The World Health Organization has confirmed that an outbreak of the ebola virus that has killed 70 people in Guinea has spread to Liberia. Two cases of the disease have been reported in the country, and Reuters says that another 11 deaths in Liberia and Sierra Leone — both of which share borders with Guinea — are suspected to be linked to ebola.

The WHO took seven samples from the Foya district of Liberia, a region less than 12 miles (20 kilometers) from the border with Guinea. The organization said two of those samples tested positive for the ebola virus. The outbreak in Guinea was first reported on March 23rd, when the WHO and Guinea's Ministry of Health acknowledged fatal cases of the ebola virus in south-eastern areas of the country. The disease then spread to Guinea's capital, Conakry, with four suspected cases of the virus confirmed by laboratory analysis. Guinea's Ministry of Health claimed a fatality rate of 63 percent, with 70 deaths from 111 cases of haemorrhagic fever. Ebola appears to have made its way into Liberia more than a week ago: the WHO said that a 35-year-old woman who died on March 21st tested positive for the virus.

11 deaths in Sierra Leone and Liberia are suspected to be linked to Ebola

Guinea's neighbors have reacted to quell the spread of the disease. Reuters reports Senegal closed its land border with Guinea on Saturday, and halted the operation of weekly markets in the area. Senegal has also implemented sanitary checks on flights between its capital Dakar and Conakry, while West African airline Gambia Bird has delayed the launch of a new route to Guinea's capital.

Ebola is spread primarily through contact with infected bodily fluids. It's a highly contagious and regularly lethal disease — 68 percent of all recorded cases in the past have been fatal — that has killed more than 1,500 people since its first recorded transferal to humans in 1976. The confirmed cases in Guinea and Liberia are particularly notable because they are the first to be recorded in the west of the continent — prior to this outbreak, every known case of fatal Ebola infection (excluding laboratory accidents) took place in in south and central Africa. Should the outbreak continue to gather pace, it could stretch West African health providers to the limit.