In other US measles developments, Arizona's Maricopa County reported two more cases.
The infections are occurring amid a global rise in cases and gaps in MMR vaccination.
Several states have now reported cases amid a global spike in measles activity.
Increased activity continues into the new year, with gaps in vaccine coverage and the season's peak still ahead.
The vaccine campaign targets 610,000 people in South Sudan's Western Equatoria state.
The new cases come after the CDC urged health providers to watch for fever and rash in people who had traveled overseas.
The new center in Tokyo will support collaboration to better prevent, detect, and respond to public health threats in the region.
The new detection comes just a week after the CDC warned health providers about a rise in imported measles cases.
GSK has applied for expanded RSV vaccine use in adults ages 50 to 59 who have underlying health conditions.
Imported measles cases are rising, with two localized outbreaks reported.