Remove virus from wordpress site.

Good afternoon. You must remove the virus from the site on wordpress and give recommendations to avoid re-infection site.

Symptoms:

In the footer climbs (even after deletion) the virus that throws to other websites. At the same time in the header will change the logo of the website - they change on the original (ie, disappears the logo of the site, appears the logo of the template). While the footer is not displayed virus no.

The virus still appears on the website after 3-4 days.

Requirements: strict implementation DEADLINES.

Waiting for suggestions time and cost.