How long is someone infectious after a viral infection?

How long is someone infectious after a viral infection?
How long is someone infectious after a viral infection?


[Original article on NHS Choices website]

The length of time you’re infectious for after having a viral infection depends on the type of virus involved. The infectious period often begins before you start to feel unwell or notice a rash.

The infectious periods for some common viral infections are described below.


The length of time that bronchitis is infectious varies, depending on its cause. In most cases, bronchitis is caused by the same viruses that cause the common cold or flu and you’re likely to be infectious as long as you have cold or flu symptoms.


Chickenpox is infectious from about one to two days before the rash appears until all the blisters have fully crusted or scabbed over. This is usually five to six days after the start of the rash.

Common cold

The common cold is infectious from a few days before your symptoms appear until all of the symptoms are gone. Most people will be infectious for around two weeks.

Symptoms are usually worse during the first two to three days and this is when you’re most likely to spread the virus.

Flu (influenza)

Flu is usually most infectious from the day your symptoms start and for a further three to seven days. Children and people with lowered immune systems may be infectious for a few days longer.

Glandular fever

Glandular fever is infectious during the incubation period (the time between catching the virus and developing the symptoms). For glandular fever, this can be two to four weeks.

Some people have the virus in their saliva for a few months after recovering from glandular fever, and may continue to have the virus in their saliva on and off for years. However, glandular fever isn’t very infectious and the length of time people remain infectious varies considerably.


Symptoms of measles appear around 10 days after you become infected. Measles is most infectious after the first symptoms appear and before the rash develops.

First symptoms of measles include:

a high temperature
red eyes
sensitivity to light
cold-like symptoms – such as a runny nose, watery eyes, swollen eyelids and sneezing

Around two to four days later, a red-brown spotty rash develops that normally fades after about a week.


Mumps causes your salivary glands to swell. These glands are just below and in front of your ears. Mumps is most infectious from a few days before your glands swell until a few days afterwards.

Rubella (German measles)

Rubella is infectious for one week before the rash appears and for up to four days afterwards.

You should stay away from school or work for six days after the rash starts to avoid infecting others and try to avoid contact with pregnant women during this time.


Shingles is infectious from when the rash first appears until the last blister has scabbed over. This is usually after about 10-14 days.


Tonsillitis itself isn’t contagious but the viruses that cause it are. The length of time you’re infectious will depend on the virus. Read more on the causes of tonsillitis.

Fatigue – 10 medical reasons for feeling tired

Treatments for Fatigue

Any serious illness, especially painful ones, can make you tired. But some quite minor illnesses can also leave you feeling washed out. Here are 10 health conditions that are known to cause fatigue.

1. Coeliac disease

This is a type of food intolerance, where your body reacts badly when you eat gluten – a substance found in bread, cakes and cereals. One in 100 people in the UK are affected, but research suggests that up to 90% of them don’t know they have the condition, according to patient group Coeliac UK. Other symptoms of coeliac disease, apart from tiredness, are diarrhoea, anaemia and weight loss. Your GP can check if you have coeliac disease through a blood test.

Read more about coeliac disease.

2. Anaemia

One of the most common medical reasons for feeling constantly run down is iron deficiency anaemia. It affects around one in 20 men and post-menopausal women, but may be even more common in women who are still having periods.

Typically, you’ll feel you can’t be bothered to do anything, your muscles will feel heavy and you’ll get tired very quickly. Women with heavy periods and pregnant women are especially prone to anaemia.

Read more about iron deficiency anaemia.

3. Chronic fatigue syndrome

Chronic fatigue syndrome (also called myalgic encephalomyelitis or ME) is a severe and disabling tiredness that goes on for at least six months. There are usually other symptoms, such as a sore throat, muscle or joint pain and headache.

Read more about chronic fatigue syndrome.

4. Sleep apnoea

Sleep apnoea is a condition where your throat narrows or closes during sleep and repeatedly interrupts your breathing. This results in bad snoring and a drop in your blood’s oxygen levels. The difficulty in breathing means that you wake up often in the night, and feel exhausted the next day.

It’s most common in overweight, middle-aged men. Drinking alcohol and smoking makes it worse.

Read more about sleep apnoea.

5. Underactive thyroid

An underactive thyroid gland means that you have too little thyroid hormone (thyroxine) in your body. This makes you feel tired. You’re also likely to put on weight and have aching muscles. It’s most common in women, and it happens more often as you get older.

Your GP can diagnose an underactive thyroid by taking a blood test.

Read more about having an underactive thyroid.

6. Diabetes

One of the main symptoms of diabetes, a long-term condition caused by too much sugar in the blood, is feeling very tired. The other key symptoms are feeling very thirsty, going to the toilet a lot and weight loss. Your GP can diagnose diabetes with a blood test.

Read more about diabetes and find out how to make smart sugar swaps.

Find your local diabetes support services.

7. Glandular fever

Glandular fever is a common viral infection that causes fatigue, along with fever, sore throat and swollen glands. Most cases happen in teenagers and young adults. Symptoms usually clear up within four to six weeks, but the fatigue can linger for several more months.

Read more about glandular fever.

8. Depression

As well as making you feel very sad, depression can also make you feel drained of energy. It can stop you falling asleep or cause you to wake up early in the morning, which makes you feel more tired during the day.

Read more about depression.

Find your local depression support services and your local depression self-help groups.

9. Restless legs

This is when you get uncomfortable sensations in your legs, which keep you awake at night. You might have an overwhelming urge to keep moving your legs, a deep ache in your legs, or your legs might jerk spontaneously through the night. Whatever your symptoms, your sleep will be disrupted and of poor quality, so you’ll feel very tired throughout the day.

Read more about restless legs.

10. Anxiety

Feeling anxious is sometimes perfectly normal. However, some people have constant, uncontrollable feelings of anxiety, which are so strong they affect their daily life. Doctors call this generalised anxiety disorder (GAD). It affects around around one in 20 people in the UK. As well as feeling worried and irritable, people with GAD often feel tired.

Read more about anxiety.

Find your local anxiety support services.



This video may be of interest

Glandular fever! What is glandular fever and what are your experiences with glandular fever? And more on the Epstein-Barr virus

Glandular Fever
Glandular Fever

“Your glands are up!”

How many of us can remember that phrase from our childhoods.  Indeed in each year, according to the UK’s National Health Service 1 in 200 people will contract glandular fever.  That being said, most people who get glandular fever are in their late teens and early twenties.

When I was at school one of my fellow students had a bout of glandular fever resulting in weeks if not months off sick.

So I felt that it could well be useful to produce a brief guide to glandular fever as part of our series of informational blogs.  As with all our blogs your participation is most welcome.  It would be great to hear about your experiences of glandular fever and its impact upon your life and health.  This will, we hope, provide support for others in a similar situation.

The majority of people who develop glandular fever do so in a period of around two months after contracting the Epstein-Barr virus.  This is perhaps the most common virus which has been covered in a previous blog here  I think the comments section is of particular value.

The main symptoms  of glandular fever are:-

1)                       Fever.  As the name suggests of course.  In this case it is likely to be over 38ºC or                           100.4ºF (in old money).

2)                       Swollen nodes or glands in the neck.  Hence the name glandular fever.

3)                       Sore throat.

4)                       Fatigue.  You can read more about the impact of fatigue by checking out our recent patient experience blog.

In some cases there are a number of rarer symptoms.  These can include jaundice and swollen adenoids.  Jaundice is more common with people in the older age brackets who contract glandular fever.

Normally the infection lasts about two or three weeks, starting to get better after around one week albeit slowly.  That being said the fatigue may last for up to six months after the other symptoms have disappeared.

In milder forms of the fever treatments are normally painkillers which also help fight the inflammation.  In more serious cases hospitalisation may be required.

It is worth noting that there does seem to be a link between Epstein–Barr viral infection and contracting a number autoimmune conditions and other illnesses.   In particular Parkinson’s disease,  Lupus (, rheumatoid arthritis (, and multiple sclerosis (

So over to you.  We are always really interested in the experiences of our readers of their medical conditions.  It would be great if you could share your glandular fever story in the comments box below.

You might care to consider the following questions while sharing your story:-

a)                        At what age did you develop glandular fever?

b)                       What were your symptoms?

c)                       Do you know what the cause was?

d)                       How you were treated and how successful were the treatments?

e)                       Finally, if you contracted the Epstein–Barr virus did you have any complications afterwards such as an autoimmune condition?

Please just think of these questions as a guideline.  It would be great if you could share anything you think may be of interest about glandular fever.

Thanks very much in advance.