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In Western countries , invasive infections caused by M1T1 serotype group A Streptococcus ( GAS ) are epidemiologically linked to mutations in the control of virulence regulatory 2 - component operon ( covRS ) .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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