▁adult s ▁are ▁stre pt oc oc cal . ▁The ▁number ▁of ▁ph ary ng itis ▁cases ▁is ▁higher ▁in ▁children ▁when ▁compared ▁with ▁adult s ▁due ▁to ▁expos ures ▁in ▁schools , ▁nur series , ▁and ▁as ▁a ▁consequence ▁of ▁lower ▁host ▁imm unity . ▁Such ▁cases ▁Stre pt oc oc cal ▁ph ary ng itis ▁occurs ▁more ▁frequently ▁from ▁December ▁to ▁April ▁( l ater ▁winter ▁to ▁early ▁spring ) ▁in ▁season al ▁countries , ▁possibly ▁due ▁to ▁changing ▁climate , ▁behaviour al ▁changes ▁or ▁pre dis pos ing ▁vir al ▁in fection . ▁D ise ase ▁cases ▁are ▁the ▁lowest ▁during ▁aut umn . ▁ ▁M T 1 ▁( met abol ic ▁type ▁ 1 ) ▁clone ▁is ▁frequently ▁associated ▁with ▁invas ive ▁Stre pt oc oc cus ▁py ogen es ▁in fe ctions ▁among ▁developed ▁countries . ▁The ▁inc idence ▁and ▁mort ality ▁of ▁S . ▁py ogn es ▁was ▁high ▁during ▁the ▁pre - pen ic ill in ▁era , ▁but ▁had ▁already ▁started ▁to ▁fall ▁prior ▁to ▁the ▁w ides p read ▁avail ability ▁of ▁pen ic ill in . ▁Therefore , ▁environmental ▁factors ▁do ▁play ▁a ▁role ▁in ▁the ▁S . ▁py ogen es ▁in fection . ▁Inc idence ▁of ▁S . ▁py ogen es ▁is ▁ 2 ▁to ▁ 4 ▁per ▁ 1 0 0 , 0 0 0 ▁population ▁in ▁developed ▁countries ▁and ▁ 1 2 ▁to ▁ 8 3 ▁per ▁ 1 0 0 , 0 0 0 ▁population ▁in ▁developing ▁countries .