Complex sentence: For sexually transmitted diseases, this is generally limited to sexual partners and can fall under the heading of partner services, but for highly virulent diseases such as Ebola and tuberculosis, a thorough contact tracing would require information regarding casual contacts.
Split into simpler sentences: For sexually transmitted diseases, this is generally limited to sexual partners and can fall under the heading of partner services. But, for highly virulent diseases such as Ebola and tuberculosis, a thorough contact tracing would require information regarding casual contacts.