that was first detected in Mexico 是修飾主語的定語從句。
was declared a global epidemic on June 11,2009, 這句話是謂語部分
所以這句話主幹就應該是：
The outbreak of swine flu （that was first detected in Mexico） was declared a global epidemic on june 11,2009.
that was first detected in Mexico 是修飾主語的定語從句。
was declared a global epidemic on June 11,2009, 這句話是謂語部分
所以這句話主幹就應該是：
The outbreak of swine flu （that was first detected in Mexico） was declared a global epidemic on june 11,2009.