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After spending a few days in bed with a fever, sore throat, aches and other symptoms most likely caused by the H1N1 virus, you feel ready to jump back into your routine.

But new evidence suggests that you could still be spreading the virus for a few days after your fever breaks.

Researchers with the U.S. Centers for Disease Control and Prevention found that elementary school children who contracted the H1N1 virus during an outbreak earlier this year tested positive for the virus up to 13 days after the onset of fever.

The findings, led by researchers at the CDC and the Pennsylvania Department of Health, are being presented at the Infectious Disease Society of America's annual meeting in Philadelphia.

They raise questions about H1N1's contagiousness and whether those infected should take steps to avoid infecting others even after they've recovered.

In the study, researchers focused on a group of 26 children infected by an H1N1 outbreak at a Pennsylvania elementary school in May and June. Researchers used two tests to confirm illness in each child and detect how long the virus remained present in their bodies.

One test is known as real-time reverse-transcriptase polymerase chain reaction – or rRT-PCR for short. The second test involved confirming presence of H1N1 through testing specimens taken from the children.

Using the first test, researchers found that the children tested positive for the H1N1 virus from one to 13 days after the onset of fever, with a median period of six days. Using the virus culture test, they found H1N1 present from one to seven days after the onset of fever, with a median period of five days.

It's a significant finding that may change conventional thinking about the contagious period associated with H1N1.

The Public Health Agency of Canada says that people with H1N1 may be contagious for up to seven days after the onset of symptoms. But as more research emerges suggesting that period could last even longer, it may require public health officials to modify their communication.

However, one of the researchers involved in the study said the findings should not be cause for alarm and that they must be examined further to assess potential implications.

The results “should be interpreted cautiously, because detection of the virus may not mean that patients are likely to transmit the virus to others,” said Achuyt Bhattarai, an investigator with the CDC.

The medical community still doesn't have a great understanding of the relationship between the presence of a virus in a given individual and their ability to pass it onto others, the authors said.

It's a link that must be studied further in order to determine the risk people who have recovered from viruses such as H1N1 pose to others in the days following their recovery.