Two university students were taken to hospital with meningitis.
The UK Health Security Agency (UKHSA) reported that the students from the University of Brighton have received hospital treatment for the infection.
Specialists are working with the university and health partners, a UKHSA spokesman said.
Charlotte Flynn, consultant in health protection at UKHSA South East, said students and staff should be aware of symptoms of meningitis, which can be "easily confused with a hangover".
These can include fever, headache, rapid breathing, drowsiness, shivering, vomiting and cold hands and feet.
It can also cause a rash that does not fade when pressed against a glass.
A spokeswoman for the University of Brighton said the students are recovering.
Ms Flynn said: "We know that students and staff will be feeling worried about the likelihood of further cases, however we would like to reassure them that close contacts of the individuals have been given antibiotics as a precautionary measure.
"Advice and support is being offered to the wider student community and we're monitoring the situation closely.
"Students are particularly at risk of missing the early warning signs of meningitis because they can be easily confused with other illnesses such as a bad cold, flu or even a hangover.
"That's why it's vital that if a friend goes to bed unwell that you check on them regularly and don't hesitate to seek medical help by contacting their GP or calling NHS 111 if they have these symptoms or you're concerned about them.
"This could save their life."
A spokeswoman for the University of Brighton said: "We are aware of two recent cases of meningococcal meningitis among our students. Both individuals are recovering, and we've worked closely with the UK Health Security Agency to identify and treat all close contacts as a precaution.
"We've re-issued guidance to students and staff to raise awareness of symptoms and are following expert advice to manage the situation.
"Meningococcal bacteria don't spread easily, and only those with prolonged, close contact are at slightly increased risk. Students and staff who haven't had that level of contact are at no greater risk than the general population."