LONDON, ONT. -- The Middlesex-London Health Unit (MLHU) is trying to determine how COVID-19 is spreading through a in a residence at Western University.

An outbreak has been declared after four individuals from London Hall residence have tested positive for COVID-19.

"The way in which we link them all is not entirely clear," according to Dr. Alex Summers, associate medical officer of health at MLHU.

"We declare an outbreak when we see evidence of transmission where it has likely spread beyond case to case. We are doing person-to-person contact tracing, plus additional steps like shifting energy to a zone defence to disrupt transmission."

The individuals in the 417 student residence have been contacted and are currently being advised to self-isolate. The health unit is following up with close contacts of these cases to ensure that they are tested and quarantined.

"Those students who have tested positive are isolating outside of residence. We are delivering them meals, and our staff are in regular contact to ensure students are well supported," says Chris Alleyne, associate vice-president of housing and ancillary services.

A resident of London Hall told CTV News Monday morning that she is "a little worried" but not surprised there has been transmission.

"I totally understand why it has happened," says Lauren Berridge, a London Hall resident.

"My floor is pretty good, but on the floors below me there is parties every night."

The MLHU has been preaching for students not to mingle during the pandemic.

"This outbreak highlights the need to limit close contact to only those within your dorm room, maintain two metres physical distance, wear a mask and stay home or in your suite if you feel unwell," says Summers.

MLHU and Western University are stopping visitors from going in and out of London Hall, and trying to ensure minimal visits between floors and between rooms on every floor.

"For a couple floors that may be more exposed than others there will be expanded testing to understand if there is additional spread," says Summers.

However Summers is encouraged by what health officials have learned through the pandemic.

"We have learned what we need to do to disrupt transmission in which people live closely together. Through long-term care and group homes, and we will learn more through this residence."

Students, staff and faculty who have COVID-19 related symptoms, have been notified by public health, or notified by the COVID-19 alert app telling them they have been exposed to a confirmed case should self-isolate until they can be tested.

Members of the Western community can receive a COVID-19 test their COVID-19 testing centre in the Western Student Recreation Centre.

The testing centre reopens Tuesday 9:30 a.m.