The new disclosures came the same day that the union representing American diplomats said mild traumatic brain injury was among the diagnoses given to diplomats hit by the attacks.
The U.S. State Department said more diplomats in Cuba have suffered symptoms following a new "acoustic attack" in August. Victims have reported other symptoms including brain swelling, severe headaches, balance problems and "cognitive disruption".
United States officials had previously said the attacks, initially believed to be caused by a potential covert sonic device, had started in autumn past year and continued until this spring 2017. Last week, Nauert had said at least 16 Americans associated with the US Embassy in Havana had been affected, but that the "incidents'" were no longer occurring.
In a statement, the AFSA said: "AFSA strongly encourages the Department of State and the US Government to do everything possible to provide appropriate care for those affected, and to work to ensure that these incidents cease and are not repeated".
"We can confirm another incident which occurred last month and is now part of the investigation", she said. Sound waves above and below the range of human hearing can cause permanent damage.
According to the Mayo Clinic, mild traumatic brain injury can cause temporary dysfunction of brain cells.
It is now known that Washington had alerted the Cuban government to what Havana dubs the "alleged incidents" as far back as February 17. The State Department said that the move was not a form of retaliation or a sign that the USA believes Cuba is behind the attack but rather to punish Cuba for its failure to keep American diplomats safe - something it is obligated to do under an global treaty known as the Vienna Convention.
"What has happened there is of great concern to the USA government", Nauert has said, defending the U.S.'s response. AFSA said they only met with 10 affected because the others were not available; the State Department has said that some of those affected have remained at their posts in Havana.
The Trump administration says the expulsions were a protest of Cuba's failure to protect diplomats as required under the Vienna Convention.
Cuba has denied any involvement in the attacks and says it is investigating the reports.
Diplomatic ties between the USA and Cuba were only restored in 2015 under the Obama administration.
US officials who worked in Havana said the petty harassment had slacked off in recent years, even before President Barack Obama announced in 2014 that he would reestablish full diplomatic ties with Cuba after decades of estrangement between the two countries.