Measles and Mumps Tests

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.

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 requested 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 the UK. and worldwide. This type of testing may also be performed for the mumps virus.

There are several methods of detecting a measles or mumps infection:

Antibody testing
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 the IgM antibody. Levels of IgM antibodies increase for several days to a maximum concentration and then begin to fall 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.

Viral isolation (detection)
Viral isolation involves finding the mumps or measles virus in a body fluid sample. This can be done either by culturing the virus or by detecting the virus's genetic material (RT-PCR).

Viral genetic testing (RT-PCR) detects and identifies the genetic strain of the virus. This testing is most often requested to confirm and evaluate suspected active cases of measles or mumps. 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.

Measles or mumps IgM and IgG antibody tests and/or acute and convalescent IgG antibody testing may be requested 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 requested 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 viral culture or 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 requested 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:

• A characteristic rash that usually starts on the face and spreads down the body to the trunk and legs
• High fever
• Dry cough
• Red eyes
• Sensitivity to light
• A runny nose
• Sore throat
• Tiny white spots inside the mouth

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:

• Headache
• Muscle aches
• Fever
• These are followed by characteristic swelling of the salivary glands below one or both ears called parotitis.

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.

Antibody testing:
When measles or mumps IgM antibodies are present in someone who has not been recently vaccinated, then it is likely that the person has a current measles or mumps infection. 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. 

Viral isolation (detection):
If the measles or mumps virus is detected in a viral culture or test for the virus's genetic material, 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 the UK. 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 the CDC 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.

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.

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.