Ryan Blow, who was 19 months, died with his parents, Frank and Lisa, at his bedside after his condition rapidly worsened, despite attempts to save him.
The news follows the deaths of Sussex schoolgirls Emma Harris and Alexandra Yates, who were both five. They had contracted the type C strain of meningococcal meningitis, a deadly bacterial form.
Microbiologists at Southampton University are now awaiting the results of tests that will prove which strain of the bacteria killed Ryan, who died in Southampton General Hospital on New Year's Day.
Martin Wale, consultant in communicable disease control for Southampton and South West Hampshire, said: "He went very quickly.
"His condition worsened so rapidly that the treatment just couldn't save him.
"His illness was pretty non-specific at first, but later in the day he developed the distinctive rash which suggested meningitis.
"Then he had a fit and he was taken to hospital. "We know he had the meningococcal bacteria but we just don't know yet which sub-type it was."
The boy's family have now been treated with antibiotics to protect them against the disease.Reuse content