The World Health Organization states:
The majority of those who died were pregnant, had asthma, diabetes or other chronic diseases…
Moreover, extremely obese people are susceptible. As Bloomberg writes:
Scientists don’t yet know whether extremely overweight people get sicker because of associated conditions like heart disease and asthma, or whether the excess fat itself makes them more vulnerable.
The common thread in all of these conditions appears to me to be that swine flu killed people whose bodies were stressed – either by illness, extreme obesity or pregnancy. Pregnancy is a wonderful thing, but it is stressful to the mother’s body.
Handwashing, good nutrition, higher doses of Vitamin D, exercise, adequate sleep and stress relief techniques – if you don’t know any others, just breathe slowly and deeply for several minutes – can only help. Some also claim that certain probiotics can help prevent the flu (see also this).
This is not to say that proper medical precautions should not be taken or that medical treatment should not be sought. They should . . . but only to the extent that they cause more good than harm. For example, some vaccines are life savers, while others cause more deaths than they prevent (and see this).
Update: I spoke with a very smart doctor, who generally agreed with my analysis. However, she explained that a woman’s immune system is depressed during pregnancy (so that the mother’s immune system won’t reject the baby) and that seriously obese people tend to also have health problems, such as asthma or diabetes.