Measles - What is Measles?
Measles is a highly infectious viral illness. It is common among children but may affect people of all age groups. Measles, like most other viral ailments, may have a benign course with few complications other than fever and a rash. However, in special vulnerable populations like malnourished children and those with a diminished immunity this can lead to serious complications including death.
Measles is rare these days due to effectiveness of the Measles vaccine given in the combined shot of MMR vaccine (Measles, Mumps and Rubella).
This thin-section transmission electron micrograph (TEM) revealed the ultrastructural appearance of a single virus particle, or "virion", of measles virus. The measles virus is a paramyxovirus, of the genus Morbillivirus. It is 100-200 nm in diameter, with a core of single-stranded RNA, and is closely related to the rinderpest and canine distemper viruses. Two membrane envelope proteins are important in pathogenesis. They are the F (fusion) protein, which is responsible for fusion of virus and host cell membranes, viral penetration, and hemolysis, and the H (hemagglutinin) protein, which is responsible for adsorption of virus to cells.
Transmission of measles
Measles can occur at all ages but children between the ages of 1 and 4 are most at risk. The virus is spread via millions of tiny droplets that are sneezed or coughed out by an infected person. Persons around who breathe in the droplets with the virus can catch the infection. Infection can also be spread when objects contaminated with the droplets are touched and the hands are brought near the nose of mouth.
Symptoms of measles
The initial symptoms of measles are much like a common cold of flu. There is high fever, red and runny eyes and nose and a characteristic rash. There are greyish white spots in the mouth and throat.
After a few days a red-brown spotty rash will appear all over the body. This starts behind the ears commonly and spreads around the head and neck before spreading to the legs and the whole body.
Risks associated with measles
Measles is a notifiable disease. This means that any doctor who diagnoses the infection must inform the local health authority in order to identify the source of the infection to stop it from spreading further.
Complications of measles include pneumonia, meningitis and even death.
Pregnant mothers who contract measles may be at a serious risk of transmitting the infection to the child. Several congenital abnormalities may occur in the unborn baby is exposed to the infection before birth. Measles in pregnancy can cause miscarriage, premature labour or a baby with low birth weight.
Treatment of measles
There is no specific treatment for measles since it is a viral illness that resolves on its own. An infected person, however, needs supportive care like use of fever reducing medications (Paracetamol/Acetaminophen) and plenty of fluids.
Prevention of measles
The best way to prevent measles is to vaccinate the child. Commonly the first dose of measles, mumps and rubella (MMR) vaccine is given when the child is around 13 months old. A booster is given before the child starts school.
Measles vaccine cannot be given to pregnant mothers but all women intending to become pregnant must be vaccinated against the virus.
Measles statistics
Measles is still the leading cause of vaccine-preventable childhood mortality in the world. In the UK, vaccine uptake rates for measles, mumps and rubella (MMR) in children aged two reached 90% in the first quarter of 2011. The number of people with confirmed measles in England and Wales between January and August 2011 was 836. In the USA, measles has been virtually eradicated since 2002.
Measles infection takes around 10 days to manifest as apparent symptoms. The symptoms may last for around 2 weeks before finally resolving on their own. The measles rash usually appears a few days afterwards.
Initial symptoms
Symptoms of measles infection in its initial phases include:-
Influenza or common cold like symptoms including runny nose, watery eyes, sneezing etc.
There are swollen eyes and eyelids and the eyes are red and sensitive to light as well. This is known as conjunctivitis.
There may be a mild to severe rise of temperature. Peaks may be over 40.6C (105F) especially in children and peaks keep occurring for several days. The temperature normalizes only to rise again when the rash appears
Weakness, irritability and refusal to eat in a child
Muscle pain and aches
Dry cough
Koplik's spots
Small pin-head size greyish-white spots (called Koplik's spots) in the mouth and throat. These develop within two days of appearance of symptoms. These may develop on the inside lining of the cheeks, so they are difficult to see.
The spots typically occur opposite the second molar teeth as small, red spots, each with a bluish-white speck in the centre. They occur in 60-70% of patients during the initial phase and remain up to 2-3 days after the rash disappears.
The measles rash
These are reddish brown spots. The measles rash appears two to four days after initial symptoms and lasts for up to eight days. The rash usually starts behind the ears, spread around the head and neck, then spreads to the legs and the rest of the body.
The spots are small and distinct initially but soon get bigger and join together. At later stages the rash becomes blotchy and confluent. It fades after three to four days and may peel off after a week or so. It leaves behind a brownish discoloration, sometimes accompanied by fine peel-offs.
There may be nausea and vomiting, abdominal pain and diarrhoea.
Complications of measles
In most cases the measles infection passes without severe complications. In some children however there may development of complications. These complications may be debilitating or even life threatening. These include:-
Ear infections otitis media
Lung infections – pneumonia
Liver infections – hepatitis
Eye inflammation – Conjunctivitis
Inflammation of the brain – encephalitis. This is very rare and may develop a few days after the rash has appeared, and a quarter of those who get this complication will be left with brain damage. A devastating but extremely rare progressive illness called subacute sclerosing panencephalitis (SSPE) may occur many years after the first episode of measles and is usually fatal. It is rare and affects less than one in 100,000 cases.
Complications involving the nervous system
Measles Causes
Measles is caused by infection with the rubeola virus. This is a highly infectious virus spread by airborne droplets from an infected person.
The measles virus
The measles virus is a paramyxovirus belonging to the genus Morbillivirus. The virus is 100–200 nm in diameter and has a core of a single stranded RNA. The virus is closely similar to other viruses like rinderpest and canine distemper viruses.
It has two membrane envelope proteins that are important for pathogenesis of measles in humans. These proteins are the F (fusion) proteins that are responsible for fusion of virus and host cell membranes. This fusion further leads to penetration of the virus and eventually breakdown of the RBCs (hemolysis) in the host.
There is also the H (hemagglutinin) protein that helps the virus to be adsorbed into the host cell. As an antigen there is a single type of measles virus. The H glycoprotein, may have some amount of variability but this does not cause changes in the virus or affect the efficacy of the measles vaccine that works against it.
The measles virus remains a delicate virus and is rapidly inactivated by heat, light, acidic pH and by chemicals and enzymes such as ether and trypsin. It can survive for less than 2 hours in the air or on objects and surfaces.
The measles virus is present in the millions of tiny droplets that come out of the nose and mouth when someone with measles coughs or sneezes. A healthy individual who inhales these droplets can catch the infection.
The infection can also be spread if the droplets have settled on a surface and a healthy individual touches the surface and then places the contaminated hand over or near his or her nose and mouth.
Pathogenesis of measles
Once the measles virus enters the body, it multiples in the back of the throat and lungs and starts to spread throughout the body including the skin and respiratory system. The capability of infecting others lasts for two to four days before the rash appears and for about five days after it appears.
Risk factors for measles and its complications
Measles can affect all age groups of individuals. Anyone who has not had measles before and has not been vaccinated can be infected. Cases of re-infection are rare since the body builds immunity to the virus.
Those at a high risk are:
infants below 1 year
children between 1 and 5 years
people whose immune system is suppressed (those with HIV or after an organ transplant)
those with malnutrition
those (children) with vitamin A deficiency
Measles Diagnosis
Measles is most commonly diagnosed clinically based on signs and symptoms. There is a characteristic fever, rash and spots in the mouth that help in diagnosis of the condition.
Reporting measles
Measles is a notifiable disease. If a doctor makes the diagnosis of measles, he or she is obliged to report it to the local Health Protection Unit and in case of a child, to the child's school as well. This is done to prevent spread of the infection in the community.
Steps in the diagnosis of measles
Clinical symptoms including the characteristic rash and spots in the mouth are the primary step in diagnosing measles. In most cases this is enough to diagnose measles and isolate the affected person for at least 5 days after appearance of the rash to prevent spread of the infection to others.
Diagnosis that need to be ruled out – there are several conditions that may have similar features like measles. These need to be ruled out for confirmation of measles diagnosis. These include: –
Rubella or German measles – this is a milder form of measles and is similar in appearance.
Other viral infections like Parvovirus B19, Enterovirus infection, Human herpes virus type 7, Dengue fever etc.
Meningococcaemia or meningococcal infection
Kawasaki's disease
Human immunodeficiency virus (HIV) infection
Secondary syphilis
Drug eruptions or drug allergies
For a confirmed diagnosis a swab is used to take a sample of the saliva or a blood sample is taken. The serum and saliva are measured for measles-specific immunoglobulin M (IgM). This is positive in cases of measles for up to 6 weeks after onset of the disease. Urine samples may also yield the virus and the IgM. Serologic testing is most commonly by enzyme-linked immunoassay (ELISA or EIA). ELISA for IgM antibody requires only a single serum specimen and is diagnostic if positive.
After an infection the IgM shows an immediate rise that persists for a month or two. This is diagnostic of measles. There are, however, tests to detect measles specific IgG as well. The tests include ELISA, hemagglutination inhibition (HI), indirect fluorescent antibody tests, microneutralization, and plaque reduction neutralization. These are diagnostic only if a rise in the IgG can be showed. This is called the rise in titer of antibody against measles virus. Thus at least two samples of serum need to be collected. The first specimen should be drawn as soon after rash onset as possible. The second specimen should be drawn 10–30 days later. Both samples should have the same test at the same time. The specific criteria for documenting an increase in titer depend on the test.
Measles virus contains a single stranded RNA in its core. These RNA strands may be detected in saliva and other samples for confirmation of diagnosis.
Isolation of measles virus is not recommended as a routine method to diagnose measles. However, studies of these isolates help in molecular epidemiologic surveillance of measles and help in detecting the geographic origin of the virus and strains of the virus. The virus is more likely to be isolated when the specimens are collected within 3 days of rash onset.
Further tests include those with buccal scrapings. This includes gently scraping the cells of the inner linings of the cheeks. These cells are then placed over a slide and stained with special dyes called Leishman's stain. Under the microscope giant cells are visible.
Yet another method is to use special fluorescent dyes and with a process called immunofluorescence of a nasopharyngeal aspirate (NPA) the virus may be detected.