2 sentences

1. 早期预警信号是哮喘发作前或刚开始时发生的变化。

   zǎo​qī yù​jǐng xìn​hào shì xiào​chuǎn fā​zuò qián huò gāng kāi​shǐ shí fā​shēng de biàn​huà.

   Early warning signs are changes that happen just before or at the very beginning of an asthma attack.

   Source: CCMatrix

2. 这些早期预警信号可逐渐发展，因此可能不会立即引起注意。

   zhè​xiē zǎo​qī yù​jǐng xìn​hào kě zhú​jiàn fā​zhǎn, yīn​cǐ kě​néng bù​huì lì​jí yǐn​qǐ zhù​yì.

   These early warning signs can develop gradually so they may not be immediately noticeable.

   Source: CCMatrix