What is being tested?
Measles (rubeola) and mumps are members of the Paramyxoviridae family of viruses. They both cause illnesses in children throughout the world that are preventable through vaccination. Vaccination has drastically reduced the number of people affected by measles in Australia and in many parts of the world, but the World Health Organization (WHO) still lists measles as a leading cause of death in young children. According to their estimates, measles affects more than 20 million people a year and is responsible for close to 200,000 deaths, primarily in children under the age of five. These numbers take into account efforts that led to the vaccination of 576 million children in high risk countries from 2000 to 2007 and a corresponding decrease in the number of measles deaths by 74% during the same time period. Mumps, a milder illness, is not as widely vaccinated against and is still endemic in many parts of the world.
Data from the Australian Institute of Health and Welfare Mortality database show that in the 1930s around 1,000 deaths each year were caused by measles. By 2000 this had dropped to zero because of measles vaccination. However, in more recent years measles has staged a comeback due to less comprehensive vaccination coverage in Australia.
In 2011 in Europe, an outbreak of measles led to the reporting of 6,500 cases from 33 countries. Because of the risk of travellers, both visitors and returning Australians spreading measles, outbreaks such as this are a concern for health authorities in Australia.
Measles, also called rubeola, is an extremely contagious viral infection that is transmitted through respiratory secretions. The virus infects cells in the lungs and at the back of the throat and causes symptoms such as a high fever, dry cough, red eyes, light sensitivity, a runny nose, sore throat, tiny white spots inside the mouth, and a characteristic rash that typically starts on the face and spreads down the body to the trunk and legs. Most people recover within a couple of weeks, but up to 20 per cent develop complications that commonly include an ear infection, bronchitis, pneumonia or diarrhoea. Rarely (in 1 in a 1,000 infections) the brain is infected, often resulting in death or disability. People who are malnourished, have a vitamin A deficiency, or have compromised immune systems are frequently more severely affected. Women who are pregnant when they are infected with measles are at a greater risk of miscarriage or of premature labour.
Natural infection with measles rarely can cause a degenerative brain disease which can present many years after infection called subacute sclerosing panencephalitis. This condition progresses over 1-2 years and is always fatal. The overall mortality rate from measles in developed countries is approximately 2 in 1,000 persons.
Mumps is a viral infection that is transmitted through respiratory secretions or saliva. After a 2 to 3 week incubation period, an infected person typically develops flu-like symptoms such as a headache, muscle aches, and fever that are followed by characteristic parotitis – swelling of the salivary (parotid) glands below one or both ears. For most people, mumps is a mild, self-limited illness, but some may develop complications such as deafness, inflammation of the testicles (orchitis) or ovaries (oophoritis), pancreatitis, meningitis, or encephalitis.
Measles (rubeola) and mumps testing involves the detection of antibodies in the blood or, less commonly, the detection of the mumps or measles virus in a culture. Reverse-transcriptase polymerase chain reaction (RT-PCR) testing may be performed to confirm and investigate the source of measles infections. RT-PCR is faster and more sensitive than viral culture if performed on respiratory swab specimens. This testing is used to detect the measles virus and determine its genetic strain. The choice of test is dependent on the stage of illness in which the affected person is seen. For example, early in the infection, the test of choice may be detection of the virus by PCR while later in the infection, testing for antibodies provides the most reliable result.
How is it used?
Measles and mumps tests are primarily used to confirm that a person is immune to the viruses due to previous infections or vaccination. Doctors most frequently diagnose current measles and mumps infections based upon characteristic clinical findings. However there are several other illnesses causing rashes that can be confused with measles and people who are partially vaccinated or immunosuppressed may have an atypical presentation. Thus laboratory testing should be performed in possible measles cases.
Testing performed on suspected cases is used to confirm a diagnosis of an active or recent infection and may be required for public health purposes, especially if typical symptoms are not present. It may also be ordered along with other tests to distinguish between different causes of complications, such as an investigation of meningitis or swelling of the salivary glands found below and in front of the ear (parotitis) that may also be caused by bacterial infections.
Genetic testing (RT-PCR) is used to confirm suspected cases of measles and to investigate the source of the infection. This is done to tie cases together, in order to identify and address outbreaks, and to monitor the presence and movement of measles' genetic strains in Australia and worldwide.
There are several methods of detecting a measles or mumps infection:
Measles and mumps antibodies are virus-specific proteins produced by the immune system in response to an infection by the measles or mumps virus, or in response to vaccination. There are two types of antibodies produced, IgM and IgG. The first type to appear in the blood after exposure or vaccination is IgM antibodies. Levels of IgM antibodies increase for several days to a maximum concentration and then begin to taper off over the next few weeks. IgG antibodies take a bit longer to appear, but once they do, they stay in the bloodstream for life, providing protection against re-infection. If antibody testing is used it is important to collect two samples, one when the patient is acutely unwell and one later when they are recovering.
Viral detection involves finding the mumps or measles virus in a body fluid sample. This can be done either by detecting the virus's genetic material (RT-PCR) or less commonly by viral culture.
Viral genetic testing (RT-PCR) detects and identifies the genetic strain of the virus. This testing is most often ordered to confirm and evaluate suspected active cases of measles. Most RT-PCR testing is performed by public health laboratories.
Viral detection testing may occasionally be performed to identify the cause of severe complications that may be associated with an infection from the measles or mumps virus. Since people with weakened immune systems may not have a typical antibody response, a viral culture or a test to detect viral genetic material may be performed to confirm the diagnosis of a mumps or measles infection, especially if antibody results do not match clinical findings or a doctor's suspicions.
When is it requested?
Measles or mumps IgM and IgG antibody tests and/or acute and convalescent IgG antibody testing may be ordered when a person has characteristic signs and symptoms or when a doctor suspects that a person has a current or recent measles or mumps infection. An IgG antibody test for measles or mumps may be ordered whenever a doctor wants to determine whether a person is immune to one or both of the viruses, either because of a previous infection or due to vaccination.
A test to detect viral genetic material (RT-PCR) may be performed whenever a doctor wants to detect the virus and confirm a mumps or measles infection as the cause of a person's symptoms or complications and when an investigation of the source of the infection is warranted. These tests are typically ordered early in the course of the infection.
Signs and symptoms of measles develop 7-18 days after exposure and usually include one or more of the following:
Most people recover within a couple of weeks, but up to 20% develop complications that may include an ear infection, bronchitis, pneumonia, diarrhoea, encephalitis, or blindness.
Symptoms of mumps typically develop after a 2 to 3 week incubation period and often resemble symptoms of the flu such as:
Mumps is most often a mild self-limited illness, but some people may develop complications such as deafness, inflammation of the testicles (orchitis) or ovaries (oophoritis), pancreatitis, meningitis, or encephalitis.s
What does the result mean?
When measles IgM antibodies are present in someone who has not been recently vaccinated, then it is likely that the person has a current measles infection. However mumps IgM tests are unreliable due to the occurrence of false-positive mumps IgM results. When both IgM and IgG antibodies are present or there is a fourfold increase in concentrations between acute and convalescent IgG antibody tests, then it is likely that the person has a current or had a recent measles or mumps infection.
When measles or mumps IgG antibody is present in a person who has been vaccinated and/or is not currently ill, then that person is protected against infection (immune). If a person does not have measles or mumps IgG antibodies, then they are not considered immune to the viruses. This may be because they have not been exposed to the viruses, because the IgG has not had time to be produced, or because the person does not have a normal antibody response.
The following table summarizes results that may be seen with antibody testing:
|Positive||Positive (with increase in levels between acute and convalescent samples; this would only be done if the IgM test is not available)||Current or recent infection|
|Negative||Positive||Immunity from prior infection or vaccination|
|Negative||Negative||No current or prior infection; not immune; no or low immune response due to compromised immune system.|
If the measles or mumps virus is detected in a test for the virus's genetic material or viral culture, then the person has a current viral infection.
If a specific strain of measles or mumps virus is identified, then this genetic strain is both responsible for the infection and present at the tested person's location in Australia. This information can be used to help determine the source of a measles or mumps infection – such as recent travel to a specific country, or recent exposure to another person with an active infection. The result of measles or mumps genetic testing is used by public health authorities to monitor the movement of the virus and to identify outbreaks and prevent further spread.
If measles or mumps viruses are not identified in a viral detection test, it does not necessarily mean that the person does not have an active infection. The virus may have been present in numbers too low to detect or may not have been present in the sample tested.
Is there anything else I should know?
The measles, mumps, rubella (MMR) vaccine contains a live, attenuated (weakened) form of the viruses. Those with weakened immune systems and those who are pregnant or planning to become pregnant within the next month should not receive the vaccine. Recent vaccination can also cause positive results on both antibody testing and RT-PCR testing that may be difficult to distinguish from results caused by natural measles or mumps infection. Usually this can be clarified by further testing of the virus.
In most cases they will, but some complications, such as blindness, deafness, and rarely tissue or organ damage, may be permanent. The swelling of testicles (orchitis) that is sometimes seen with mumps can occasionally cause sterility.
Two doses of the MMR vaccine are needed for full protection. Children are given the first dose of MMR vaccine at 12 months of age and a booster immunisation is typically given at 4 years of age.
A test to document antibody response to the MMR vaccine is not recommended since most people mount an antibody response to the viruses in the vaccine. There are several common situations, such as entry to a university or employment in a health care setting, where you may need to provide proof that you have had the measles and mumps infections, or that you have had two MMR vaccinations, or that you have immunity to measles and mumps infection.
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