Tamiflu, one of the leading medicines used to treat the flu, is in short supply of its liquid form of the virus treatment, Reuters reported.

Roche, the makers of Tamiflu said the liquid form of the medicine is in short supply due to manufacturing issues.

"There has been strong and early demand for Tamiflu Oral Suspension (OS) and we are experiencing a temporary delay in the packaging of Tamiflu OS," Tara Iannuccillo, a spokeswoman for Roche Holding AG's Genentech unit which manufactures the drug and uses distributors to supply retail pharmacies with the product.

Iannuccillo added that a brief shortage of the liquid form is expected through mid-January.

"We may be unable to fill complete orders from distributors for a limited time," she said.

The shortage and delay in packaging of the liquid version has not impacted supplies of regular Tamiflu 75 milligram capsules, Reuters reported.

The looming shortage comes during a tough and widespread flu season in the United States, Reuters reported.

The liquid version of the drug is used to treat the sometimes deadly flu virus in children between infancy and 13 years old and people who have difficulty swallowing.

People can ask pharmacists to mix the Tamiflu capsules into an oral suspension for people who need it, if the drug is not available in their area. Meanwhile, it is recommended that people continue to get flu shots to prevent the virus, Reuters reported.

Roche said additional supply of Tamiflu OS may be available in mid-January.

"We expect that these new supplies should meet demand for OS overall and we will continue to receive and ship out new supplies of Tamiflu OS and capsules throughout the flu season," Iannuccillo said.