Flu in the US has become resistant to Tamiflu

This winter, a strain of flu resistant to Tamiflu (oseltamivir), the most commonly used flu drug, is spreading in the United States.

The Centers for Disease Control and Prevention (CDC) describes the situation as serious, and has asked doctors to rely on older drugs and avoid prescribing Tamiflu when it isn't necessary.

Flu samples were tested for resistance, and 49 out of 50 were resistant to Tamiflu, although they could be treated with other drugs. Most people with flu recover without any medicine.

Three types of flu are of concern: H1N1, H3N2 and B. The one showing resistance is H1N1.

Resistance of viruses and bacteria to drugs has become a common problem, mainly because of the unregulated use of flu drugs and antibiotics, so a way is needed to control their use.