These symptoms also occur in other respiratory illnesses, such as influenza,
that are much more common than SARS. The feeling of shortness of breath often
does not begin until 3 to 7 days after the start of fever and the other symptoms.
However, this symptom in some individuals may progress quickly to extreme
shortness of breath and respiratory failure. This may require treatment with
oxygen or a ventilator (breathing machine). Elderly
persons or those with underlying illnesses such as diabetes or heart disease
are more likely to develop respiratory failure due to SARS, and they are more
likely to die from SARS if they become ill with the virus.