Treating Viral Infections
The immune system helps clear infections from the body. But sometimes it needs a little help.
Fortunately, there are drugs and other treatments for many viral infections. The ideal treatment would wipe out an infection altogether. But even when a cure is not available, a partially effective treatment may ease symptoms or even help you recover sooner.
The best approach for treating or managing an illness depends on the virus, the stage of the infection, and the person being treated. If you are sick or concerned about being infected, talk to a healthcare professional. They are trained in the available treatment options and can work with you to find a solution that is best for you.
Most drugs and treatments are aimed at one of three main targets: the virus, the immune system, or the symptoms. The descriptions below don’t cover everything, but they describe the most common options available.
The drugs and treatments described here are just some of the tools available for controlling outbreaks. Even better is to avoid getting infected in the first place. Important prevention strategies include physical distancing, masks, hand washing, sanitation, and vaccination.
Target: Virus
Antiviral Drugs
Most antiviral drugs prevent infected cells from making more viruses. They work by disrupting an essential step in the viral replication cycle. A few antiviral drugs block viruses from getting into cells.
Viruses use our own cells to replicate. That makes it hard to interfere with viral replication without also interrupting essential processes in healthy cells. In contrast, bacteria carry out their own essential processes, like copying genetic information and building proteins. Many antibiotic drugs work by disrupting these processes specifically in bacteria. Because bacteria are so different from people, the drugs do not cross-react with our own cells. But viruses rely on our cells to build viral proteins and often to copy their genetic information.
There are some viruses that use their own proteins to carry out key steps in their life cycles. And these proteins can be good drug targets. For example, some viruses use their own proteins to copy their genetic information. By targeting these viral proteins, scientists have been able to develop some antiviral drugs that are super effective and highly specific. Acyclovir is a drug that stops replication in herpesviruses. And several antiviral medications for treating HIV (a type of retrovirus) target specific viral proteins.
Another group of antiviral drugs works by getting between the virus and the host cell receptor. If a virus can’t attach, it can’t get in. Some of these drugs are designed to mimic viral proteins or host cell receptors.
Keep in mind that some treatments are also useful for prevention. For example PrEP (pre-exposure prophylaxis) is a drug regimen that decreases the chances of HIV infection.
Most antiviral drugs disrupt a step in a virus’s life cycle.
Through mutation, viruses can quickly develop resistance to single drugs. One strategy for getting around this is combination therapy—taking multiple drugs at the same time. This is common for HIV management. Another advantage is that each drug can be given at a lower, less-toxic dose. To learn more about mutation in viruses, visit How Viruses Evolve.
Antibodies attach to viruses, blocking them from locking on to the host cell.
Antibodies
Antibodies are one of the body’s natural defenses against infection. They are proteins, made by specialized immune cells, that circulate in the blood and other fluids. The body makes many types of antibodies, each with a specific target. When an antibody attaches to a virus, it blocks the virus from getting into cells and flags it for destruction. Antibody treatments, including the two described below, are based on these natural molecules.
Convalescent plasma is blood serum from a person who was infected and got better. It works because a person who has recently recovered still has large numbers of antibodies in their blood that are specific to the virus. This approach has been in use for more than 100 years, including during the 1918 influenza pandemic.
A newer technology for delivering antibodies to a patient is monoclonal antibodies. These antibodies are made from cells grown in a lab. The cells are genetically engineered to make a specific type of antibody. Most monoclonal antibodies are designed to fit with a specific virus. Others are more general and can be used with multiple types of infections.
Because viral replication is so intimately tied to a host cell, and because viruses are so diverse, it’s hard to find drugs that work against multiple types of viruses. That’s in contrast to “broad-spectrum” antibiotics that target many types of bacteria. Though there are a few broad-spectrum antiviral drugs, most are specific to a small group of related viruses, or even a single virus. And of course antibiotics don’t work against viruses at all—they’re specific to bacteria.
Target: The Immune System
The immune system is complicated. It’s made up of organs, cells, and molecules both large and small. Signaling molecules released from the site of infection travel in the bloodstream and throughout the body, with widespread effects. Yet scientists have learned a lot about how the immune system works. This knowledge has helped them to develop tools for monitoring its activity and drugs for steering its responses.
Activating the Immune System
With some viral infections, the immune system is slow to respond. Some viruses release molecules that suppress the immune system. Others have ways to hide out, evading detection. In cases like these, and especially in the early stages of infection, it can be useful to use drugs to get the immune system going. That way, the immune system can start fighting the infection sooner than it would on its own. Some drugs, for example interferons and cytokines, even mimic the body’s natural immune-boosting signals.
Vaccines are usually given to prevent infection, but some can also be used to treat people who have recently been infected. This strategy is especially useful for viruses that replicate slowly, like hepatitis B and rabies. The vaccine can prompt the immune system to start mounting a response that’s specific to the virus.
Suppressing the Immune System
Sometimes the immune system works a little too well. When tissues and cells sense an infection, they send out signaling molecules—including histamines, cytokines, and many others. Some of these molecules travel around the body, activating the immune system. They draw virus-fighting cells, which travel through the bloodstream, to the site of infection. But when immune signals get out of hand, they can do more harm than good. You may have heard of a “cytokine storm,” a complication that’s common in severe cases of COVID-19. Ironically, patients with the strongest immune systems are the most likely to develop this complication. That may be why the 1918 influenza pandemic was especially deadly among adults aged 20–40.
When immune-activating signals flood tissues, immune cells may start attacking healthy cells. Immune signals can also cause blood vessels to get leaky. At a low level, this can be helpful—it’s easier for immune cells to crawl out and go to the site of infection. But when blood vessels get too leaky, fluid can accumulate in the lungs or other organs and blood volume drops. Steroids and other immune-suppressing drugs can help during peak stages of infection—especially for fast-replicating viruses like influenza and SARS-CoV-2. They can calm the immune system and decrease the concentration of signaling molecules locally and around the body. The immune system still fights the infection, but without doing as much harm to healthy tissues.
A good immune response is just right—not too big and not too small. The right drugs delivered at the right time can nudge the immune system toward a better balance.
Target: Symptoms
Another category of treatments is aimed at relieving symptoms while the immune system works on clearing the virus. This category is very broad. It includes home remedies, medical interventions that are usually delivered at hospitals, and emotional support. Some of these treatments are directed at the specific effects of a virus. Others are more generally useful for overall health and wellness.
Treatments delivered in hospitals can include things like IV fluids, electrolytes, blood transfusions, supplemental oxygen, ventilator support, and dialysis for filtering harmful molecules from the blood. The goal is to keep the patient as healthy and comfortable as possible while their body deals with the infection.
Some illnesses can be managed at home but severe symptoms are best treated in a hospital.
Medicines can be useful too—including drugs for fever reduction, nausea control, antibiotics to prevent or treat secondary bacterial infections, and many others.
Your immune system works best when your stress levels are low. So when you’re sick it’s helpful to get plenty of sleep and try to avoid stress. Often the best place to do that is at home. And there are plenty of options here for symptom relief too. Soup, hot tea, or a steamy shower may help you feel better. Honey can soothe a sore throat. Practicing a familiar ritual, eating a favorite meal, or having someone care for you can be deeply comforting.
References
De Clercq, E., & Li, G. (2016). Approved antiviral drugs over the past 50 years. Clinical microbiology reviews, 29(3), 695-747.
Ison, M. G. (2017). Antiviral treatments. Clinics in chest medicine, 38(1), 139-153.
Kaufmann, S. H., Dorhoi, A., Hotchkiss, R. S., & Bartenschlager, R. (2018). Host-directed therapies for bacterial and viral infections. Nature Reviews Drug Discovery, 17(1), 35.
Marson, P., Cozza, A., & De Silvestro, G. (2020). The true historical origin of convalescent plasma therapy. Transfusion and Apheresis Science.
Murray, P., Rosenthal, Ken S., & Pfaller, Michael A. (2020). Chapter 40, Antiviral agents and infection control. Medical microbiology (Ninth ed.).
Wong, J. P., Viswanathan, S., Wang, M., Sun, L. Q., Clark, G. C., & D'elia, R. V. (2017). Current and future developments in the treatment of virus-induced hypercytokinemia. Future Medicinal Chemistry, 9(2), 169-178.