Table 2

 Number of people in the infectious mononucleosis cohort with MS (“observed number”), expected number, ratio of rates in the infectious mononucleosis cohort to those in the reference cohort, and 95% confidence intervals for the rate ratio

Virus infectionObserved number of MS in infectious mononucleosis cohortExpected number of MS in infectious mononucleosis cohort*Adjusted rate ratio†95% Confidence intervals
ICD codes for infectious mononucleosis: ICD7 093, ICD8 075, ICD9 075, ICD10 B27. ICD codes for multiple sclerosis: ICD7 345, ICD8 340, ICD9 340, ICD10 G35. Conditions used in reference cohort, with Office of Population, Censuses and Surveys code edition 4 for operations and ICD9 code for diagnosis (with equivalent codes used for other coding editions): appendicectomy (OPCS 441–444), tonsillectomy/adenoidectomy (230–236), squint (ICD9 378), otitis externa, otitis media (380–382), varicose veins (454), upper respiratory infections (460–466), deflected nasal septum, nasal polyp (470–471), impacted tooth and other disorders of teeth (520–521), inguinal hernia (550), ingrowing toenail and other diseases of nail (703), sebaceous cyst (706.2), internal derangement of knee (717), bunion (727.1), limb fracture (810–816, 823–826), dislocations, sprains and strains (830–839, 840–848), superficial injury and contusion (910–919, 920–924). *Based on the rates in the infectious mononucleosis cohort and reference cohort combined. †Adjusted for sex, age in five year bands, district of residence, and time period in single calendar years.
Multiple sclerosis after:
Infectious mononucleosis—all intervals62.82.170.79 to 4.77
    <1 year00.10.000 to 25.4
    1–4 years00.60.000 to 6.30
    5–9 years00.60.000 to 6.73
    10+ years61.54.011.48 to 8.93