KARACHI, Pakistan -- Measles cases surged in Pakistan in 2012, and hundreds of children died from the disease, an international health body said Tuesday.

In recent days Pakistani officials said they launched an immunization campaign to reach children in the worst-hit areas. But the country still struggles with a beleaguered health care system, unsanitary conditions in many regions and a lack of education about how to prevent disease. All those factors make it difficult to combat infectious diseases such as measles and polio.

Also, many oppose vaccinations, suspecting they are meant to harm their people.

A spokeswoman for the World Health Organization, Maryam Yunus, said that 306 children died in Pakistan of measles in 2012, compared to 64 the year before.

She said the jump was most pronounced in southern Sindh province, where measles killed 210 children in 2012. She said 28 children died there in 2011.

The World Health Organization did not give a reason for the increase in deaths, but a provincial health official in Sindh said that the disease hit areas where poor families did not vaccinate their children.

Provincial health minister Saghir Ahmed said 100 children died in Sindh province in December alone, mostly in areas where many people were not vaccinated.

He said health officials recently launched a campaign to vaccinate 2.9 million children in the affected areas of the province and urged parents to get their children vaccinated.

Many Pakistanis, especially in rural areas, view vaccinations campaigns with suspicion as a Western plot to sterilize Muslims. In December, nine health officials working to immunize Pakistanis against polio were killed by militants opposed to the campaign. Pakistan is one of three countries in the world where polio is endemic.

Sindh province, the area hardest hit by the measles outbreak, has also been battered by repeated floods in recent years that have damaged hospitals and clinics.

Measles is an extremely infectious disease spread by coughing and sneezing or personal contact. It causes a fever, cough and a rash all over the body. Most people who contract the disease recover, but it can be fatal for malnourished children.

Complications from the disease can include blindness, an infection that causes brain swelling, dehydration and diarrhea, and pneumonia.

According to WHO, 139,300 people died of measles worldwide in 2010.