Measles, which is highly contagious, can be entirely prevented through a two-dose vaccine, but the World Health Organization (WHO) has in recent months sounded the alarm over slipping global vaccination rates.

"Preliminary global data shows that reported cases rose by 300 percent in the first three months of 2019, compared to the same period in 2018. This follows consecutive increases over the past two years," it said in a statement.

"While this data is provisional and not yet complete, it indicates a clear trend. Many countries are in the midst of sizeable measles outbreaks, with all regions of the world experiencing sustained rises in cases," WHO further said.

The agency noted that only about one in 10 actual measles cases are reported, meaning the early trends for 2019 likely underestimate the severity of the outbreaks.

So far this year, 170 countries have reported 112,163 measles cases to WHO. At this time last year, 163 countries had reported 28,124 cases.

"Spikes in case numbers have also occurred in countries with high overall vaccination coverage, including the United States," WHO said.

"The disease has spread fast among clusters of unvaccinated people," it added.

New York's mayor declared a public health emergency in parts of Brooklyn last week, after a measles outbreak emerged in an ultra-Orthodox Jewish community, where some had resisted vaccination on religious grounds.

WHO said that the most dramatic rise in cases -- a 700-percent increase compared to last year -- has been reported in Africa, which has weaker vaccination coverage than other regions.