The child has a fever above 39°C — they need to get to the doctor immediately.
Tips
usage
发烧 (fāshāo) means 'to have a fever.' Adding 高 (gāo, high) intensifies it to 'high fever.' The verb phrase follows the 发 + illness pattern common in Chinese: 发烧, 发炎 (inflammation), 发冷 (chills).