Wikipedia has a background on 'Havana Syndrome' [0]. The July 2019 study discussed in the article is paywalled but can be found in [1]. 'Havana Syndrome' has been previously discussed on HN [2] [3].<p>[0] <a href="https://en.wikipedia.org/wiki/Havana_syndrome" rel="nofollow">https://en.wikipedia.org/wiki/Havana_syndrome</a><p>[1] <a href="https://jamanetwork.com/journals/jama/article-abstract/2738552" rel="nofollow">https://jamanetwork.com/journals/jama/article-abstract/27385...</a><p>[2] <a href="https://news.ycombinator.com/item?id=18426129" rel="nofollow">https://news.ycombinator.com/item?id=18426129</a><p>[3] <a href="https://news.ycombinator.com/item?id=15460539" rel="nofollow">https://news.ycombinator.com/item?id=15460539</a>