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Respiratory Infections

Weekly Report Articles

13 December 2016

Respiratory bacteria quarterly report. Quarter three: 1 July to 31 September 2016

The following report describes the most recent quarterly surveillance data on meningococcal disease, invasive pneumococcal disease and Haemophilus influenzae in Scotland. Information on the uptake of the routine childhood immunisations is published separately in the HPS Weekly Report. The latest report can be accessed at http://www.hps.scot.nhs.uk/ewr/redirect.aspx?id=70596.

Meningococcal disease

Meningococcal disease (MD) is a notifiable disease caused by infection with the bacterium Neisseria meningitidis. MD is a significant cause of morbidity and mortality in children and young people. Meningococcal Invasive Disease Augmented Surveillance (MIDAS - further details at http://www.hps.scot.nhs.uk/resp/surveillancesystems.aspx) was introduced in 1999 to monitor the impact of the meningococcal C vaccine and the data from this informs the following report.

Recent changes to the immunisation schedule

The meningococcal B (Men B) vaccine was introduced into the routine childhood vaccination programme on the 1 September 2015. All infants aged two months from this date (i.e. those born from 1 July 2015) will be offered the Men B vaccine at two, four and 12 months. The vaccine will be administered at the same time as the other routine childhood vaccinations received by infants at two, four and 12 months.

There was also a catch-up programme for infants born from 1 May 2015. Infants born before 1 May 2015 are not eligible to receive the Men B vaccine.

The Joint Committee on Vaccination and Immunisation (JCVI) (the UK advisory group on vaccination and immunisation) recommended a programme of vaccination with the MenACWY vaccine for 14-18 year olds to prevent the increase in the number of cases of meningococcal serogroup W. This phased programme ran in Scotland from August 2015 to March 2016. The vaccine was also offered to students under the age of 25 attending university for the first time from autumn 2015 (http://news.gov.scot/news/meningitis-b-added-to-routine-vaccinations).

Surveillance update

During the third quarter of 2016 (weeks 27-39), a provisional total of 20 cases of meningococcal disease were reported to MIDAS taking the total number of cases reported thus far in 2016 to 79. This is higher than the number reported during the same period in recent years (2012-2015 range 53-67 cases) (Figure 1). This increased number of cases has been observed in those aged under five years and those aged 25 years or older, while there has been a decrease in the number of cases aged 5-24 years. Meningococcal disease continues to occur more frequently in younger age groups: 36 cases (45.6%) were aged under five years, 11 cases (13.9%) were aged 5-24 years and 32 cases (40.5%) were aged 25 years and over (Figure 2).

Serogroups have been identified for almost all cases (72/79; 91.1%) reported in 2016: 38 were infected with serogroup B (52.8%), 17 with serogroup W (23.6%), 10 with serogroup C (13.9%), six with serogroup Y (8.3%) and one with serogroup E (1.4%). The remaining seven notifications were based on clinical diagnosis and no serogroup is likely to become available (Figure 3).

The number of serogroup B cases reported thus far in 2016 (38 cases) is higher than that reported in the same period of recent years (2012-2015 range 25-34 cases). Almost two thirds of serogroup B cases were aged under five years (24/38; 63.2%). The number of cases observed in this age group (n=24) is also an increase on that observed for the same time period last year (n=14). Six of these cases were born on or after 1 May 2015 and eligible for Men B vaccine. This compares with six cases for the birth cohort born the year before, suggesting that the overall increase for young children was not observed in those offered vaccination, in contrast to the overall increase in those aged under five years. Of cases eligible for vaccination, three cases had two doses of Men B vaccine, two cases had one dose of Men B vaccine and one case had no dose. All these cases were aged under 12 months, and so had not received a booster dose. Men B vaccine is not expected to protect against all serogroup B strains and further detailed microbiological testing is required in order to evaluate the full impact of Men B vaccine.

Serogroup W cases continue to be reported. However, since the introduction of the Men ACWY immunisation programme in summer 2015, there has been a steady decline in serogroup W cases in young adults (aged 15-24 years, Figure 4), potentially suggesting early effectiveness of the campaign. Thus far in 2016, 17 serogroup W cases have been reported, none of which were in young adults (aged 15-24 years). The majority (9/17 52.9%) of serogroup W cases were in adults aged 25 years and older and the remainder were in children under five years of age (8/17, 47.1%). This compares with fourteen cases (five cases were in under five years, seven cases were aged 5-24 years and two cases were aged 25 years and over) in the same time period in 2015 and three in the same time period in 2014, respectively.

Since the introduction of Men C vaccine, serogroup C cases declined and were rarely reported in Scotland. However, to the end of September 2016, ten cases have been reported which is more than the total number reported in 2015 (three cases). Six of the serogroup C cases were in older adults (not eligible for Men C vaccination), two cases were in immunised children (last dose more than 10 years ago) and two were in un-immunised children (aged under five years).

Information on clinical presentation was available for almost all meningococcal cases (78/79; 98.7%): 40 (51.3%) cases presenting with septicaemia, 25 (32.1%) with meningitis, 10 (12.8%) with both meningitis and septicaemia and three (3.8%) cases with other presentations (including necrotising fasciitis, peri-orbital cellulitis and epiglottitis). Thus far in 2016, six deaths from meningococcal disease have been reported to MIDAS representing a case fatality ratio of 7.6%. This is higher than that reported in the same time period of recent years (2.4% in 2012, 7.2% in 2013, 4.1% in 2014 and 7.0% in 2015). Two deaths were due to serogroup C, one serogroup B, one serogroup W, one serogroup Y and one case had a clinical diagnosis only. All deaths were amongst adult cases. The number of deaths reported by serogroup and case fatality ratio from 2002-2016 is shown in Figure 5.

Invasive pneumococcal disease (IPD)

Invasive pneumococcal disease (IPD) is caused by infection of a normally sterile site (e.g. blood, cerebrospinal fluid) with the bacterium Streptococcus pneumoniae. IPD is a major cause of morbidity and mortality. It particularly affects the very young, the elderly and those with impaired or absent immunity. Streptococcus pneumoniae Invasive Disease Enhanced Reporting (SPIDER - further details at http://www.hps.scot.nhs.uk/resp/surveillancesystems.aspx) was introduced in 1999.

Pneumococcal conjugate vaccine (PCV-7) was introduced into the routine childhood immunisation schedule in September 2006. In spring 2010, PCV-7 was replaced with PCV-13 to provide broader protection against more serotypes of S. pneumoniae. Both vaccines follow the same three-dose immunisation schedule at two and four months of age followed by a booster at 12-13 months. PCV-13 offers protection against the following 13 serotypes of S. pneumoniae; 1, 3, 4, 5, 14, 6A, 6B, 7F, 9V, 18C, 19A, 19F and 23F. To coincide with the introduction of PCV- 7, enhanced surveillance was established for paediatric cases under five years of age. Data from SPIDER informs the following report.

During the third quarter of 2016 (weeks 27-39), a provisional total of 88 cases of IPD were reported to SPIDER taking the total number of cases reported thus far in 2016 to 497. This is an increase in case numbers compared with the same period of the previous five years (range 320-460 cases) but is lower than 2005 (i.e. the year before the introduction of PCV7) when 563 cases were reported (Figure 6).

Information on cases reported in 2016 indicates that IPD continues to occur more frequently in older age groups: 231 (46.5%) cases were aged 65 years and older, 191 (38.4%) were aged 35-64 years, 29 (5.8%) were aged 15-34 years, 11 (2.2%) were aged 5-14 years and 35 (7.0%) were aged under five years (24 of whom were aged under two years - Figure 7).

IPD in children aged under five years

Of the IPD cases reported thus far in 2016, 35 were in children under five years of age and eligible for PCV13 vaccination. This is higher than the number of cases reported in this age group in the same period of the previous five years (range 17-29 cases) but lower than the number of cases in the same period of 2005 (i.e. before the introduction of PCV7) when 78 cases were reported. The serotypes detected in children aged under five years thus far in 2016 are shown in Table 1.

Enhanced surveillance questionnaires were returned for over eighty percent of cases aged under five years (23/27; 85.2%) reported thus far in 2016. The 23 cases presented with the following clinical presentations: septicaemia (eight cases), pneumonia (six cases), meningitis (five cases), meningitis and septicaemia (three cases) and empyema (one case). For four cases information on diagnosis was unavailable. While 20 cases are known to have been discharged alive, five cases were not yet discharged when the form was completed and two cases had an unknown outcome. No cases are known to have died.

Circulating serotypes of Streptococcus pneumoniae

Typing results were available for 79.3% (394/497) of cases reported thus far in 2016. The most common serotypes reported were serotypes 8 (63 cases), 3 (41 cases), 22F (37 cases), 12F (39 cases) and 9N (29 cases). A total of 77 cases (19.5%) were caused by serotypes included in PCV-13, of which 74 were in cases aged five years or older. Of the three vaccine serotype cases aged under five years, two were infected with serotype 3 (one not yet eligible for vaccination and one had two doses of vaccine) and one was infected with serotype 19A (unknown vaccination history).

Haemophilus influenzae

During the third quarter of 2016 (weeks 27-39), HPS received reports on 19 cases of invasive Haemophilus influenzae taking the total number of cases reported thus far in 2016 to 63. This is similar to the number of cases reported in recent years (2012-2015 range 19-45) (Figure 8). Of the 63 cases reported thus far in 2016, 53 (84.1%) cases were in adults aged over 30 years and ten (15.9%) were in those aged 16 or younger. Information on the clinical presentation was available for four paediatric cases, three presenting with bacteraemia and one with meningitis.

Thus far in 2016, 14 isolates (22.2%) were not sent for typing by diagnostic laboratories, two cases were type f, one type a, one type b, one type e and 44 were non-typeable, continuing the increasing trend in non-typeable isolates reported since 2003 (Figure 9). This compares with 13 isolates not sent for typing, four type f and 28 non-typeable in the same period in 2015. Figure 10 shows the laboratory reports of invasive Hib disease in Scotland from 1999 to 2016.

Of the 63 invasive cases reported thus far in 2016, 58 had H. influenzae isolated from blood, three from CSF and two from pleural fluid. None of the cases were known to have died, which is comparable to the same period of the previous five years (range 0-1 deaths).

Acknowledgements

The authors would like to thank the microbiologists, health protection teams, clinicians, nurses and other staff who assist in the submission of samples to SHLMPRL and in the completion of surveillance forms.

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