IPA(key): [ɐbɐˈstrʲiɫəsʲ] <span class="searchmatch">обостри́лась</span> • (obostrílasʹ) feminine singular past indicative perfective of обостри́ться (obostrítʹsja)...
obostrílosʹ ― the situation has worsened [become aggravated] боле́знь <span class="searchmatch">обостри́лась</span> ― boléznʹ obostrílasʹ ― the condition has become acute/aggravated passive...