From left: Kevin Harrod, Ph.D., Carlos Orihuela, Ph.D., and J. Victor Garcia-Martinez, Ph.D.As the flu lingers late into the season, many are asking how it spreads so easily and which precautionary steps actually help. To separate the science from the noise, three UAB experts, representing the departments of Microbiology and Anesthesiology and Perioperative Medicine, outline what happens in the body during infection and how to slow transmission.
“The signs and symptoms of influenza illness are complex and typically represent bodily responses that are both beneficial as well as detrimental,” said Kevin Harrod, Ph.D., professor in the Department of Anesthesiology and Perioperative Medicine.
What is happening inside your body
Flu symptoms often arrive together. Fever is believed to make the lungs less hospitable to viral multiplication. Coughing and sneezing help clear excess mucus from the airways. The heavy fatigue and body aches are common when the immune system is working to clear the infection.
“Largely speaking, the body aches, malaise, and fatigue that occur during infection are driven by the immune system activating critical immune cells and antibodies that are necessary to clear the virus,” Harrod noted. “While this can be uncomfortable, it is often a sign of an appropriate immune response that supports recovery.”
Not everyone has the same course when it comes to symptoms.
“Poor health, such as chronic lung disease, heart disease, and diabetes, is known to lead to a higher likelihood of severe infection,” Harrod added. “Immunocompromised individuals also are more susceptible.”
How flu spreads and what actually helps
Influenza mainly spreads through tiny droplets and aerosols that are expelled from the mouth or nose when a person coughs or sneezes. The virus can also transfer from shared surfaces to the eyes, nose, or mouth, making its ability to spread extremely efficient. People may spread the virus before they feel sick, and many indoor spaces put people in close contact where cleaning and ventilation are inconsistent.
“Crowded environments and shared spaces with poor ventilation and shared surfaces that are not disinfected make transmission much more likely,” explained Carlos Orihuela, Ph.D., professor in the Department of Microbiology.
Prevention works best in combination. If you are sick, avoid events, work, and school to reduce the number of people exposed. In crowded indoor settings, wear a well‑fitting mask. Wash your hands often and avoid touching your face to prevent the virus from entering through your eyes, nose, and mouth. Improve airflow where you can because fresher air dilutes the virus in the room.
“They all break the transmission cycle,” Orihuela emphasized. “Staying at home limits who might become exposed. Handwashing removes the virus from your hands. Ventilation clears or dilutes the virus from the air so that it is less likely to be inhaled.”
Flu vaccination still plays a role in protection. Influenza is a highly contagious, mutable virus that recurs each year. Being up to date with your vaccination lowers the risk of it escalating to something more serious.
“Sometimes there is a big mutation in the virus,” Orihuela noted. “In this case, a large segment of the population does not have protective antibodies, and this can lead to more cases of severe infection.”
When to act and why timing matters
Most people recover at home. In some cases, the infection can progress to pneumonia, making it hard for the lungs to deliver oxygen into the blood.
“Pneumonia is a very serious manifestation of severe influenza infection and is caused by the lungs becoming very ‘wet’ and unable to fully oxygenate the blood,” Harrod cautioned. “If treated early and oxygenation improves, the lung can clear the virus and repair.”
Experts suggest seeking care quickly for trouble breathing, chest pain, dehydration, a high fever that will not break, confusion, or signs of a secondary infection. This is especially important for people at higher risk.
Antiviral medicines such as oseltamivir (Tamiflu) and baloxavir (Xofluza) can shorten illness and reduce complications when started early.
“Antivirals such as Tamiflu and Xofluza are effective against influenza; however, they must be administered within 48 hours of infection onset to reach maximal efficacy,” Harrod said.
J. Victor Garcia-Martinez, Ph.D, chair of the Department of Microbiology, emphasized that antivirals can play a role not only in treatment but also in preventing further spread of influenza.
“Antivirals such as Xofluza, work by directly blocking a key step in influenza virus replication, which is why timing is so important,” Garcia-Martinez said. “When given early after exposure, Xofluza can markedly reduce the chance that a household contact becomes infected, and when administered to someone who already has flu, it lowers the amount of virus produced in the nose and throat—helping limit spread to others while also shortening illness for the patient. In simple terms, taking Xofluza quickly can help people recover faster and make it less likely they will pass the flu to family members or others living in close contact.”
Most flu cases get better with rest, fluids, and time. If breathing becomes difficult, a high fever persists, or hydration is a concern, do not wait to seek care. Simple steps taken early protect you and the people around you.