It can include emotional, physical, social or economic pressures.
Acute stress is the reaction to an immediate threat.
The threat can be any situation that is experienced as a danger. Common stressors include, noise, crowding, isolation, illness, hunger, danger and infection. Imagining a threat or remembering a dangerous event can also evoke a stress response. Modern life frequently results in on-going stressful situations. These may include difficult work or personal situations.