How long does glandular fever last? Recovery by phase and when you train again

How long glandular fever lasts depends on which phase you mean. The acute complaints, so fever, sore throat and swollen glands, usually run two to three weeks. The fatigue that follows lasts two to three months according to the Dutch public health institute RIVM. Contact sport runs on a separate clock.

That last sentence is where most Dutch pages stop explaining.

Thuisarts, the Dutch GP-backed patient site, writes that you are best off keeping to your normal day as much as possible, sport included. That holds for your job, your school and your walk. For judo, football and rugby it is different, and that difference is worth knowing.

How long does the acute phase last?

Usually two to three weeks. Fever often settles first, the sore throat follows, and the swollen glands in your neck stay noticeable a while longer. Then comes the phase where you are officially better but get nothing done, and that one lasts longest.

The incubation period sits ahead of all that.

RIVM puts it at 4 days in young children up to 8 weeks in young adults. So you cannot possibly work backwards to who infected you. For many people that is a disappointing but freeing fact.

When can you train again after glandular fever?

For ordinary exertion: as soon as you feel up to it, building gradually. For contact and collision sport there is an extra threshold of at least three to four weeks from symptom onset, because the spleen can be enlarged and is then more vulnerable. That distinction is the heart of it.

It concerns a rare but serious risk.

The American Medical Society for Sports Medicine sets out exactly this separation between ordinary and contact sport in its position statement on mononucleosis and athletic participation (PMID 37186809). Sylvester and colleagues analysed the splenic rupture cases and found that nearly all of them occurred in the first weeks (PMID 31550435).

Imagine a footballer of 22 with symptoms since 1 March. By mid-March he can walk easily and by late March cycle lightly. Only after three to four weeks does he return to contact drills. His easy run comes back sooner than his match.

How long do you stay infectious?

Longer than most people expect. RIVM describes viral shedding from about a week after infection for a long period, sometimes up to 18 months afterwards. Isolating therefore achieves little and is not done in practice.

That long window changes nothing about what to do.

Since nearly everyone eventually picks the virus up, staying home is not a strategy. You stay home because you are ill, not to protect others.

Why does the fatigue last so long?

Because the infection makes heavy demands on your immune system and recovering from that runs slower than clearing a fever. RIVM gives two to three months as the ordinary course. If it runs on beyond that, the conversation shifts to persistent complaints after infection.

The figures on that are more reassuring than their reputation.

In a cohort of 301 adolescents after glandular fever, 13 percent met chronic fatigue criteria at six months, 7 percent at one year and 4 percent at two years (PMID 19564299). So the series falls sharply. What happens in that tail is in long-term effects.

How do you build back sensibly?

By feel, with resting heart rate as the brake. Take your usual morning figure as a reference and keep sessions short while it is still clearly raised. As it heads back toward your old level, raise duration before you raise intensity.

Duration first, intensity after. Always in that order.

There is one pattern to recognise: a worsening that only arrives a day later and is out of proportion to the effort. That is not normal training fatigue and it calls for backing off rather than pushing on. See post-exertional malaise.

How to track that build with data is in resting heart rate and HRV values by age. If tiredness is unchanged after three months, ruling out other causes is a logical step, with values like ferritin and TSH in the 360 health panel. The broader overview is in blood test for fatigue.

My advice: keep the contact-sport pause even when you feel fine, and discuss the moment of return with your GP.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.

References

• Putukian M, O'Connor FG, Stricker P, et al. American Medical Society for Sports Medicine position statement: mononucleosis and athletic participation. Clinical Journal of Sport Medicine, 2023. PMID 37186809.
• Sylvester JE, Buchanan BK, Paradise SL, Yauger JJ, Beutler AI. Association of splenic rupture and infectious mononucleosis: a retrospective analysis and review of return-to-play recommendations. Sports Health, 2019;11(6):543-549. PMID 31550435.
• Katz BZ, Shiraishi Y, Mears CJ, Binns HJ, Taylor R. Chronic fatigue syndrome after infectious mononucleosis in adolescents. Pediatrics, 2009;124(1):189-93. PMID 19564299.
• RIVM. Glandular fever (ziekte van Pfeiffer), questions and answers.
• Thuisarts.nl. I have glandular fever (Ik heb de ziekte van Pfeiffer).