Ants are "social" insects - they live together. As such, one can be found close to another.
A colony of ants appeared around a large hive in the Antarctic Base. They may have been in some way mutated by the T-Veronica virus. Alexia Ashford as their 'queen', demonstrated an ability to control these ants. She planned to use them to infect the whole world with T-Veronica.
A tropical species of ant was infected with the T-Veronica virus in 2002, in South America.