▁of ▁A IT ▁are ▁most ▁common ▁in ▁patients ▁with ▁prior ▁thy roid ▁disease ▁such ▁as ▁Hash im oto ' s ▁thy roid itis ▁or ▁thy roid ▁cancer . ▁ ▁The ▁most ▁common ▁cause ▁of ▁in fection ▁in ▁children ▁is ▁a ▁con gen ital ▁ab normal ity ▁such ▁as ▁p yr iform ▁sin us ▁f ist ula . ▁ ▁In ▁most ▁cases , ▁the ▁in fection ▁origin ates ▁in ▁the ▁pir iform ▁sin us ▁and ▁spread s ▁to ▁the ▁thy roid ▁via ▁the ▁f ist ula . ▁In ▁many ▁reported ▁cases ▁of ▁A IT ▁the ▁in fection ▁occurs ▁following ▁an ▁upper ▁resp ir atory ▁tract ▁in fection . ▁One ▁study ▁found ▁that ▁of ▁the ▁reported ▁cases ▁of ▁A IT , ▁ 6 6 % ▁occurred ▁after ▁an ▁ac ute ▁ill ness ▁involving ▁the ▁upper ▁resp ir atory ▁tract . ▁Although ▁the ▁rates ▁of ▁in fection ▁are ▁still ▁very ▁low , ▁cases ▁of ▁A IT ▁have ▁been ▁on ▁the ▁rise ▁in ▁recent ▁years ▁due ▁to ▁the ▁higher ▁occurrence ▁of ▁imm une - comp rom ised ▁patients . ▁ ▁Other ▁causes ▁of ▁A IT ▁are ▁commonly ▁due ▁to ▁cont am ination ▁from ▁an ▁outside ▁source ▁and ▁are ▁included ▁below . ▁Re pe ated ▁fine ▁need le ▁asp ir ates ▁Per for ation ▁of ▁es oph ag us ▁Regional ▁in fection ▁ ▁Di agn osis ▁Pat ients ▁who ▁are ▁sus pected ▁of ▁having ▁A IT ▁often ▁under go ▁tests ▁to ▁detect ▁for ▁elev ated ▁levels ▁of ▁white ▁blood ▁cells ▁as ▁well ▁as ▁an ▁ul tras ound ▁to