Shoppers were polite but tense as they sought food, water and gasoline from stores where shelves were quickly emptied and pumps soon ran dry.

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When key workers fall ill or get afraid and low paid workers simply do not turn up for work food stores will have empty shelves, close and be looted, gas pumps will be dry and prescription drugs not delivered.

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Sao Paulo, Brazil (CNN) -- Gas pumps in Sao Paulo, Brazil's biggest city and financial capital, were running dry Wednesday due to a truckers strike that began two days ago.

CNN: Gas pumps near empty in Sao Paulo due to truckers strike