1) Paper-based centralised, scannable or manual entry forms: useful in developing settings or in places with no intention of becoming computerised.Example, a GP-based sentinel surveillance system.

Advantages: simple, quick, easy to use and interpret.

Disadvantages: time consuming, uses room, papers could be lost, quality of information could be doubtful and needs contrl by telephone or fax, obsolete.

2) Computerised stand-alone system: useful when the scope of the system is small and the size of the data set or the skills of the data manager are limited.

Example: a hospital-specific database on staff exposure to meningococcal meningitis and access to post-exposure prophylaxis.

Advantages: easy to maintain, information easy to process, easy to protect information.

Disadvantages: limited capacity and reduced opportunity for a comprehensive data base; need to keep back-ups in case of damage to the single computer, loss of confidentiality if kept in a network.