Understanding and Managing Post-Viral Fatigue

What is Post-Infection Fatigue?

Post-infection fatigue is defined quite simply as an unusual and long-lasting level of fatigue that starts with an infection of some kind, but goes on long after the infection is gone.

Definitions are remarkably similar both in different countries, and from professional or lay sources (see box).

Definitions of post-infection and post-viral fatigue

“Post-viral fatigue refers to lingering feelings of extreme tiredness after a viral illness.”
Healthline.com

“[Post-viral fatigue is]…persistent exhaustion which some people experience after recovering from other kinds of infection.”
David Cox in an article on the BBC website

“Post-viral fatigue is when the fatigue that started with a viral infection continues for a longer period of time after the infection has gone.”
Guide to managing post-viral fatigue published by North Bristol NHS Trust.

Despite the consensus on its definition, we actually know remarkably little about post-infection fatigue.

However, that is starting to change. Long COVID has opened the door for more research on the whole issue of post-infection fatigue, and doctors are starting to understand more about it, and particularly how to manage it.

When Do People Develop Post-Infection Fatigue?

Post-infection fatigue is thought to be most common following a viral infection—but that is probably because the most common form of infection is from viruses.

Long COVID has highlighted this issue in recent years. However, it can also occur after other viral infections such as flu and Epstein-Barr virus, and also from other infections such as the tick-borne condition Lyme disease. Indeed, doctors think that almost any infection can trigger post-infection fatigue—but they do not really know why it happens to some people and not others.

What we do know is that:

Post-infection fatigue is not related to your level of fitness before getting the infection. Extremely fit people have developed post-viral fatigue—but so have people who seldom exercise.
It is not related to the severity of the infection. It is possible to have a very mild infection but then develop post-viral fatigue, and it is also possible to be really quite unwell and then recover quickly.
It is not related to age. Children, working-age adults and older people may all develop post-infection fatigue.
The duration is very variable. It is most likely to last a few months, but may go away more quickly, or last longer.

Researchers have suggested several different reasons why post-infection fatigue may occur. These include viruses hijacking the mitochondria, the ‘energy powerhouses’ of every cell in the body, an unhelpful immune response akin to an autoimmune condition, and problems clearing waste from cells. It is entirely possible that all of these may be involved, either in the same person, or varying between individuals.

However, the research is still at a very early stage. The real question is not so much why post-infection fatigue is occurring, as what causes the ‘incorrect’ response in the first place, and whether it can be prevented or treated. The jury is definitely still out on that, but current thinking suggests that personalised treatment may be necessary in future.

Post-viral fatigue vs. chronic fatigue syndrome/myalgic encephalitis (CFS/ME)

One term that often comes up when talking about or searching for information on post-infection fatigue is chronic fatigue syndrome or myalgic encephalitis (CFS/ME). The two are not considered to be medically exactly the same. However, they have very similar symptoms: chronic tiredness, aches and pains, and brain fog. The key difference is that post-viral fatigue follows an infection. In other words, if there is an obvious trigger, the immediate diagnosis is likely to be post-infection fatigue.

This may later develop into CFS/ME, which is a chronic condition that can last much longer—often years. CFS/ME may also develop ‘out of the blue’, without an obvious trigger. The fatigue is also often much greater in CFS/ME. If there is no obvious trigger, or the symptoms go on for a long time, and the fatigue is very severe, the diagnosis is more likely to be ‘upgraded’ to CFS/ME.

It is important to note that the initial response and suggestions for management are the same. However, CFS/ME may require other treatment to manage the symptoms or deal with any underlying infectious agent before graded exercise or pacing will be helpful.

Managing Post-Infection Fatigue

The first stage of managing post-infection fatigue is actually to manage your fatigue and activity while you have an infection.

It is really important to rest when you are ill, as this gives your body the best chance of recovering without developing post-infection fatigue. This means resting both mentally and physically—so trying to avoid work, checking emails, using social media, or anything that requires you to think very much. That said, don’t just lie around. Moving gently is good, even it is only around your bedroom or living room.

The second stage is to give yourself time to recover.

It is also worth saying that you should give yourself time to recover. It is tempting to rush back to work or into activity the moment you can get out of bed. However, this is not helpful, because it does not give your body enough time to recover fully—and is likely to mean that you take longer to recover even if you do not develop post-infection fatigue. It can be several weeks post-infection before you feel fully ‘back to normal’, so don’t rush things.

If you still don’t feel better—or still feel very fatigued—about six to eight weeks after having an infection, it is worth talking to your doctor.

They may wish to carry out tests to identify if there is an underlying problem, because many conditions can cause fatigue. Only once everything else has been ruled out are you likely to be given a diagnosis of post-infection fatigue.

Once you have reached that stage, there are various strategies and tips that are recommended.

These include:

Try some activity. The general recommendation is to try doing some exercise or activity. Keep it gentle, and don’t try to do too much in one go. A walk round the block or even just the garden might be enough to start with.
Increase your activity very slowly. Once you have discovered what is possible without being totally exhausted, you can very slowly start to increase what you try each day or every other day. This increase might be in intensity or time—but ‘slowly’ is the key term. This is not like doing a programme such as ‘Couch to 5k’. If you are able to walk a mile today, try walking 1.1 miles tomorrow, not 2 miles—and definitely not running. Take things gently.
Don’t be tempted to do too much. It is easy to think that you will just ‘try it’ this once, and see what happens if you try doing a lot more—but don’t. It will exhaust you completely, and set back your recovery.
However, keep gently increasing the exercise. There will be days when you really don’t want to do anything—but it is important to keep going with the exercise unless there is an obvious reason why you might be more tired than usual. Try to develop a routine for exercise and keep going with it.
Remember that thinking uses energy too. You will probably find that you don’t have much energy for work, even if you have a sedentary job. Intellectual work is tiring too, and you need to pace yourself with that as well as physical activity.
Rest when you need it. You will probably find that you need to take more rest than usual, and quite possibly nap during the day. This might mean getting accommodations from work or school to enable this, which may require a doctor’s note.
Remember to have some fun. You may feel that you need all your energy just to work and take gentle exercise, but it is important to have fun too. Make time for friends or doing something you enjoy—but preferably low energy.
Manage your own and others’ expectations. You need to be realistic about what you can do—and that it will be much less than before you were ill. This may need spelling out to other people, even close family, and realistically, both you and they will forget sometimes. Try not to fall into a cycle of ‘boom and bust’ where you do too much and then need several days to recover. Instead, it is better to keep going gently at more or less the same pace.
There is more about how to go about managing expectations in our pages on Managing Your Own Expectations, and Managing Other People’s Expectations.
Try pacing your activities. It may be helpful to plan your activities over several days, to allow you to ‘pace’ yourself. For example, if you know that you have some work to do, but you also need to get some chores done, you might plan to do the work one day, and then the chores the next, so that you are not too tired when you have finished. If you have three chores to do, you might spread them over three days.
Make sure that you look after yourself. This includes getting plenty of sleep—and fatigue can both make it harder to sleep, and mean that you need to sleep much more—and eating a healthy diet.
There is more about these issues in our pages on What is Sleep? and Food, Diet and Nutrition.

Takeaways, ready meals, supplements and fatigue

When you are tired all the time, it is tempting to turn to ready meals or takeaways for an easy meal. However, this is likely to be problematic, because it will probably mean that you are eating a lot of ultra-processed food. This can negatively affect both physical health and mood. Instead, it is better to eat simple, easy-to-prepare meals, with plenty of fresh fruit and vegetables.

It may also be tempting to think that you could supplement a poor diet by taking vitamins or another supplement. However, as our page on Dietary Supplements explains, supplements should only be taken when a clear deficiency has been identified by a doctor. Otherwise, they may actually be harmful—and there is certainly no supplement that has been identified that provides a miracle cure for post-infection fatigue.

A Final Message

As you start to feel less tired all the time—and you almost certainly will do so eventually—it is tempting to launch yourself straight back into much more activity.

Don’t.

Instead, keep taking things slowly.

Your motto should be ‘Get better slowly’. Don’t rush things or try to do too much at once. Instead, give yourself time to recover fully, and don’t push yourself too far until you feel fully recovered.

Continue to:
Stress and Stress Management
Avoiding Burnout