Background: On 3 March 2013, an announcement was made concerning the possible functional HIV cure of the "Mississippi baby" at the Conference on Retroviruses and Opportunistic Infections (CROI) in Atlanta, Georgia, USA. Immediately following this announcement, word spread across traditional media outlets, and social media platforms such as Twitter, rousing tremendous public excitement.Objective: The purpose of this study was to examine the frequency, content, and sentiment of HIV cure-related messages (tweets/retweets) on Twitter around the HIV "cure" Mississippi baby announcement on the 3 of March 2013.Methods: We obtained a dataset containing all HIV cure messages between 13 January and 16 May 2013 and conducted qualitative analyses on a 1,111-message sample.Results: A sharp increase (2,786%) in HIV cure-related messages occurred immediately following the announcement. However, this sharp increase only lasted approximately 19 days. Out of our sample of 1,111 messages most were from individuals (68.1%) or news organizations (18.3%), including the single most retweeted post from the BBC (20,047 retweets). 36.6% of these messages were coded as opinion/commentary and 26.7% were coded as news. The proportion of messages with neutral sentiment increased (42.5% to 53.9%; P = 0.003 while the proportion of those with negative sentiment decreased (15.6% to 9.2%; P = 0.01.Conclusions: The Mississippi baby announcement substantially increased HIV curerelated social media messages. Tweets from individuals dominated this platform; messages from public health agencies were relatively under-represented. The increased public attention garnered after the announcement was short-lived. Similar surges in public attention following future HIV cure breakthrough announcements may offer opportunities to reduce negative perceptions of HIV and improve community engagement.