Durham, N.C. — North Carolina public health officials are continuing to address public concern over the mutated strain of the H1N1 virus.

Three of four patients at Duke University Hospital with a drug-resistant form of the H1N1 flu virus died. The adult patients, treated in an isolated unit of the hospital over the last six weeks, tested positive for a mutation of the virus that was resistant to the drug Tamiflu, one of two medicines that help fight H1N1.

"It is something that we were expecting to see. We’ve seen it in the past with flus being resistant to the same Tamiflu. So we've been watching for it,” said Megan Davies, the state's epidemiologist.

Health officials said the fatal cases were rare and the patients were very ill with underlying compromised immune systems and multiple medical conditions. It is not clear whether their deaths were related to the flu infections.

Tamiflu is still the most effective treatment for the virus, and getting vaccinated is the best prevention for contracting the virus.

"The vaccine is effective against the resistant strain, as well as the sensitive strain. So the vaccine is still the best protection,” Davies explained.

The fourth patient with the H1N1 mutated strain is being treated with Relenza, the other drug approved to treat H1N1. The patient continues to recover at Duke University Hospital.

No resistance has been found to Relenza, health officials said.

However, concern over the virus continues to rise as people are urged to get vaccinated.

"A little bit scary, scary is the wrong word, (it is) disconcerting, but that's what flus do. That's is why we have to keep getting new shots,” Triangle resident Faye Sinclair said.

The Centers for Disease Control has identified the following as groups recommended to receive the H1N1 vaccine:

• pregnant women
• those who live with or care for children younger than 6 months
• health care and emergency medical services personnel
• children ages 6 months to 24 years
• persons ages 25 to 64 with underlying health issues

Health officials also say one of the best ways to help lower risk to the flu is to practice basic prevention tips, including frequent hand washing, avoiding others exhibiting symptoms and staying at home, if sick.

About 52 resistant H1N1 cases have been reported in the world since April, including 15 in the U.S. Last summer, health officials said two people in western North Carolina also had a drug-resistant form of the virus.

CDC officials have said that almost all the U.S. cases have been isolated.

Since the H1N1 pandemic began, 58 people in North Carolina have died as a result of the virus, health officials said. That number is based on reports from local health departments to the state as of Nov. 16.