The death of a young mother and a vaccine that was ineffective in Australia has experts worried about how hard the United States will be hit by this year’s flu.

Alani Murrieta was diagnosed with the flu only one day before she died of the illness in late November.

The 20-year-old Arizona mother’s death could be a problematic sign of things to come.

Experts say the United States is bracing for what could be a rough flu season.

Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical Center in Tennessee, said the young woman’s death is also a sad reminder that influenza can be deadly.

“When you have a young adult who has an overwhelming influenza infection, it can obviously be very, very serious,” Schaffner told Healthline. “It can cause pneumonia all by itself and the systemic inflammatory response can wreak havoc with many organs in the body.”

“Flu can be a nasty infection,” he added. “Every once in a while, it chooses you and it makes you terribly, terribly ill. I use the term gravely ill in its root sense. It can send you to the grave as it did with this young woman.”

The annual flu season is just beginning in the United States.

Health experts across the country have looked to the Southern Hemisphere for an indication of what might be in store for the Northern Hemisphere.

Australia has just emerged from a rough flu season, with record high numbers of laboratory-confirmed influenza notifications, and a higher than normal number of deaths and hospitalizations due to influenza.

The number of reported cases of flu had surpassed 215,000 by mid-October.

That far exceeds the 59,000 cases during the 2009 H1N1 influenza pandemic.

In Australia this year, influenza A (or H3N2) viruses dominated, the same strain thought to have infected Murrieta.

A flu season dominated by this type of strain is often characterized by more severe illnesses, particularly among the young and old.

Preliminary estimates from Australia suggest that this year’s vaccine against influenza A was only 10 percent effective.

This could be indicative of a difficult flu season ahead in the United States.

“The Australian experience has made a large impression on everyone here who knows anything about influenza,” Schaffner said. “The early viral strains that we are now isolating from around the country in the United States are very close. Basically, they’re the same as the H3N2 strains that were active in Australia, so we are braced for a serious influenza season.”

Vaccine experts have long known that the current method of developing flu vaccine is far from perfect.

It has been suggested that the low efficacy of the flu vaccine against influenza A in Australia may be due to the method in which the vaccines are created in chicken eggs.

“We’re hung up on a production method we have used for over 50 years,” Schaffner said. “When we take the wild virus, and wish to grow it up in eggs… the virus adapts to the eggs so that it multiplies most readily. In doing so, the virus changes sufficiently from the wild virus… such that the vaccine we create from the egg virus is not exactly on target.”

The result is a vaccine that may not be effective at protecting against H3N2.

Despite this, experts emphasize that getting vaccinated against the flu is still important.

Even if it doesn’t prevent illness entirely, if you get the flu despite getting vaccinated, it is likely to be a milder case that is less likely to result in complications like pneumonia.

“Vaccine is the best preventive we currently have for flu. Take it,” Stephen Morse, PhD, a professor of epidemiology and an influenza expert at Columbia University in New York, told Healthline. “The alternative could well be worse. Even a relatively ineffective vaccine may reduce disease severity. You may get some protection, and preventing 60 percent of flu cases is theoretically enough to stop its spread. I’d gladly take those odds.”

Just under half of the U.S. population gets vaccinated against influenza each season and experts are encouraging people not to believe myths like the influenza vaccine will make you sick with the flu.

“Influenza vaccine doesn’t cause influenza,” Dr. Lee Norman, chief medical officer of the University of Kansas Hospital, told Healthline. “It might cause an immune response and some mild symptomatology, but it doesn’t cause influenza. Be thankful your arm is achy for a day. It is your immune response thanking you for stimulating it.”

Schaffner says there is still time to be vaccinated, even though the flu season is getting under way.

“It’s not too late, although it takes 10 days to 2 weeks for your protection to become maximum. Influenza has not struck every community in our large country simultaneously,” he said.

Given the experience of the Southern Hemisphere’s flu season, he says getting vaccinated sooner rather than later is a wise choice.

“We are talking about the Australian experience and urging people to run, not walk, to their healthcare provider,” Schaffner said. “We can get our flu vaccines here in our pharmacies. It’s widely available. It’s not too late but don’t linger.”