The grandmother of the 5-year old boy who was the first confirmed case of Ebola in Uganda has also succumbed to the deadly disease while undergoing treatment in Uganda, the World Health Organization said on Thursday.

The news has sent shock waves through the region because the virus has jumped from the eastern part of Democratic Republic of Congo, where health organizations have been battling to contain an epidemic for the past 10 months.

A three-year old boy, a relative to the two deceased, is still alive and undergoing treatment at Bwera Hospital Ebola treatment unit in western Uganda. The Health Ministry said in a statement that the three were in a group that crossed over to Uganda through the western border post at Bwera.

The family of six, including four children, then sought medical assistance. A blood sample was drawn and sent for testing at the Uganda Virus Research Institute. It tested positive for Ebola. So far, 27 people, who had been in contact with the first victim, have been listed as infected. The DR Congo team has delivered 400 doses of the Ebola vaccine to Uganda, said the WHO.

Ebola is a hemorrhagic viral disease with an incubation period of 2-21 days, beginning from contact with body fluids of an infected person. Once in the blood, the virus attacks immune cells, then infects vital organs.

In Kenya, all airport arrivals are screened while truck drivers and others crossing the Kenya-Uganda border in Malaba must undergo Ebola screening. The Kenya Health Ministry has issued an alert and said an Ebola contingency plan is in place to guide the implementation of prevention and response activities.

Earlier, the Kenyan government had revealed that the 170 medical personnel who were sent to Sierra Leone and Liberia in 2015 will man points of entry to detect Ebola cases. The team that returned in June last year was part of the African Union mission in Ebola in West Africa.

Contingency plans

Contingency plans had long been put in place in Uganda for possible imported Ebola cases, according to WHO. The government has vaccinated about 4,700 health workers in 165 health facilities, including the one where the dead boy was treated.

"This is a sobering development that everyone has been working to avoid and highlights the complexity of the Ebola outbreak in the Democratic Republic of the Congo," Robert Redfield, director of the country's Center for Disease Control and Prevention, said in a statement.

Redfield had issued a warning, a week ago, that the outbreak in the DR Congo could spread outside the country. He added that there was a risk of the current supply of vaccines running out before more is produced.

The new developments have put increased focus on the region's preparations against cross-border diseases. This week, the East African Community, encompassing Kenya, Uganda, Tanzania, Rwanda, Burundi and South Sudan, launched a cross-border disease preparedness exercise in the Kenya-Tanzania border.

Earlier this week, the WHO had announced that there could be signs of the pandemic transmission slowing down in the DR Congo, following improved security and access to medical personnel in high-risk areas.