It's the worst case scenario for the coming flu season: A person at high risk for flu complications who is unable to get a flu shot.
But it's not a hopeless situation. Many have survived past flu seasons without the vaccine, and many will make it through this one.
People can take precautions, such as regularly washing hands and avoiding ill people, that can reduce their risk of getting influenza. And, if they are infected, they can do things, such as seeking prompt care with antiviral drugs, that can reduce the severity of their illness.
"I cannot over-emphasize the importance of hand washing to protect against infectious diseases," said Guillermo Cole, spokesman for the Allegheny County Health Department. "Wash your hands after you use the bathroom, before and after preparing food, before eating and after sneezing or coughing in your hands."
The flu virus is commonly spread through airborne droplets from coughs or sneezes. But it also can be picked up from surfaces, such as if you touch a dirty doorknob or shake hands with a person who has the flu and has sneezed in his unwashed hand, Cole said.
Other precautions include covering your nose and mouth with a tissue or your sleeve when coughing or sneezing so viruses are not spread.
Also, people over the age of 65 should be immunized with the pneumococcal vaccine, which protects against diseases that include pneumonia, a potentially fatal complication of the flu.
To prevent spread of the disease, Pennsylvania health officials recommend people stay home from work, school and errands when they are sick.
If a spouse is sick, it's not a bad idea for the other to sleep in a separate room, said Dr. Lawrence Ellis, professor of medicine at the University of Pittsburgh School of Medicine.
One high-risk population might be hard to avoid -- young children.
According to Dr. Richard Zimmerman, an associate professor of family medicine at Pitt, children are the primary transmitters of influenza in a community.
Children can transmit the flu virus up to six days before they show flu symptoms, he noted. Adults, by contrast, shed the virus for up to one day before symptoms appear.
In addition to good health habits, antiviral medications may be used to prevent and treat the flu.
Three antiviral drugs -- amantadine, rimantadine and oseltamivir -- are approved and commercially available by prescription for preventing flu. They are about 70 to 80 percent effective in preventing the flu in healthy adults.
In addition to prevention, those three drugs can be used to treat the flu. Another antiviral prescription drug, zanamavir, also is available for treatment. All can reduce the severity of symptoms and shorten the course of the disease, but only if they are taken within 48 hours of the outbreak of symptoms. The drugs, which must be taken for five days, also can make a patient less contagious to others.
The antivirals differ in terms of who can take them and how they are administered. Patients should contact their doctors to help them decide if they should get an antiviral drug and if so, which one to get. None of the antivirals is approved for use in children under age 1.
In most cases, antivirals are used for prevention in the event of a flu outbreak, Zimmerman said. Doctors may give patients antivirals if they are high risk for complications from the flu, or in close contact with a high-risk person, so not to spread the illness to him or her.
Other standard treatments include resting at home, drinking plenty of fluids and taking acetaminophen (such as Tylenol) or ibuprofen (such as Advil) for fever and pain. Zimmerman warned that aspirin should not be taken by people with the flu because the combination has been associated with Reye syndrome, an illness that can cause liver and brain damage.
"If you have the flu or think you have the flu, the best thing to do is stay home," Ellis said. But sometimes a visit to the doctor is necessary, he added.
One example is the "double dip." That's when a flu patient feels bad, gets better but then feels worse again.
"If a double dip effect occurs, see your doctor immediately," Zimmerman said. "A double dip could be the sign of a secondary bacterial infection, such as pneumonia." And it is usually the complications of the flu, such as pneumonia, that prove fatal.
According to the Centers for Disease Control and Prevention, an average of 36,000 Americans die from flu each year.
It is important to call your doctor or visit the emergency room if you have an intestinal flu and can't keep fluids down, have a hard time breathing, suffer chest pains, cough up blood or have pain when swallowing. Also, seek care immediately if you have a fever above 102.5 degrees or have sweats or chills that last for days.