W-135 meningococcal disease in a traveler: a case report

Emergence and disappearance of W135 meningococcal disease

W135 meningococcal disease was imported into Singapore in 2000 via Hajj pilgrims. Previous studies have showed sustained carriage of W135 with the potential for further transmission within communities. We therefore set out to determine whether W135 meningococcal disease would become endemic in Singapore after its introduction in 2000. Cases occurred until 2003, but no further cases have been reported since 2004.

Risk of transmitting meningococcal infection by transient contact on aircraft and other transport

Contact tracing of persons with meningococcal disease who have travelled on aeroplane or other multi-passenger transport is not consistent between countries. We searched the literature for clusters of meningococcal disease linked by transient contact on the same plane, train, bus or boat. We found reports of two clusters in children on the same school bus and one in passengers on the same plane. Cases within each of these three clusters were due to strains that were genetically indistinguishable. In the aeroplane cluster the only link between the two cases was through a single travel episode. The onset of illness (2 and 5 days after the flight) is consistent with infection from an unidentified carrier around the time of air travel. In contrast to the established risk of transmission from a case of tuberculosis, it is likely that the risk from a case of meningococcal disease to someone who is not identified as a close contact is exceedingly low. This should be considered in making international recommendations for passenger contact tracing after a case of meningococcal disease on a plane or other multi-passenger transport.

The 2003 SARS Outbreak In Singapore: Epidemiological and Clinical Features, Containment Measures, and Lessons Learned

On 6 March 2003, the Singapore Ministry of Health was notified of a cluster of atypical pneumonia in three patients with a history of travel to Hong Kong (Hsu et al., 2003). These three female travelers had stayed at the Metropole Hotel on the same floor as a Chinese physician later diagnosed with severe acute respiratory syndrome (SARS) (Hsu et al., 2003; Peiris et al., 2003). After returning to Singapore, one of the travelers (index A) who developed fever on February 25 was hospitalized at Tan Tock Seng Hospital on March 1, and was managed initially for straightforward community-acquired pneumonia. The other two travelers were also admitted with similar symptoms. Shortly thereafter, clusters of cases emerged in three separate wards, all traceable to the first imported case. By the time index A was isolated on March 6, she had already infected 22 persons, comprising ten health care workers, two inpatients, seven visitors, and three family members. One of the infected health care workers (index case B), with onset of symptoms on March 7 and a provisional diagnosis of dengue fever, was later admitted on March 10 to Ward 8A. At the ward she in turn infected 21 persons, including an inpatient with ischemic heart disease and diabetes mellitus, before she was isolated on March 13 (Wilder-Smith et al., 2004b). The inpatient (index case C) had been admitted on March 10 with fever, community-acquired pneumonia, and gramnegative bacteremia. When she developed heart failure on March 12, she was transferred to Ward 6A (the coronary care unit) and mechanically ventilated. However, she was isolated only on March 20 when SARS was suspected. By that time, 21 health care workers and 5 family members had become infected (Wilder- Smith et al., 2004b). A total of 109 cases were epidemiologically linked to index A. Intra-hospital transmission at Tan Tock Seng Hospital was interrupted by April 12, the date of onset of the hospital’s last case. Despite the institution of very rigorous infection control measures at Tan Tock Seng Hospital, SARS spread to four other health care institutions (Singapore General Hospital, National University Hospital, Changi General Hospital, and Orange Nursing Home – the last two are grouped together in Fig. 1 and a vegetable wholesale market (Gopalakrishna et al., 2004) (Fig. 1).

Meningococcal vaccine in travelers

PURPOSE OF REVIEW

New vaccines to prevent meningococcal disease have been licensed in recent years. It is therefore timely to discuss current vaccine strategies pertinent to international travelers in relation to the changing epidemiology.

RECENT FINDINGS

Serogroup W135 achieved epidemic status in Africa in 2002, and then largely disappeared over a short time period. The year 2006 saw a marked epidemic rise in meningitis attack rates across the meningitis belt in Africa. This rise was mainly due to a new serogroup A strain, indicating that a new meningitis epidemic wave is beginning in Africa. Epidemics are also spreading south of the meningitis belt, including the Greater Lakes Area (Burundi, Rwanda, Republic of Tanzania). The new quadrivalent conjugate meningococcal vaccine is now licensed in North America but not elsewhere. In most other industrialized countries, the serogroup C conjugate vaccine is licensed. Plain polysaccharide quadrivalent vaccines are available almost worldwide.

SUMMARY

Quadrivalent meningococcal vaccination is a visa requirement for Hajj and Umrah pilgrims to Saudi Arabia. Travelers to the meningitis belt during the dry season should be advised to receive meningococcal vaccine that covers all four serogroups. This recommendation should be extended to the Greater Lake Area, because of recent epidemics. Vaccine choices depend on availability.

Meningococcal disease in international travel: vaccine strategies

International travel and migration facilitate the rapid intercontinental spread of meningococcal disease. Serogroup A, and to a lesser extent serogroup C, have been responsible for pandemics in the past (mainly in Africa), but in recent years there was an international outbreak due to W135 related to the Hajj pilgrimage. The high carriage rates, persistence and transmissibility, in combination with the high case fatality rate of the Hajj-associated W135 outbreak clone, certainly raise considerable concern about the public health consequences of widespread dissemination of this organism and the potential for future epidemics. Indeed, the now evolving W135 epidemic in Africa mandates that the bivalent meningococcal vaccine should be replaced by the tetravalent meningococcal vaccine, covering A, C, Y and W135 serogroups. The currently available polysaccharide tetravalent meningococcal vaccine, albeit associated with high seroconversion and efficacy rates, has several shortcomings: it is not immunogenic in young children, duration of protective immunity is short, and it has minimal or no effect on nasopharyngeal carriage and therefore transmission of the organism. Immunogenicity of polysaccharide vaccines can be improved by chemical conjugation to a protein carrier, thereby eliciting a T-cell-dependent antibody response. In contrast to polysaccharide vaccines, conjugate vaccines are immunogenic in young infants, induce long-term protection, and reduce nasopharyngeal carriage. The tetravalent conjugate vaccine will be a leap forward in the control of meningococcal epidemics in affected countries. It will also boost the uptake of meningococcal vaccines in travelers, because the duration of protection is longer and it eliminates the problem of immune hyporesponsiveness of serogroup C with repeated dosing. The small risk of travel-associated disease for the general traveler and the unpredictable nature of epidemics make it difficult to provide evidence-based vaccine recommendations. The current recommendation is to vaccinate all Hajj pilgrims, travelers to areas with current outbreaks, travelers to the sub-Saharan meningitis belt, and high-risk individuals (i.e., those with immunodeficiencies).

Neisseria meningitidis W135, Turkey

We describe the first case of Neisseria meningitidis W135 meningitis in Turkey. The strain was genotypically unrelated to the clone (W)ET-37, isolated from Hajj pilgrims in 2000.