which will be the next pandemic strain, or
when it will appear.
In recent years, a new strain of avian influenza (A/H5N1)
has spread globally among birds, and also occasionally infected humans. The
threat of avian influenza, and its potential for starting a human influenza
pandemic was a main concern in 2005. Starting in late summer, the avian
influenza virus A/H5N1 was detected in birds ever closer to Europe, with human
cases as close as Turkey, but no human cases in Europe. This virus in its
present form is poorly adapted to humans, and therefore, the human health issue
is minor as long as the A/H5N1 virus stays in its current form. The risk of
infection is almost entirely confined to people who own domestic poultry and
have close and intense contact with sick birds or their droppings. However,
they can protect themselves by applying the measures recommended by ECDC.
People travelling to countries where A/H5N1 is prevalent can sometimes enter
this category if they are staying with families with domestic poultry.
Since 2005 there has been an extraordinary concerted
effort by all EU countries to strengthen their readiness for a pandemic. However,
much remains to be done and it is believed that another two to three years of
intense work is required by all Member States as well as EU institutions to
reach an acceptable level of preparedness.
Key areas where further work is especially needed are:
·
integrated
planning across governments;
·
making
plans operational at local level;
·
inter-sectoral
operability at national level;
·
stepping
up prevention efforts against seasonal influenza;
·
extending
influenza research;
·
improving
EU influenza laboratory capacity.
6.3.4.2.
Tuberculosis
TB is a bacterial disease, caused by inhaling a bacteria
belonging to the Mycobacterium tuberculosis complex in droplets produced by
another person with pulmonary disease, and less frequently through the
ingestion of contaminated milk or through laboratory contamination. Only 10% of
people infected develop active TB. HIV infection increases the likelihood of
progression, while preventive therapy reduces this risk. The BCG vaccine may be
effective in limiting severe disease in childhood, but has no effect on
transmission. Therefore, TB control relies mainly on the detection of
infectious patients and treatment for at least six months with a combination of
antibiotics. Inadequate treatment may result in failure of cure, early relapse
or the development of drug-resistant disease (see section on antimicrobial
resistance, above).
In the early ’90s, a number of EU countries experienced an
increase or stabilisation in their TB notification rates. Subsequently, rates
declined in most countries and have reached very low levels in recent years.
This is the result of the sustained efforts of public health authorities. In
many EU countries TB is becoming a rare disease and many Member States are
heading towards elimination. In the Baltic States rates increased in the late
1990s, but have similarly decreased since 2002. In Sweden and the United Kingdom, however, overall rates increased substantially between 2001
and 2005, largely as a result of TB in immigrants. With the exception of the
Baltic States, Hungary, Poland and Portugal, rates have remained below 20 per
100 000 per year since 2001 in all countries.
The EU countries today fall into three broad patterns with
respect to TB:
·
Industrialised
countries with Westernised economies where TB rates are low and disease
increasingly aggregates in sub-populations and settings associated with poverty
and lowered immunity. Prevalence of HIV and drug-resistance among TB cases is
low to moderate.
·
The Baltic States, characterised by high TB rates, low migrant TB and high frequency of drug
resistance and where HIV is low but steadily increasing among TB patients.
·
Countries
in central Europe which joined the EU in 2004, where TB rates are moderate,
cases of foreign origin rare, and levels of HIV and drug resistance low.
In 2005, the 25 EU countries plus Iceland and Norway reported 59 497 TB cases corresponding to an overall rate of 13 per
100 000 per year, with a countrywide range from four to 75. Five countries
(France, Germany, Poland, Spain and United Kingdom) had more than 5 000
cases each, accounting for 62% of all cases reported. With the EU expansion in
2007, Romania will be the country with the highest notification rate (135 per
100 000 per year in 2005) and will effectively increase total
notifications in the EU27 by one half.
Risk factors
Recent demographic, political and socioeconomic changes in
Europe, such as the increased immigration and the upheaval that followed the
collapse of the former Soviet Union leading to a poorer control of the disease,
have been major determinants of the tuberculosis situation in Europe. Trends
show a continuous decline, at least in the western countries, but the general
pattern has changed. In the EU, TB is most prevalent in migrants coming from
high-prevalence countries outside the EU, the homeless, prisoners and drug
users.
TB is more common in males (male to female ratio, 1.7:1).
Cases aged over 64 accounted for 22% of the cases overall, while children under
14 represented 4%. Mean age is lower in western countries like Denmark, the
Netherlands, Sweden and United Kingdom, where foreign-born individuals nowadays
represent the majority of notified cases. In people of foreign origin, TB
concentrates in young adulthood, while, in the indigenous population, rates
increase slowly with age and are the highest in the elderly. Cases of foreign
origin accounted for 30% of all cases reported in the 25 countries (range
0–78%). Most cases of foreign origin were from Africa, Asia or from other
countries within the European Region itself. In countries with higher overall
rates, the proportion of foreigners was lower in general, suggesting that local
transmission was relatively important.
In the EU in 2005, 22% of AIDS cases had TB as the initial
AIDS-indicator illness. The contribution of HIV to the TB caseload differs
between countries. While 15% of TB cases in Portugal were HIV positive, the
co-prevalence was much lower in other countries with data. However, a doubling
in prevalence was registered in the UK in 2000–03 (from 4.2% to 8.3%) associated
with recent migration. HIV prevalence among TB cases has also increased since 2000 in Estonia and Latvia, reaching 6.4% and 3.5%, respectively in 2005.
Control tools and policies
In the coming years there is a need to improve
surveillance on risk groups and drug resistance and to better link laboratory
results with epidemiological surveillance data. The overall decline in
incidence also implies that several of the countries that still have a
programme for general BCG vaccination of children could consider switching to
vaccination of high-risk groups. Since the vaccine is not without adverse
effects, there is a break point where the number of serious adverse reactions
outweighs the few infections prevented.
Guidance on interventions for specific risk groups,
including guidelines for prevention and control of TB in immigrants, needs to
be promoted.
6.3.4.3.
Legionnaires’ disease (legionellosis)
Legionnaires’ disease is a respiratory disease caused by
the bacteria Legionella pneumophila, which can give severe pneumonia with high case
fatality rates, especially among elderly (figure 6.4) and immuno-compromised
individuals. Sporadic cases and outbreaks occur worldwide. The most common mode
of transmission is airborne and the reservoirs are aquatic systems such as
cooling towers, evaporative condensers, humidifiers, decorative fountains, etc.
Legionellosis can usually be treated effectively with antibiotics.
Figure 6.4. Trends of legionellosis
1995 - 2004.
The incidence of legionellosis increased between 1996 and 2002 in the EU. Since 2002, the incidence has remained stable at around one per 100 000 per
year. In 2005, a total of 4 189 human legionellosis cases were reported by
23 countries. The highest incidence of 3.36 per 100 000 per year was seen
in Spain, followed by Iceland with 2.38 per 100 000 per year. In 2005, 746
cases of travel-associated Legionnaires’ disease with onset in 2005 were
reported to the EWGLINET surveillance scheme by 15 Member States, Iceland and
Norway. Ninety-three new clusters were identified. Prophylactic measures
include regular cleaning and maintenance of the various water systems.
Guidelines for water plants sanitation have been prepared by EWGLINET experts.
6.3.4.4. Severe
acute respiratory syndrome (SARS)
SARS is a viral respiratory illness with a high fatality
rate, caused by a corona virus, the SARS-associated corona virus (SARS-CoV).
The main way that SARS seems to spread is by close person-to-person contact,
through respiratory droplets produced when an infected person coughs or
sneezes.
SARS was first recognised as a global threat in mid-March 2003 in East Asia. By July 2003, the international spread of SARS-CoV had resulted in 8 098 SARS
cases in 26 countries, with 774 deaths. In addition to the direct impact on
health services, the epidemic caused significant social and economic disruption
in areas with sustained local transmission of SARS and in the international
travel industry. Although sporadic imported cases of SARS also appeared in
Europe in 2005, the EU was largely spared from the infection. No SARS cases
were reported in the world in 2005.
Today, the most likely sources of infection with SARS-CoV
would be exposure in laboratories where the virus is used or stored for
diagnostic and research purposes, or from animal reservoirs of SARS-CoV-like
viruses. It remains very difficult to predict when or whether SARS will
re-emerge in epidemic form. The resurgence of SARS leading to an outbreak remains
a distinct possibility, and in the inter-epidemic period, all countries must
remain vigilant for its recurrence and maintain their capacity to detect and
respond to the re-emergence of SARS should it occur.
