The health ministry in Cuba has confirmed the first outbreak of cholera in the capital, Havana, in over half a century.
The outbreak was first detected on 6 January and 51 people have been infected so far.
Doctors have been going house-to-house in many areas of the city to check for signs of sickness. The outbreak comes at the height of the tourism season.
The first cases were traced to a baseball game at the Latin American Stadium in Cerro, Havana.
Fans from all parts of the city had gathered to watch their team, the Industriales, play.
An official said either the pork sandwiches or soda "was contaminated at a game earlier this month".
"Even some of the baseball players became sick," she added.
The health ministry statement said the outbreak had begun in Cerro and later spread to other municipalities in the capital.
Tens of thousands of tourists are visiting Havana, but there have been no reports of foreigners catching the illness.
Community clinics and family doctors are on high alert and giving out instructions to prevent the disease.
Transportation hubs have passengers sterilising their shoes before leaving town, and eateries are being systematically inspected and sometimes closed.
Three Havana hospitals have been designated to handle cholera cases - one for adults, another for children and a third for pregnant women.
Cholera is generally not fatal, but can kill in just a few hours when diarrhoea and vomiting cause dehydration, especially among the elderly.
The illness runs its course within a week, making it relatively easy to track, but at the same time is highly contagious, spreading from hand to mouth, through contaminated food and the water supply.