I am a movie director and I just received the following movie plot. Could you help me answer this question? If not, let me know by writing "Not answerable". Plot title: La Habanera Movie plot: Astree and her aunt from Sweden are vacationing in Puerto Rico. Astree is enchanted by the local habanera music as well as by Don Pedro de Avila, a rich and powerful landowner and former bullfighter. Upon embarkation, she spontaneously decides to stay; she runs down the gangway, finds him waiting for her, and soon is married. Ten years later - it is now 1937 - Astree finds herself trapped in an unhappy marriage. Her paradise has turned to hell; her son, Juan, is her only reason to stay. Meanwhile, in Stockholm, Dr. Sven Nagel, a former lover of Astree, and his associate, Dr. Gomez, bid farewell. They are departing for Puerto Rico to investigate the mysterious and deadly Puerto Rico fever. On the island, their arrival is met with dismay by Don Pedro and his business associates as they fear the focus on the Puerto Rico fever will depress their business, so they plan to deny its existence. An earlier attempt by researchers from the Rockefeller Institute to find a cure had been a failure, and the resulting publicity had depressed the local economy and resulted in widespread famine. Once in Puerto Rico the two investigators, receiving no local support, proceed to conduct their studies on their own in the hotel room. Meanwhile, Astree has a fall-out with her husband about their son. He wants him to learn about bullfighting, while she has been teaching him about snow and Sweden. Thus Don Pedro decides to take the education of Juan out of her hands. Astree in response books a passage to leave Puerto Rico with her son to return to Sweden. Meanwhile, the Puerto Rico fever is starting to claim its first victims, and Drs. Nagel and Gomez search for a cure secretly. Don Pedro learns about Astree's plans and suspects that Dr. Nagel is involved. He invites him for a soiree to have an opportunity to have his hotel room searched and gain evidence against him for his arrest and deportation. Thus at the soiree Dr. Nagel and Astree meet and fall in love again. Astree sings La Habanera presumably for her husband, but... My question: What mysterious and deadly fever they are investigating?
A:
Puerto Rico