Why do they occur so much in northern European countries?

This became almost a nation-wide problem and occurred in other countries as well.

More than 90 percent of cases occur in developing countries.

"More than 90 percent of new infections occur in developing countries," he said.

It has also occurred in other countries, such as Korea.

"The Government was very professional throughout, a situation that sometimes does not occur in other countries," she said.

They are found throughout the world, with most species occurring in hot countries.

But is this really the way it has occurred in other countries?

Ninety percent of the world's population growth is occurring in developing countries.

The rapid growth of world population since 1950 has occurred mostly in developing countries.