Eurosurveillance - Volume 12, Issue 9, 01 September 2007

In this issue of Eurosurveillance, two articles report data about pertussis.

The elimination of measles by 2010 is part of the strategic plan for measles and congenital rubella infection in the European Region of the World Health Organization.

This report describes a cluster of linked cases of three adults and one infant in a family, spread across the United Kingdom (UK). The initial follow-up was of a 20-year-old student with clinical symptoms of pertussis. This diagnosis led to the discovery of two other unvaccinated adult family members with symptoms that fit the case definition for pertussis and a laboratory-confirmed tertiary case in an unvaccinated infant who had to be hospitalised. This report aims to act as a reminder for including pertussis as a differential diagnosis in patients with a long duration of respiratory symptoms and highlights the importance of rapidly identifying and managing close contacts of cases. This is key in protecting the most vulnerable - namely, infants - from infection.

The objective of this study was to describe the incidence (1982-2005) and epidemiologic characteristics of pertussis cases (1998-2005) in the Autonomous Region of Madrid using data drawn from the epidemiologic surveillance network and computerised hospital discharge data. In the 1990s, the trend in the pertussis incidence in the Autonomous Region of Madrid was clearly falling. The typical seasonal pattern of pertussis remained. A peak in incidence were observed in 2000, and another peak, 2.5 times higher, in 2003. They affected all age groups, but children under one year of age were the most frequent cases, followed by the five to nine year-olds. The greatest increase was seen in the age groups from 10 to 14 and from five to nine. Since 2002, the proportion of cases diagnosed serologically has increased. The incidence of hospital discharges among small children exceeded that of reported cases. More than half of the cases with known vaccination status had received at least three doses of vaccine. The upward trend observed since 2002 could be due to improved case detection, availability of serologic techniques, and a rise in the susceptible population aged five to 14 years. The fact that epidemic peaks continue to occur and that there is a seasonality to the disease seems to indicate that despite the vaccination programme the circulation of the bacteria has not been interrupted. The introduction of the acellular vaccine in 2000 does not appear to have played a significant role in the increase in disease incidence.

The infants of mothers with vaccine-induced immunity lose passive acquired measles antibodies earlier than infants of naturally infected mothers. This study included two cohorts of parturient women: one composed of women who gave birth in 1990 (end of the epidemic period), and another comprising women who gave birth in 2006 (after eight years without virus circulation). Immunoglobulin G (IgG) antibodies against measles (IgG-AM) were investigated by enzyme immunoassay in stored serum samples (-40°C). Measles-IgG titres of >400 mIU/mL were found in all 185 parturient women who gave birth in 1990, all with natural immunity. Of 185 women who gave birth in 2006, most of whom had vaccine-induced protection, measles-IgG were undetectable in 4.9% (<150mIU/mL), values were borderline in 7% (150-299 mIU/mL), and the geometric mean titre was lower (p<0.001), being 3.4 to 3.8 times lower in women aged <28 years. The changing levels of maternal measles antibodies suggest that in Spain, the window of susceptibility to measles in infants is increasing. To protect susceptible infants against measles in countries with long-established vaccination programs where measles immunity in parturient women was artificially acquired, it is essential to ensure that both doses of the routine measles vaccine achieve a coverage of >95%, and that infants receive the first vaccination dose before 15 months of age (e.g. at 12 months).

Influenza activity in Europe during the winter 2005-2006 started late January - early February 2006 and first occurred in the Netherlands, France, Greece and England. Subsequently, countries were affected in a random pattern across Europe and the period of influenza activity lasted till the end of April. In contrast to the winter seasons in the period 2001-2005, no west-east pattern was detected. In 12 out of 23 countries, the consultation rates for influenza-like illness or acute respiratory infection in the winter 2005-2006 were similar or higher than in the winter 2004-2005, despite a dominance of influenza B viruses that normally cause milder disease than influenza A viruses. In the remaining 11 countries the consultation rates were lower to much lower than in the winter 2004-2005. The highest consultation rates were usually observed among children aged 0-14. The circulating influenza virus types and subtypes were distributed heterogeneously across Europe. Although the figures for total virus detections in Europe indicated a predominance of influenza B virus (58% of all virus detections), in many countries influenza B virus was predominant only early in the winter, whilst later there was a marked increase in influenza A virus detections. Among the countries where influenza A viruses were co-dominant with B viruses (9/29) or were predominant (4/29), the dominant influenza A subtype was H3 in seven countries and H1 in four countries. The vast majority of characterised influenza B viruses (90%) were similar to the B/Victoria/2/87 lineage of influenza B viruses that re-emerged in Europe in the winter 2004-2005 but were not included in the vaccine for the influenza season 2005-2006. This might help to explain the dominance of influenza B viruses in many countries in Europe during the winter 2005-2006. The influenza A(H3) and A(H1) viruses were similar to the reference strains included in the 2005-2006 vaccine, A/California/7/2004 (H3N2) and A/New Caledonia/20/99 (H1N1), respectively. In conclusion, the 2005-2006 influenza epidemic in Europe was characterised by moderate clinical activity, a heterogeneous spread pattern across Europe, and a variable virus dominance by country, although an overall dominance of influenza B viruses that did not match the virus strain included in the vaccine was observed.

In 2005 there were 8.8 million new cases of tuberculosis (TB) globally and 1.6 million deaths. Incidence rates in Western Europe ranged between 4 and 10 per 100,000 in 2001, but TB is still a significant challenge in this region, especially due to delayed diagnosis and management. Prisons are a potential “breeding ground” for TB with a mean notification rate of 232 cases per 100,000 prisoners in Europe in 2002. This report describes the measures taken in response to a TB case in a British prison. Following diagnosis, the “stone in the pond” method was used to identify potential contacts. Selection criteria were agreed and screening tools included the Quantiferon test. These methods, combined with an effective integrated community and hospital TB service, resulted in the successful management of the incident.