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How to diagnose measles

Serologic testing for measles in low prevalence setting

Ongoing measles activity in other countries will result in sporadic cases of measles in the United States. Evaluation and interpretation of measles diagnostic results can be complex, particularly in measles elimination settings. Detection of specific IgM antibodies in a serum sample collected within the first few days of rash onset can provide presumptive evidence of a current or recent measles virus infection. However, because no assay is 100% specific, serologic testing of non-measles cases using any assay will occasionally produce false positive IgM results. Serologic tests can also result in false-negative results when serum specimens are collected too early with respect to rash onset.

In countries such as the United States where endemic circulation of measles has been eliminated, most suspected cases are not measles, and rash and fever illnesses are more likely due to a number of other rash–causing illnesses such as parvovirus B19, enteroviruses, or human herpesvirus–6 (roseola). The presence of rheumatoid factor (RF) can also result in a false positive IgM. Indirect EIA’s appear to be more affected by RF than IgM capture assays. Additionally, patients with throat or ear infections occasionally develop a rash following administration of antibiotics. Subsequent serologic specimens sent for measles IgM testing may result in a false positive test.

Laboratory evidence of immunity is based on testing to detect measles IgG. People who have negative or equivocal results for measles IgG should be vaccinated or revaccinated. In some cases vaccination is not possible, and testing with a second line diagnostic assay may be necessary to determine the patient’s immune status. CDC has evaluated the performance of several of the assays used to detect measles IgG (Latner et al, 2020). Some of the commercial, manually-processed enzyme immunoassays (ELISAs) are slightly more sensitive than high-throughput automated IgG test platforms that are typically used by large commercial laboratories. Contact CDC or the state public health laboratory for information on second line assays.

Instructions for blood collection (serum)

Blood for serologic testing of adults is collected by venipuncture. Collect 7–10 ml of blood in a red-top or serum-separator tube (SST). The preferred volume for IgM and IgG testing at CDC is 0.5–1 ml of serum to allow for re–testing; however, testing can be done with as little as 0.1 ml (100 µl) if necessary. Do not freeze tubes containing whole blood. Centrifuge blood collection tubes (10 min at 2200 – 2500 rpm) to separate serum from clot. Gel separation tubes should be centrifuged no later than 2 hours after collection. Aseptically transfer serum to a sterile tube that has an externally threaded cap with an o–ring seal. Store specimens at 4°C and ship on wet ice packs. Hemolyzed and lipemic serum and plasma are noted and tested, usually without apparent interferences.

Blood for serologic testing of infants or small children can be collected by finger/heel stick. Capillary tubes can be utilized for infants. Capillary tubes require the submitter to have access to a hematocrit centrifuge. Clinical laboratories should have 50 or 100 µl capillary tubes that are typically used for a variety of tests such as hematocrits or total lipids on newborns. At least 3 of the 50 µl hematocrit capillary tubes should be collected and spun in a hematocrit centrifuge.

Submission of samples to CDC for measles serologic testing: Q & A

What tests are available for laboratory confirmation of measles?

A capture IgM EIA (non-quantitative) that incorporates a recombinant measles nucleocapsid protein as the antigen is used to detect measles IgM. A commercial, indirect EIA (non-quantitative) assay is used for detection of IgG. Viral detection methods include standard methods of culturing virus in appropriate cell lines and techniques, such as real time RT-PCR to detect measles viral RNA. RT-PCR is available at many state public health laboratories and though the APHL/CDC Vaccine Preventable Disease Reference Centers external icon .

Who can send samples to CDC?

To determine where to send specimens for testing please contact your health department. Specimens can be shipped to the state laboratory, the VPD-RC, or CDC. See the Specimen Collection, Storage and Shipment page.

Does CDC provide testing for any suspected case of measles?

During outbreaks of measles, the CDC measles laboratory can assist with testing.

To expedite confirmation of measles from highly suspicious cases (recent travel, classic measles signs and symptoms), particularly in a setting with many potential exposures, an aliquot of serum, and a nasopharyngeal swab can be sent to CDC while testing is underway at the SPHL or local clinical laboratory.

Requests for measles serologic testing that are strictly for rule–out purposes (low index of suspicion, does not meet clinical case definition, no travel or contact with cases), should be directed to either SPHLs or clinical laboratories. Prior communication with CDC’s Viral Vaccine-Preventable Diseases Branch (VVPDB) regarding suspected cases of measles that require assistance is preferred.

What information is needed with the specimen and when will the result be available?

A completed 50.34 submission form must be submitted with each specimen. It is important to include the date of measles vaccinations, if applicable, and the dates of rash onset and blood collection. A patient identification number and/or name as well as the patient date of birth should be entered on the form.

Serum specimens for measles serologic testing (IgG, IgM) are delivered by courier to the STAT (Specimen Triage and Tracking) laboratory at CDC. Samples are then delivered to the VVPDB measles lab (Unit #81). The turnaround–time for testing samples for IgM and IgG is 7 working days after the delivery of samples to the measles reference lab by the STAT lab.

When situations require immediate notification of a result, please inform the laboratory (Paul Rota 404-639-4181 or Carole Hickman 404-639-3339) upon submission of the sample. Provide a telephone number, email address, and fax number.

Specialized serologic testing available at CDC: avidity and PRN assays

IgG avidity testing and a plaque reduction neutralization (PRN) assay are available when case classification requires additional methods to confirm measles infection, usually when the result obtained for IgM is suspected of being a false negative or a false positive (Sowers et al). These assays may be offered when confirmation by RT-PCR was not successful or a molecular sample was not available. Prior approval from the VVPDB laboratory (Carole Hickman 404-639-3339) should be obtained. Avidity testing and the PRN assay require specialized reagents and their use is limited to unusual cases, typically in an outbreak setting, when cases with mild or a non-classic presentation of measles are detected.

A single serum can be tested for IgG avidity; however, samples must have detectable IgG. Both an acute and a convalescent phase serum are recommended for PRN testing.

How do you diagnose measles diagnosis? Your doctor should be able to diagnose measles from the combination of symptoms you may have, such as the characteristic rash and the small spots inside the mouth. They might do a swab test from the back of the nose and order a blood test or urine test to confirm measles.

How is measles diagnosed in a lab? IgM serology is the mainstay of measles laboratory diagnosis. Direct detection of measles virus by nucleic acid test (NAT), immunofluorescence or viral culture may aid diagnosis when persisting IgM from vaccination is a possibility.

What tests are done to diagnose measles? If necessary, a blood test can confirm whether the rash is truly measles. The measles virus can also be confirmed with a test that generally uses a throat swab or urine sample.

Can a blood test detect measles? Detection of specific IgM antibodies in a serum sample collected within the first few days of rash onset can provide presumptive evidence of a current or recent measles virus infection.

How do you diagnose measles diagnosis? – Related Questions

How long does a blood test take for measles?

Test Frequency and Turnaround Time (TAT)

Measles serology to detect Measles IgG and IgM is performed daily Monday to Friday. Turnaround time for test results is up to 5 days from receipt by PHO laboratory.

What can be mistaken for measles?

Rubeola (measles) is often confused with roseola and rubella (German measles), but these three conditions are different. Measles produces a splotchy reddish rash that spreads from head to foot. Roseola is a condition that affects infants and toddlers.

How do you rule out measles?

Detection of measles-specific IgM antibody in serum and measles RNA by real-time polymerase chain reaction (RT-PCR) in a respiratory specimen are the most common methods for confirming measles infection.

Is bathing allowed in measles?

Sponge baths with lukewarm water may reduce discomfort due to fever. Drink plenty of fluids to help avoid dehydration. A humidifier or vaporizer may ease the cough and nasal congestion.

What should you not do when you have measles?

If you’re sick with measles: Stay home from work or school and other public places until you aren’t contagious. This is four days after you first develop the measles rash. Avoid contact with people who may be vulnerable to infection, such as infants too young to be vaccinated and immunocompromised people.

How long does it take to confirm measles?

Measles signs and symptoms appear around 10 to 14 days after exposure to the virus. Signs and symptoms of measles typically include: Fever. Dry cough.

Are there 2 types of measles?

Types of measles

Standard measles, sometimes known as red measles, or hard measles, is caused by the rubeola virus. German measles, also known as rubella, is an entirely separate illness caused by the rubella virus and is usually a milder infection than standard measles.

Where does the measles rash start?

It usually begins as flat red spots that appear on the face at the hairline and spread downward to the neck, trunk, arms, legs, and feet. Small raised bumps may also appear on top of the flat red spots. The spots may become joined together as they spread from the head to the rest of the body.

What causes Measle?

Measles is caused by morbillivirus, which is mostly seen in the winter and spring. It’s spread from one child to another through direct contact with discharge from the nose and throat. Sometimes, it is spread through airborne droplets (from a cough or sneeze) from an infected child.

Does the measles rash itch?

These are called Koplik’s spots and are unique to measles. Days 3 to 5: after 3 to 5 days a blotchy, flat red rash appears. It usually starts behind the ears and then spreads to the face, body and then the arms and legs. The rash may or may not be itchy.

What diseases look like measles?

Both roseola and measles may look similar in appearance as they usually present with a maculopapular rash. However, roseola rash is usually more pink-red, while measles rash is more red-brown. While it may be easy to confuse the two, other features help to differentiate between roseola and measles.

How long can measles last?

How Long Does Measles Last? A measles infection can last for several weeks. Symptoms usually start 7–14 days after someone is exposed to the virus.

What should I do if I suspect measles?

You should contact a GP as soon as possible if you suspect that you or your child may have measles. It’s best to phone before your visit as your GP surgery may need to make arrangements to reduce the risk of spreading the infection to others.

Does measles go away on its own?

There’s no specific treatment for measles, but the condition usually improves within 7 to 10 days. A GP will probably suggest taking things easy at home until you’re feeling better. Stay away from work or school for at least 4 days from when the measles rash first appears to reduce the risk of spreading the infection.

How long can measles last in the air?

Measles is one of the most contagious diseases

Infected people can spread measles to others from four days before through four days after the rash appears. Measles virus can live for up to two hours in an airspace after an infected person leaves an area.

Which antibiotic is best for measles?

In 1987 it was decided that all children younger than 3 years of age seen within the first 2 weeks of the onset of measles symptoms should be treated with the antibiotic trimethoprim-sulfamethoxazole for 7 days irrespective of whether they had signs of bacterial infection at the time of clinical examinations.

Can you get measles if you are vaccinated?

Measles is rare in Australia – your child has a low chance of contracting the virus if they have been immunised.

What are hard measles?

Hard measles: An acute highly contagious viral disease with fever, runny nose, cough, red eyes, and a spreading skin rash. The eight-day measles is the ordinary measles, also known as rubeola, a potentially disastrous disease.

How can you tell the difference between measles and rubella?

Measles is more severe than rubella, and highly contagious. Though both measles and rubella have similar symptoms such as rash, the fever between the two is slightly different. Rash, and symptoms of measles last longer than rubella. Though measles does, Rubella has no prodromal period.

Can you get measles at any age?

Measles can be contracted at any age. Infants and children are often believed to be the only age groups affected by measles, but the disease also spreads among teenagers and adults, so check your vaccination status.

What are the pathognomonic signs of measles?

It can affect people of all ages, despite being considered primarily a childhood illness. Measles is marked by prodromal fever, cough, coryza, conjunctivitis, and pathognomonic enanthem (ie, Koplik spots), followed by an erythematous maculopapular rash on the third to seventh day.

How to diagnose measles

  • Measles (Rubeola)
  • How is measles spread and what are the symptoms?
  • Diagnosis and treatment of measles
  • What are the complications and risks of measles?
  • The measles vaccine
  • You may have a few more questions about measles

How is measles diagnosed?

Should you feel as though you may have been infected or are showing signs of measles, it is best to immediately seek the opinion of a medical professional.

Measles is typically diagnosed when your doctor examines your skin rash, checks for signs of Koplik’s spots in your mouth (little white spots on your cheeks), and also checks for a hacking cough, sore throat and fever. If your symptoms are unable to give a clear diagnosis, your doctor may also conduct a blood test (obtain a small blood sample to send to the lab for testing) in order to confirm the diagnosis.

The diagnosis can also be confirmed by testing a throat swab (viral culture) or urine test, known as a PCR ( Polymerase Chain Reaction ). Measles is a notifiable disease, therefore, it is preferred if the diagnosis is confirmed with testing.

Sometimes your rash may be the result of something else and can be difficult to diagnose, regardless, you should always seek a diagnosis from your doctor.

How do you treat measles?

There is no specific treatment for measles, however, there are certain precautions and measures that are able to be taken by those who are more vulnerable (weak immune system) or have had exposure to the virus:

  • People who have not been vaccinated, as well as children, can be vaccinated within the first 72 hours after exposure. If the infection still develops, it often results in much milder symptoms than if the patient had not been vaccinated. This is known as post-exposure vaccination.
  • Infants, pregnant women and those with a weak immune system, who have been exposed to measles, may be able to get an injection known as immune serum globulin, which contains antibodies (proteins). This is administered within six days after initial exposure and may prevent measles being contracted or lessen the symptoms.

If the measles virus has been contracted, there are a variety of medications that your doctor may prescribe, these include:

  • Antibiotics are used if a secondary bacterial infection has been contracted after being infected with measles, such as ear infection or pneumonia. Measles, being a virus, cannot be treated by antibiotics as these will have no effect on the infection.
  • As discussed earlier, people with a vitamin A deficiency may be at higher risk for contracting measles or their symptoms may be worsened. Your doctor may prescribe a dose of 200,000 UI ( international units) taken over two days.
  • Over-the-counter fever reducers are also available, such as ibuprofen and acetaminophen. However, speak to your pharmacist about these as caution must be taken when giving aspirin to your child or teenager who has a viral infection.

There are also a number of home-remedy solutions. These should only be carried out once your doctor has diagnosed you or your child with measles, and it is important to keep in touch with your doctor regarding your symptoms and progress. These include:

  • Getting plenty of rest and avoiding physical activities that may exhaust you.
  • Staying hydrated and drinking plenty of fluids to replace fluids lost through sweating and fever. These include water and fruit juice – you should be drinking six to eight glasses of water a day.
  • Using a humidifier in your room to help you to breathe easily and soothe your sore throat and cough.
  • Trying to rest your eyes and avoid bright light as it may be bothersome. Avoid watching too much television and wear sunglasses when exposed to sunlight.