Apologies - I seem to have missed this essay. Anyway, I hope these comments help you or some other writers.
Your essay is very well written and 'most sentences are error free.' Have a look at the IELTS descriptors for this phrase.
Your essay is 356 words long, which is definitely on the long side. A lot of phrases could be removed and sentences shortened. You have a lot of long sentences and an average of 20.9 words per sentence (See the readability links at the top of this page under ‘Useful Links’). You need to try to reduce this average sentence length to about 12-15 words.
You can do this by
- breaking up long sentences
- adding short sentences
- removing unnecessary words and phrases
Let’s take your third para as an example. It’s fine, and many IELTS candidates would be very happy to write nearly as well as this.
In addition to this, health education and propaganda can largely improve people's health conditions by educating people to avoid diseases. An apt illustration is that AIDS, an incurable disease that kills hundreds of thousands of people every year, transmits via sexual intercourse and contaminated injection. If every individual is well aware of the serious consequences of catching HIV virus, then they will become much more prudent and cautious when facing various attractions. As this shows, it makes more sense to prevent diseases than curing it as some of them cannot be defeated.
92 words, 4 sentences, 23 words per sentence
Here’s a possible rewrite:
In addition, health education can help people to avoid disease. AIDS, an incurable disease which kills hundreds of thousands of people every year, is transmitted via sexual intercourse and contaminated needles. If people were aware of the consequences of catching HIV virus, they might behave more prudently. This shows it makes more sense to prevent diseases which cannot be treated.
60 words, 4 sentences, 15 words per sentence
Readers might ask - why rewrite if there are (almost) no errors?
Yes, there is a personal decision regarding style. Some people write longer sentences than others. But it's important to know how to write more concisely, and given that you only have 40 minutes in the test, it's very difficult to get everything right if you have 350 or more words. It's a lot easier to get 250 or 300 words correctly.
I've posted this quote before, but I think it's really appropriate. There is a difference between writing and speaking. In speaking, we use a lot of redundant and unnecessary words and phrases. In writing, every word must have a function, just as a machine has "no unnecessary parts"…
Vigorous writing is concise. A sentence should contain no unnecessary words, a paragraph no unnecessary sentences, for the same reason that a drawing should have no unnecessary lines and a machine no unnecessary parts. This requires not that the writer make all his sentences short, or that he avoid all detail and treat his subjects only in outline, but that every word tell.
in Elements of Style