household contacts:

All contacts living in the same household as the index case who have spent at least 4 hours/day on average or 20 hours/week with the case within 7 days of index case becoming ill and up to 24 hours after start of treatment of the index case

close contacts:

• Non-household persons who share the same bed with the case or had sexual relations with the case
• Persons who have had direct mucous membrane contact with the oral or nasal secretions of a case (e.g. mouth-to-mouth resuscitation, open mouth kissing) or direct contact with an open skin lesion of the case
• Injection drug users who have shared needles with the case
• Selected long-term care facility contacts
• Selected child care contacts
• Selected hospital contacts

who have been exposed to the case within 7 days of index case becoming ill and up to 24 hours after start of treatment of the index case.