Though Hurricane Matthew poses a threat to anyone in its way, certain populations are more vulnerable to its effects than others.

That’s because a hurricane’s human cost is determined as much by a community’s ability to react ­­–­ and bounce back – as by its wind velocity and the volume of rain it packs.

A multitude of social and environmental factors influence a community’s vulnerability to hurricanes and other emergencies.

These four top the list.

1. Mobility: In advance of Hurricane Matthew, Florida and the Carolinas have called on coastal communities to evacuate inland. For elderly residents and those without access to a car or other forms of transportation, compliance with evacuation orders can prove challenging. Geography can also present an obstacle. For example, islands in the Florida Keys are connected to the mainland by a series of bridges.

2. Poverty: Not everyone within a hurricane’s path is equally at risk. In fact, many of the locations most vulnerable to hurricanes are inland and in rural areas. A Direct Relief study looked at a decade of hurricane data and found the ten counties where people would likely be overwhelmed by a hurricane’s impact. None of the counties were coastal. One reason is that people living in coastal areas tend to be wealthier, better prepared, and able to evacuate quickly if needed. Inland areas may also suffer from flash flooding and mudslides.

3. Health: In emergency situations, people who depend on medications for chronic conditions – primarily diabetes, asthma, and hypertension – are particularly at risk if their medications are unavailable. People often leave their medication at home during mass evacuations. Also, power outages can compromise insulin or other supplies that require refrigeration.

4. Language: Language barriers can hinder all areas of emergency response. They can prevent residents from communicating with dispatchers and keep doctors from talking with patients in a triage tent.