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Rationale for chemoprophylaxis for a single case

Risk to household contacts

About 97% of cases are sporadic53. Although the risk to contacts is low, the highest documented absolute and relative risk is to people who live in the same household as a case of meningococcal disease53,54. The Office for National Statistics defines a household as one person living alone or a group of people who share common housekeeping or a living room. The risk is highest in the first seven days after a case and falls rapidly during the following weeks53. If prophylaxis is not given, the absolute risk to an individual in the same household one to 30 days after an index case is about one in 30055,56,57. Beyond this four week period the risk is probably close to background levels53. The increased risk to household members may be due to a combination of genetic susceptibility in the family, increased exposure to virulent meningococci and environmental factors.

The case is likely to have acquired the invasive strain from a close contact, typically in the same household, who is an asymptomatic carrier58,59. The incubation period is usually three to five days3,11 and cases do not usually have detectable carriage until admission to hospital or shortly beforehand13. As the highest risk of illness in untreated households is observed in the first 48 hours after onset of disease in the index case54, the source of infection in these further cases is most likely to be from the same (or another) carrier and not from the case. It follows that transient contact with the index case before acute illness is unlikely to be an important risk factor for disease, so that mere proximity to the case (e.g. during travel in a plane, bus or car) may not justify prophylaxis. Guidance for the USA suggests that passengers seated next to the index case on a plane for more than eight hours should be offered prophylaxis, but only one possible transmission was detected in a recent review by ECDC. (Click here to see the guidance.) Low-level salivary contact should not be considered as a risk factor60. No cases have been reported following post-mortem contact with a case of meningococcal disease. Embalming is not considered a hazard for transmission61.

Aim of chemoprophylaxis

Chemoprophylaxis aims to reduce the risk of invasive disease by eradicating carriage in the group of close contacts at highest risk. It may act in two ways: (i) by eradicating carriage from established carriers who pose a risk of infection to others and (ii) by eradicating carriage in those who have newly acquired the invasive strain and who may themselves be at risk. The short- and medium-term reduction in risk among household contacts who are given antibiotics suggest that both mechanisms may operate55,56,62.

Taken from http://www.hpa.org.uk/webc/HPAwebFile/HPAweb_C/1194947389261

3. Chin J. Control of communicable disease manual. 17 ed. Washington: American Public HealthAssociation; 2000.

11. Boutet R, Stuart JM, Kaczmarski EB, Gray SJ, Jones DM, Andrews N. Risk of laboratory acquired meningococcal disease. J Hosp Infect 2001; 49: 282-4.

13. Edwards EA, Devine LF, Sengbusch CH, Ward HW. Immunological investigations of meningococcal disease. Scand J Infect Dis 1977; 9: 105-10.

53. Hastings L, Stuart J, Andrews N, Begg N. A retrospective survey of clusters of meningococcal disease in England and Wales, 1993-95: estimated risks of further cases in household and educational settings. Commun Dis Rep Rev 1997; 7(13): R195-R200.

54. De Wals P, Hertoghe L, Borlee-Grimee I, De Maeyer-Cleempoel S, Reginster-HaneuseG, Dachy A, et al. Meningococcal disease in Belgium. Secondary attack rate among household, day-care nursery and pre-elementary school contacts. J Infect1981; 3(Supp 1): 53-61.

55. Munford RS, De Taunay A, De Morais JS, Fraser DW, Feldman RA. Spread of meningococcalinfection within households. Lancet 1974; i: 1275-8.

56. Scholten R, Bijlmer HA, Dankert J, Valkenburg HA. Secondary cases of meningococcal disease in the Netherlands, 1989-90. A reappraisal of chemoprohylaxis. Ned Tijdschr Geneeskd 1993; 137:1505-8.

57. Meningococcal Disease Surveillance Group. Analysis of endemic meningococcal disease by serogroup and evaluation of chemoprophylaxis. J Infect Dis 1976; 134(2): 201-4.

58. Cartwright KAV, Stuart JM, Robinson PM. Meningococcal carriage in close contacts of cases.Epidemiol Infect 1991; 106: 133-41.

59. Kristiansen BE, Tveten Y, Jenkins A. Which contacts of patients with meningococcal disease carry the pathogenic strain of Neisseria meningitidis? A population based study. BMJ 1998; 317: 621-5.

60. Orr HJ, Gray SJ, Macdonald M, Stuart JM Saliva and meningococcal transmission, Emerg InfectDis 2003: 9(10):1314-5.

61. Controlling the risk of infection at work from human remains – a guide for those involved in funeral services (including embalmers) and those involved in exhumation. Health & Safety Executive 2005.

62. CDC. Exposure to patients with meningococcal disease on aircrafts – United States, 1999-2001. MMWR 2001; 50(23): 485-9.

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