1. 表达谢意；2. 个人感受；3. 表达信心。
参考词汇：流行病epidemic 疫情 epidemic situation 新型冠状病毒 novel corona virus
Dear Medical workers，
I am Li Hua,a high middle school student in Shanxi. I'm writing to express sincere gratitude to you all for your devotion and sacrifice in this battle against the Novel Corona Virus.
In this epidemic, it is you who, despite the lack of equipment and the potential of infection, desperately rescue those infected but striving for life. It is also you who have shed new light on the virus with expertise to build up our confidence to defeat it. It is you who deserve all the admiration and love!
I can never express our thankfulness too much for your selfless contribution. It's widely believed that our joint efforts China will win the battle and make a quick recovery.
Good luck and stay well!