For the past two weeks, Beijing resident Duan Jiayi has been relaxing in southern Hainan, far away from the hazardous smog that wrecked her health back home.

"During the worst spell last month, I had a fever, I lost my voice and I couldn't speak for days," she told The Straits Times.

So, a fortnight ago, she packed up and left for Hainan's resort city of Sanya, where her family bought a holiday home a few years ago.

Ms Duan, 26, said the fresh air helped her "recuperate significantly". And it seems many other residents in northern China had the same thought.

Indeed, bad news for northern China - which suffered a severe deterioration in air quality last month - has been good news for southern and western China, going by the tourist numbers.

According to the latest figures from the country's Ministry of Environmental Protection, concentrations of harmful PM2.5 particles in Beijing were up by 75.9 per cent from Nov 15 to Dec 31 last year, compared with levels the year before.

Over the same period, bi mai - or avoiding smog - became a top search term on travel websites in China. Tour agencies launched bi mai packages, mainly to places touting nature and fresh air.

Furthermore, the smoggiest days in northern China tend to be during its cold winters, which contrast with milder climates elsewhere in the country.

According to Beijing Youth Daily, tour agents say domestic travellers have been making a beeline for southern or western provinces such as Hainan, Yunnan and Guizhou.

Meanwhile, the top foreign destinations are Jeju island in South Korea and the Seychelles, as well as South-east Asian getaways such as Phuket and Bali.

"The more severe the smog in a place at a certain time, the more inquiries and bookings of bi mai packages there will clearly be," a representative from travel website Ctrip was quoted as saying.

Sanya - located at the southern tip of Hainan island and known for its beach resorts - was the top destination for domestic tourists last month, according to travel website Qunar.

The number of Beijing and Tianjin residents who visited Sanya rose by 30 per cent over levels in the same period the year before, as 70,000 tourists thronged its main tourist sites over the long New Year weekend.

It is a trend Ms Duan believes will continue, given the poor air that has continued to blight the country despite efforts to cut back on emissions.

"Everyone wants to avoid the smog, as long as they have the money and time to do so," she said. "I'll do this every year if I have to."