COVID-19:
Acute Illness, Treatment & Antiviral Therapy

1. What is COVID-19?

COVID-19 is the illness caused by the coronavirus SARS-CoV-2. The virus did not disappear when the pandemic ended; it now circulates permanently in the population — experts describe this as an endemic situation with seasonal waves, similar to flu or RSV.^¹

The decisive difference from 2020: almost everyone has by now built up some basic immunity, through vaccination, past infections or both. That is why an infection today usually runs a far milder course than in the first years of the pandemic. This does not make COVID-19 harmless — for older people and for people with a weakened immune system the infection can still become dangerous, and it is precisely for these groups that effective antiviral medicines now exist.

2. How the illness runs today, and which variants circulate

Since the end of 2021 all circulating virus variants have descended from the Omicron line. These descendants keep changing, but they differ little from one another in the way the illness runs: they mainly affect the upper airways and reach the lungs less often than earlier variants did.^¹ Broadly, four courses can be distinguished:

• Asymptomatic: The infection is not noticed at all — at most it shows up through a test taken by chance.
• Mild illness: The most common case. Symptoms like a cold or a mild bout of flu, recovery within roughly one to two weeks, no breathlessness.
• Moderate to severe illness: The virus reaches the lungs, breathlessness sets in and oxygen levels fall — this belongs in medical hands, often in hospital.
• Critical illness: Intensive care is needed. This is rare today and affects mainly very old or immunocompromised people.

A typical mild illness starts one to four days after infection with a scratchy throat and fatigue, peaks after two to three days and then slowly settles. Cough and exhaustion can linger for another one to two weeks even after a mild course — on its own, that is not yet Long COVID.

3. Symptoms and who is at higher risk

Typical symptoms

• Sore throat and a runny nose — with the current variants often the first and leading symptoms.
• Cough — usually dry, and it may build up over several days.
• Fever and aching limbs — from a slightly raised temperature to a high fever.
• Headache and marked exhaustion — often out of proportion to what a common cold would cause.
• Loss of smell and taste — the former hallmark symptom has become considerably less common with today’s variants, but it still occurs.
• Stomach and bowel symptoms — nausea or diarrhoea, especially in children.

Symptoms alone cannot reliably tell COVID-19 apart from flu, RSV or a common cold — that needs a test. The guide Cold, flu or COVID? offers help with that decision during the winter months.

Who is at higher risk

For the great majority of healthy adults, COVID-19 is now something you get through without much trouble. A higher risk of severe illness applies above all to:^¹

• People from around the age of 60 — the risk rises markedly with age.
• People with a weakened immune system — because of an illness or of medicines that suppress the immune response.
• People with chronic conditions — for example diabetes, COPD, heart failure, chronic kidney or liver disease, or severe obesity.
• Pregnant women — particularly in the last third of pregnancy.

This classification is more than statistics: it decides whether antiviral treatment should be considered when an infection occurs — and for that, every day counts (more on this in section 7).

4. How it spreads and what raises the risk

SARS-CoV-2 spreads mainly through droplets and aerosols — the finest suspended particles produced when we breathe, speak, sing and cough. In closed, poorly ventilated rooms aerosols build up, which is why most infections happen indoors. The time between infection and first symptoms (the incubation period) is usually only one to four days with the current variants. As a rule you are already infectious shortly before symptoms begin, and most infectious during the first days of the illness.^¹

Whether an infection turns severe depends not only on age and pre-existing conditions but also on medicines that dampen the immune system:

5. Diagnosis: self-test, antigen test, PCR

The diagnosis today almost always rests on rapid antigen tests or a PCR test:^²

• Antigen self-test: For use at home, with a result in 15 to 30 minutes. It mainly detects an infection when the viral load is high — during the first one to two days of symptoms it can still be negative despite an infection.
• Repeat testing: If the suspicion remains, repeat the self-test after 24 to 48 hours — many infections only become visible on the second attempt.
• PCR test: Considerably more sensitive; it is carried out at the practice or in a laboratory. It makes sense whenever the result has consequences — above all when antiviral treatment is being considered.
• No routine imaging: A chest X-ray or CT scan is only needed if severe illness is suspected.

6. Treating mild illness

For healthy adults without risk factors the rule is simple: COVID-19 is treated like any other respiratory infection — symptomatically, with rest and patience. An antiviral is usually not needed here according to the guideline, because the immune system controls the infection itself.^³

7. Antiviral therapy: Paxlovid and its interactions

For people at higher risk there are antiviral medicines that slow down viral replication and have been shown to reduce the risk of hospital admission. The most important one is nirmatrelvir/ritonavir (brand name Paxlovid) — tablets taken over five days.^³,⁴ For the treatment to work it has to start within five days of symptom onset; the earlier, the better.

It is usually an option for adults with mild to moderate illness who are at increased risk of a severe course — that is, the groups listed in section 3. Whether it makes sense in an individual case is decided by the treating practice. For selected situations remdesivir is available as an infusion instead; molnupiravir was not granted a marketing authorisation in the EU.^³

The catch: major drug interactions

The ritonavir component of Paxlovid blocks a central metabolising enzyme in the liver (CYP3A4). That is intentional — it keeps blood levels of the actual antiviral high. But it also means that many long-term medicines are suddenly broken down more slowly and can build up in the body, sometimes to dangerous levels. The very people Paxlovid is meant for — older patients and those with chronic conditions — often take several of these medicines.^⁴

This table is only an excerpt — the product information lists well over a hundred relevant combinations.^⁴ That is why a complete list of your medicines belongs on the table before any prescription, including over-the-counter products such as St John’s wort (which can weaken the effect of Paxlovid). The guide Keeping a medication list shows how to put such a list together; the background to interactions is explained in Drug interactions.

What else you should know about Paxlovid

• Side effects: The most common are a bitter, metallic taste, diarrhoea and nausea — usually mild and settling after the course ends.
• Reduced kidney function: With moderate impairment the dose is reduced; with severe impairment Paxlovid is not recommended — kidney values are part of the prescribing decision.
• Rebound: In some of those treated, symptoms or a positive test flare up again briefly after the course ends — this is usually harmless and not a reason to start a second course on your own.

8. When to go to hospital

Most people can get over the illness at home. But there are warning signs you should not wait out:

• Breathlessness or shortness of breath at rest — even speaking or walking a few steps is an effort.
• Falling oxygen saturation — if you own a pulse oximeter: readings that stay well below your own normal range are an alarm sign and need medical assessment.
• Persistently high fever — over several days despite fever-reducing medicines, or a fever that returns after you had started to improve.
• Chest pain, palpitations, confusion or unusual drowsiness.
• Signs of dehydration — barely drinking or passing urine, especially in older people.

In hospital further treatments are available — from oxygen and anticoagulation to anti-inflammatory medicines such as dexamethasone. These treatments belong in the clinic and nowhere else.^³

9. Telling it apart: Long COVID

If symptoms persist for more than four weeks after the infection or appear newly, this is called Long COVID; from three months onwards, post-COVID syndrome. Typical features are persistent exhaustion, problems with concentration (“brain fog”), intolerance of exertion and shortness of breath. One point matters for putting this in perspective: feeling tired and run down for one to two weeks after the infection is normal and is not yet Long COVID. But if you are still clearly below your usual level after weeks, or if your symptoms reliably worsen after exertion, read on in the article Long COVID and speak to your GP practice.

10. Vaccination: what is recommended in Germany

COVID-19 vaccination mainly protects against severe illness — protection against catching the virus at all is limited and wanes over time. In Germany, the Standing Committee on Vaccination (STIKO) currently recommends basic immunity built from several antigen contacts for all adults, plus annual booster vaccinations in autumn for people aged 60 and over, for people with underlying conditions or a weakened immune system, for residents of care homes and for healthcare staff.^⁵ The booster can easily be combined with the flu vaccination at the same appointment. Which other vaccinations are due for you is covered in the guide Vaccinations for adults.

11. Everyday life: recovering and easing back in

• Stay at home while you are ill — there is no longer a legal duty to isolate in Germany; at least three to five days of rest and reduced contact are recommended.
• Wear a mask when contact cannot be avoided — especially around older or immunocompromised people, including in the days after your symptoms have settled.
• Sport only after you have recovered — no training while you have a fever or feel unwell, and afterwards build back up slowly over one to two weeks. If you get chest pain or palpitations on exertion, have it checked medically.
• Keep taking your regular medication — blood pressure tablets, blood thinners and the rest carry on as normal unless your practice decides otherwise. The guide How to take medications has the details.
• Keep a record of how it goes — note your temperature, your symptoms and the medicines you take. If things do get worse, your practice has the full picture straight away.

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