The flu season is still young in the United States and the rest of the Northern Hemisphere, but Australia wrapped up its flu season months ago, and public health officials there have some disturbing news to report: The version of so-called swine flu that is resistant to the drug Tamiflu is spreading more easily in the land Down Under.

Swine flu refers to the H1N1 flu virus that caused a pandemic in 2009. It emerged in April in Mexico and spread swiftly around the globe, traveling to 214 countries and territories and killing more than 18,000 people, according to the World Health Organization. Humans were unusually vulnerable to this particular strain — a combination of viruses from birds, pigs and people — because their immune systems had never encountered it before.

Tamiflu, also known by the generic name oseltamivir, was frequently prescribed to patients, and it didn't take long for a version of H1N1 to emerge that was resistant to the drug. Luckily, this strain was a minor player, infecting less than 1 percent of people who were tested. In those cases, it spread between people only when they were in closed settings or had close contact with one another.

Fast-forward to 2011. In and around the Australian city of Newcastle, the Tamiflu-resistant H1N1 virus was spreading more easily among humans, according to a report being published in today's edition of the New England Journal of Medicine.

Public health officials took virus samples from 182 patients treated in doctors' offices and hospitals between May and August. They found that 29 of those samples — or 16 percent — turned out to be resistant to Tamiflu.

The 29 patients ranged in age from 4 months to 62 years, with a median age of 31; 17 of the patients were female, including three who were pregnant. Among all 29 patients, the most common flu symptoms were cough (experienced by 86 percent of patients) and fever (affecting 76 percent of patients). Seven patients required admission to the hospital, but none was treated in the ICU and none died.

The authors of the report, including three scientists working for WHO, warned flu experts in the Northern Hemisphere to be on the lookout for this flu strain — or any other strain that is resistant to Tamiflu — this winter.