The child had other underlying medical problems according to the report but yet the parents were dragging the child across the country with the flu. It doesn’t sound as if they were too worried about the child or anyone else for that matter.
How many people did they infect in the process? Maybe they should have been seeking medical care for the child instead of ‘visiting’ family and friends across Mexico (and spreading the flu).
Underlying medical problems could be many different things: asthma, cancer, chicken pox, and who knows what else. Is there any evidence the parents knew the child had the flu prior to visiting relatives? Given my experiences with Mexican culture, the last things parents would do is knowingly endanger their child or other family members.