Measles, resulting from measles virus (MeV) infection can cause immune suppression and “immune amnesia”. MeV infection most often affects non-immune children but can occur in any age group. Immune suppression and immune amnesia are overlooked outcomes of MeV infection. Key cells that remember past infections and produce responses to prevent disease if you get infected again are drastically reduced in number. There’s a lot of measles in the Democratic Republic of the Congo (DRC) right now. Know what else there is there? Ebola virus. In kids. Could measles virus and Ebola virus be working together in the DRC?

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While the ongoing Ebola virus disease (EVD) outbreak in the DRC attracts most of the infectious disease media attention, there is also a huge surge in easily transmitted MeV infections happening at the same time, in the same region of the DRC.[1] To confuse matters, some of the signs and symptoms of EVD – fever, redness around the eyes, diarrhoea – are virtually indistinguishable from those experienced when suffering measles, malaria or cholera.[2,5]

Even more alarming is that there have been more deaths attributed to MeV (2,758 from Jan to late Aug 2019) in the DRC, than to EVD (2,052 reported since Jul 20918) in 2019.[3]

The young have been hit harder by EVD

A particularly unwanted feature of the unwanted 2018-19 DRC EVD outbreak has been the high number of children diagnosed compared to previous EVD outbreaks.[4,7,9,10,13]

Of 1,994 deaths to 26th of August this year, 801 (40%) have been children.[6] Children also bear the brunt of disease and death due to MeV infection.[8]

The impact of EVD in children during the ongoing outbreak is unprecedented so what might be different about this outbreak compared to the previous ones? Some things to consider include:

• are infections occurring when children are inadvertently exposed to the Ebola virus during visits to clinics for other infections such as measles or malaria?[13,15]
• is infection control among traditional healers, hospitals and health centres worse now than in past outbreaks?
• are there more infections via breastfeeding – an area that is in desperate need of more research [11]?
• could there be less shielding of children from their infected family members than in previous outbreaks?
• is nutrition – and its impact on a healthy immune response – an issue here when it hasn’t been previously?
• are children somehow being even more affected by dehydration due to vomiting, diarrhoea and blood loss than is usual for EVD? [12]
• are children being better identified in this outbreak?
• are more deaths among children due to carers waiting longer because of what initially looks like a “normal” childhood infection before presenting for the specialized medical care needed for paediatric EVD cases?[14]
• are children being made to work in outbreak-related roles more than has been usual in the past?

MeV infection does more than produce measles

It’s been known for over 100 years that MeV infection is immunosuppressive [16,17]; it silences the effective immune response to other infections. Measles also reduces immune memory for 2 to 3 years and can result in increased deaths over this period compared to MeV-immune people.[20]

The mechanism for suppression and amnesia revolves around which cells MeV infects and destroys.[20] You guessed it. It kills off the immune memory blood cells that hold the ability to rapidly respond – with antibodies and killer and control immune cells – to the return of a multitude of viral and bacterial nemeses from days gone past.

These memory B cells and memory T cells are a precious asset to our ongoing health.

After recovery from MeV infection, cell numbers return to normal levels, but we now lack the strength and spectrum of our immune memory. Ironically for MeV, measles doesn’t stop us mounting a good immune response to it. Measles resets the clock and restocks our immune pantry with anti-MeV responses but not with much else.

We’ve now forgotten our infectious enemies.

Why don’t we hear more about this?

Despite measles immune suppression being known about for decades, we don’t hear a lot about it. Which is really strange. Especially in these times of worldwide measles-palooza. It seems like an obvious thing to use when discussing vaccine benefits with those unsure about vaccines.

The measles vaccine effectively protects us from measles without suppressing our immune memory or giving us immune amnesia. Not only does a measles vaccine dramatically reduce the risk of serious outcomes like encephalitis and death, but this safe vaccine also lets us keep all our happy immune memories intact.

How does measles make us forget previous infections?

MeV uses CD150, a molecule found on the surface of some of our immune cells, as a receptor. MeV can infect these cells and hitch a ride to travel all over our body. It also kills these cells.

Turns out that our immune memory cells have more of these receptor molecules than do the cells that have yet to develop a memory.

A case study of MeV on an island

In 1911, there was a well-observed introduction of MeV to an isolated, immunologically naive population. More than half of the children in the 1910 and 1911 birth-year cohorts of the Fijian island of Rotuma, died during their first two years of life after MeV exposure.[19]

Overall, 13% of the population died due to causes attributed to measles.

Measles-related deaths occurred at a higher rate among Rotuman women in 1911. Interestingly, women have also been over-represented among fatal EVD cases during the latest outbreak in the DRC. Gastrointestinal complications were the main feature among fatal cases on Rotuma. Tuberculosis-related death rates were also higher among those studied in 1911 than among the same group in any of the following 50 years. The impact of MeV extends well beyond just measles.

Could Measles virus and Ebola virus be working together in the DRC?

As it did on Rotuma with tuberculosis and has done elsewhere for other diseases, could MeV be paving the way for a follow-up disease – this time EVD – to occur more often and more severely, among children and women in the DRC?

I don’t have the answer and I haven’t seen any data that rule it out or in but this seems like a question that should be asked and investigated if it hasn’t already been.

This entire MeV story is yet another reason why vaccination programs are such an essential part of a healthy population. The measles outbreaks we are seeing in countries all over the world – apart from being worrying and expensive to contain – indicate that immunity has lapsed in pockets and is absent in entire countries.

Getting measles from MeV infection is only the first step on a path to poor health in the ensuing years. #Vaccineswork in more than just the most obvious ways.

References

1. Measles vaccination begins in Ebola-hit Congo amid fears of ‘massive loss of life’
   https://www.theguardian.com/global-development/2019/jul/12/measles-vaccination-begins-in-ebola-hit-congo-amid-fears-of-massive-loss-of-life
2. Mass measles vaccination campaign begins in Ebola-hit DR Congo province
   https://news.un.org/en/story/2019/07/1042221
3. Measles has killed more people in DR Congo this year than Ebola epidemic, MSF says
   https://www.france24.com/en/20190817-drcongo-measles-killed-more-ebola-epidemic-msf-vaccine
4. https://www.bignewsnetwork.com/news/262262737/one-in-five-ebola-fatalities-in-past-year-have-been-children
5. https://www.unicef.org/emergencies/ebola
6. https://www.unicef.org/drcongo/en/what-we-do/emergency-response/ebola-outbreak
7. https://www.unicef.org.uk/press-releases/protecting-children-and-engaging-communities-key-to-ending-ebola-outbreak-in-the-democratic-republic-of-the-congo-as-deaths-pass-2000/
8. https://www.who.int/news-room/fact-sheets/detail/measles
9. https://www.pbs.org/newshour/health/an-ebola-outbreak-presents-a-new-mystery-involving-children
10. https://www.savethechildren.org/us/about-us/media-and-news/2019-press-releases/ebola-spike-in-democratic-republic-of-congo
11. Ebola virus disease and breastfeeding: time for attention
    https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(19)32005-7/fulltext
12. https://www.aap.org/en-us/advocacy-and-policy/aap-health-initiatives/Children-and-Disasters/Pages/ebola_faqs.aspx
13. An Ebola outbreak presents a new mystery involving children
    https://www.statnews.com/2018/10/19/ebola-outbreak-new-mystery-children/
14. https://www.voanews.com/africa/children-hardest-hit-ebola-epidemic-dr-congo
15. Ebola detectives race to identify hidden sources of infection as outbreak spreads
    https://www.nature.com/articles/d41586-018-07618-0
16. Natural measles causes prolonged suppression of interleukin-12 production
    https://www.ncbi.nlm.nih.gov/pubmed/11398102
17. Measles Virus-Mononuclear Cell Interactions.
    https://www.ncbi.nlm.nih.gov/pubmed/7789164
18. https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-83-6-1431#tab2
19. Extreme Mortality After First Introduction of Measles Virus to the Polynesian Island of Rotuma, 1911
    https://academic.oup.com/aje/article/173/10/1211/184695
20. Long-term measles-induced immunomodulation increases overall childhood infectious disease mortality
    https://science.sciencemag.org/content/348/6235/694

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