Some people are more likely to have serious problems from H1N1 flu, including:
Pregnant women. The developing baby also is at risk for problems if the mother gets H1N1 flu.
People with long-term (chronic) health problems such as asthma or diabetes.
People with a weak immune system.
People who have serious heart or kidney disease or some diseases that affect nerves and muscles.
People younger than 25 years old.
Incubation and contagious periods
The time between getting infected with H1N1 virus and feeling sick (called the incubation period) is usually about 2 days but can be from 1 to 7 days.1 You can infect others starting 1 day before your symptoms start. And you may infect others up to 12 days after you get sick, although most people are infectious for about 6 days.1