The rapid spread of seasonal influenza in China in recent weeks has increased the demand for a certain antiviral medication, prompting health experts to warn against hoarding of the pills or administering them to children without a doctor's advice.

The drug baloxavir marboxil, sold under the brand name Xofluza, is approved for use among adults, as well as children age 5 and above. While the original market price per strip of Xofluza, comprising two 20 milligram tablets, is 222 yuan ($30) in China, the prescription drug is currently being sold at over 300 yuan on some e-commerce platforms.

Cases of influenza, a viral infection affecting the human respiratory system, have been on the rise since December.

The positivity rate among people visiting hospitals with flu-like symptoms rose 6.2 percent during the week ending Dec 29 compared with the week before, according to data released earlier this month by the Chinese Center for Disease Control and Prevention.

"The prevalence of flu in northern provinces is more severe, but the overall level is lower than what was seen during the same period of the last flu season," said the China CDC.

In Northeast China's Liaoning province, the number of flu cases surged in December, with an average weekly growth rate of over 123 percent, local authorities said last week.

Official data showed that the influenza A virus is responsible for more than 99 percent of positive flu cases nationwide. For the week ending Dec 29, about 99.7 percent of flu patients were infected by the strain.

Speaking about the surging demand for Xofluza, Sun Boyang, a pharmacist at Peking University People's Hospital, told China Central Television that compared with another common flu medication called oseltamivir, the drug baloxavir marboxil is easier to administer.

While oseltamivir — sold under the common brand name Tamiflu — is usually prescribed for five consecutive days, with a daily dosage of two tablets, Xofluza only needs to be administered once throughout the entire course of illness.

As some concerned parents are stocking up on the relatively newer antiviral medication in anticipation of a drug shortage, Sun said that children infected with the flu virus should first be taken to a hospital for evaluation, and Xofluza should be administered only under professional guidance.

Pregnant or lactating women should also take special precautions while using this antiviral medication, the pharmacist added.

Wang Quan, a physician at Capital Medical University's Beijing Children's Hospital, said that any antiviral medication is most effective when administered within 48 hours of a confirmed infection.

Parents are also advised to administer antipyretic medication carefully based on a child's age and weight, as well as the drug's composition, Wang said.

Pharmaceutical company Roche, the only supplier of Xofluza in China, allayed fears of a drug shortage and said on Monday that it has sufficient flu medication in stock. The company attaches great importance to securing inventories of Xofluza during this flu season, it added.