United States health officials recommend that women wait at least two months, and men at least six, before attempting to conceive after infection with the mosquito-borne Zika virus.
Zika has been linked to thousands of suspected cases of birth defects in Brazil.
The new guidance, issued by the US Centers for Disease Control and Prevention, followed earlier recommendations by the agency focusing on preventing infections in women who were already pregnant.
The conception guidelines were the agency's best guess based on limited available scientific evidence on how long Zika persists in blood or semen.
The virus was first detected in Brazil last year and spread rapidly through Latin America and the Caribbean.
Cases have also been recorded in parts of the Pacific, including Samoa and the Marshall Islands.
An expert on pregnancy and birth defects for the US agency, Denise Jamieson, said mounting evidence supports a link between Zika and microcephaly, a birth defect that is a sign of incomplete brain development and possibly other problems, such as miscarriage.
The World Health Organisation (WHO) declared Zika a global health emergency on 1 February.
Concern had been raised about a suspected link between the virus and two neurological disorders: microcephaly, which is associated with unusually small heads and, often, brain damage in infants; and, Guillain-Barré syndrome, in which the immune system attacks part of the nervous system.
Those links were yet to be confirmed, but the WHO said last week new research had strengthened the link between the virus and foetal abnormalities, and advised pregnant women to avoid travel to areas of ongoing Zika outbreaks.