Although the investigation is continuing, preliminary findings indicate that three of the confirmed cases spent the night of 29 April in a small room together with the initial case at a time when she was symptomatic and coughing frequently. These cases include the woman’s two sons and a second brother, aged 25 years, who is the sole surviving case among infected members of this family. Other infected family members lived in adjacent homes.

All confirmed cases in the cluster can be directly linked to close and prolonged exposure to a patient during a phase of severe illness. Although human-to-human transmission cannot be ruled out, the search for a possible alternative source of exposure is continuing.

Both the Ministry of Health and WHO are concerned about the situation in Kubu Sembelang and have intensified investigation and response activities. Priority is now being given to the search for additional cases of influenza-like illness in other family members, close contacts, and the general community. To date, the investigation has found no evidence of spread within the general community and no evidence that efficient human-to-human transmission has occurred.