[注意]甲型H1N1流感死亡病例均患有慢性病

The Centers for Disease Control (CDC) confirms that most new cases of H1N1 swine flu in the U.S. and Canada are being spread from person to person with no link to travel to Mexico.

Though the virus now spreads on a community level, the only deaths outside of Mexico have been in people with underlying conditions or other factors that may have made them more vulnerable to complications.

Every year seasonal flu kills thousands and thousands of people - most of them either very young, very old, or susceptible because of other conditions, usually immune system-related.

An eldery Albertan woman became the first suspected death linked to swine flu, though not much is known about her underlying health issues. Her name has not been released.

Miguel Tejada Vazquez, 2, and his family visited Houston from Mexico. He became ill while travelling and died in hospital on Monday, May 4. The young boy suffered from an autoimmune disorder called myasthenia gravis, which causes the immune system to attack and weaken muscles.

    via Medbroadcast: Myasthenia gravis is a serious condition, but not usually a life-threatening one. However, in severe cases, the chest muscles can become so weak that patients have trouble breathing on their own and may require a ventilator for a few days to a few weeks.

The second U.S. death was Judy Trunnell, 33, a Texas school teacher. She was pregnant and in a coma when she died. Her baby girl was born health via Cesarean section. Trunnell suffered from asthma and a pair of autoimmune conditions - rheumatoid arthritis and psoriasis - that may have put her in danger from a new or powerful infection.