London, Jul 6 (IANS): A measles outbreak has hit the Yanomami isolated Amazon tribe on the border of Venezuela and Brazil, according to a London-based NGO that works to protect tribal peoples.

According to Survival International, the outbreak has put 23 tribe members in the hospital and is threatening hundreds more, reports CNN.

"Any remote indigenous people with little contact with mainstream society have low resistance to diseases that are introduced from outsiders," Sarah Shenker, a senior researcher at Survival International, said on Thursday.

"That's why this epidemic of measles that has broken out on the Venezuela-Brazil border in recent months is particularly worrying for the Yanomami and could be catastrophic. It could wipe out whole communities."

Another NGO Watinaba, which defends the rights of various Amazon indigenous groups in Venezuela, tweeted about the measles outbreak on Thursday, showing various Yanomami who have contracted measles and asking for vaccinations for the tribes people.

The Yanomami remain at particular risk given their low immunity to diseases and the difficulty in reaching those who may need the vaccine, Shenker said.

The Yanomami make up the largest semi-isolated tribe in South America, whose territory spans the jungles and mountains of northern Brazil and southern Venezuela, CNN reported.

During the 1980s, over 40,000 gold miners entered their territory, shooting tribes people, destroying their villages and exposing them to disease, according to Survival International.

The Yanomami lost 20 per cent of their population during these incursions.

Today, it is estimated that 35,000 Yanomami remain.