The reproduction rate of coronavirus is "highly likely to be over 1", according to the Department of Health.
The current estimate of the reproduction, or R number, is 0.8 – 1.8.
R represents the number of individuals who, on average, will be infected by a single person with the infection.
Chief Scientific Adviser Professor Ian Young said the data "underlines the need for continued vigilance".
The department said community transmission remains low in Northern Ireland but added that the number of positive tests per day has increased three fold from early July.
A further 43 people have tested positive for coronavirus in the past 24 hours. The total number of people who have tested positive since the pandemic began is 6,049. Health Minister Robin Swann said the figure of 43 should serve as "a wake-up call.for the complacent".
The Public Health Agency today said 23 clusters have been identified since May 25 and 11 are ongoing. A cluster is two or more cases in a key setting such as a home or workplace.
The Public Health Agency (PHA) said some 168 cases have been associated with the 23 clusters and nine of the clusters have had five or more cases associated with them.
The Department of Health releases the R number weekly. It says it does not have a fixed value "but varies with time, and is likely to be different every day".
"When community transmission of the virus is very low, R will show a high degree of volatility and be heavily influenced by small local clusters. It will therefore no longer be the most informative or important number for the purpose of policy decisions. In these circumstances, the number of positive tests per day is likely to be a more important parameter."
Professor Ian Young said there are five ways in which people can keep themselves and others safe - rigorously maintain social distancing; wash hands well and often; wear face coverings in enclosed spaces where social distancing is difficult; co-operate fully with the test, trace and protect programme in terms of getting tested and self-isolating when required; and download the StopCOVID NI app.
Read more: 43 new cases and 11 active clusters in Northern Ireland
