* Confirmed Zika infections rise to 115
* Ministry expects more cases; virus to spread to other areas
* Singapore F1 race preparations on track - promoter (Adds details on pregnant woman, potential new cluster)
By Aradhana Aravindan
SINGAPORE, Aug 31 (Reuters) - A pregnant woman was among those diagnosed with Zika infections in Singapore, as the number of confirmed cases of the mosquito-borne virus in the city-state rose to 115.
The Zika virus, which has spread through the Americas and the Caribbean since late last year, is generally a mild disease but is a particular risk to pregnant women as it can cause microcephaly - a severe birth defect in which babies are born with abnormally small heads and underdeveloped brains.
The pregnant woman who tested positive lives in the Aljunied area in Singapore's southeast, where most previous cases have been detected. A member of her household was earlier diagnosed with Zika, the Straits Times newspaper reported.
Singapore announced the first locally contracted case of Zika late on Saturday, and the number of diagnosed infections has grown steadily this week.
In a joint statement with the National Environment Agency (NEA), the health ministry said it identified another potential cluster of Zika virus infection in east Singapore, involving three previously reported cases.
"Over time, we expect Zika cases to emerge from more areas. We must work and plan on the basis that there is Zika transmission in other parts of Singapore and extend our vector control efforts beyond the current affected areas," Minister for Health Gan Kim Yong said in the statement.
Several countries have warned pregnant women or those trying to conceive to avoid travelling to Singapore.
The outbreak and travel advisories come as the tourism industry in one of the world's busiest travel hubs already faces weak global economic growth. It is also just weeks ahead of the Singapore Formula One motor-racing Grand Prix - a major sporting and entertainment attraction.
Preparations for the race weekend are "on track and proceeding as per normal," the promoter, Singapore GP, said in an emailed statement.
In addition to 24 new Zika cases confirmed on Wednesday, nine were detected in the health ministry's 'look-back' testing of previous cases.
The NEA said it is to widen the scope of its mosquito control operations - clearing drains and spraying potential breeding habitats with insecticide - to include the new potential cluster area.
Most of the initial cases were among the hundreds of thousands of foreign workers, drawn mainly from the Asian sub-continent, who work on Singapore's construction sites and in the marine sector. These included 13 Indian citizens, said a person at the Indian High Commission in Singapore.
(Reporting by Aradhana Aravindan; Editing by Ian Geoghegan)