For many years, the Encephalitis Society had to simply estimate the incidence (occurrence, rate, or frequency of a disease) of encephalitis and we used to state around 4,000 cases a year in the UK (writes Dr Ava Easton the Chief Executive of the Encephalitis Society).

In 2013, however, a paper was published by Granerod¹ and colleagues following extensive work with Public Health England which gave us the first data for England, with capture/recapture models suggesting a best estimate for encephalitis incidence of 5.23 cases/100,000/year, although the models indicated that the incidence could be as high as 8.66 cases/100,000/year.

Given that the authors were also at pains to point out that this was likely an underestimate, and extrapolating figures to apply to the UK, this meant 6,000 cases a year in the UK. That’s a surprising 16 people every day. Other studies in Europe have reported incidences of up to 12.6 per 100,000.² Recent research conducted in the US suggests an average annual encephalitis-associated hospitalisation rate of 6.9/100,000 population.³

Dr Ava Easton

Understanding incidence on a global scale is more problematic. Global incidence figures are difficult to establish due to variations, such as the geographic distribution of factors that cause encephalitis; viruses and the vectors that transmit them; new and emerging vectors and viruses, or those which currently remain unknown to us; global warming and increasing industrial development of communities in rural areas; immunisation policies of different countries (i.e. some countries will have more or less encephalitis depending on whether they have vaccination programmes); and methodological issues such as how cases are defined, diagnosed and recorded.

In some countries, the majority of the victims are children. Probably the best paper to attempt to outline what this was by Jmor⁴ and colleagues in 2008 which suggested an incidence of around half a million people a year worldwide, that’s one person every minute. Again, this is likely to be an underestimate, and in my personal opinion I suspect it is a significant underestimate.

How many people are affected by the condition is important to us for one reason: the funding we need to address demand in terms of patients and families who need our help. Remember we are not just a UK organisation – the team here at Encephalitis HQ takes calls from around the world very day, and we remain the only organisation of our kind providing direct support, information, global awareness, and research.

It is also important to know how many people are affected so we can develop vaccines for causes of encephalitis such as has been done with Japanese encephalitis, rabies encephalitis, and tick-borne encephalitis.

Who is affected and by what cause has important implications for research – where should the focus for funding and research be? And of course, all this, without forgetting that we want to prevent (where we can) and treat successfully (where we cannot) ALL people affected by this devastating condition.

So, I was interested to read a new report recently which led me to realise that encephalitis is more common today, in many countries, than motor neurone disease (MND), cerebral palsy (CP), multiple sclerosis (MS) or bacterial meningitis. 

However, investment in medical research into encephalitis is meagre in comparison to these other conditions, and people affected by encephalitis don’t deserve to die unnecessarily or be left with life-changing disabilities.

Research into encephalitis is crucial and we are committed to increasing the amount of research we fund so that people affected by encephalitis can benefit from scientific advancements sooner.

But this cannot happen without money and the Encephalitis Society is the principal organisation involved in funding and collaborating on encephalitis research.

That’s why our Encephalitis Research Month is so important - to begin to accelerate our understanding as to why encephalitis happens, and to focus on new treatments and therapies, saving lives and bringing hope.

We need YOUR help – please can I call upon you to do two things today:

  1. Give up a pint of beer, a packet of cigarettes or a chocolate bar and make a donation, however small, to help us fund research.

I am always in awe of the amounts of money raised for causes like BBC Children in Need and Comic Relief – if we could replicate just 1% of what they raise we could make a real difference.

  1. Sign our petition when it goes live on our social media channels on 22nd June.

We will be asking you, via email and social media, to sign our petition highlighting the need for more funding into encephalitis research.

Thank you SO much for supporting Encephalitis Research Month – together we can save lives and make a real difference.



Bacterial meningitis

  • 2011/2012 around 3,300 cases of meningococcal disease and other bacterial forms of meningitis in the UK and Ireland (Meningitis Research Foundation Annual Report and Accounts 2011/2012).
  • 2014/2015 around 3,200 cases of meningococcal disease and other bacterial forms of meningitis in the UK and Ireland (In 2015, Men B and A, C, W, Y vaccines were introduced) (Meningitis Research Foundation Annual Report and Accounts 2014/2015).
  • Around 2,650 cases of bacterial meningitis and meningococcal septicaemia in the UK and Ireland (Meningitis Research Foundation, 2019-direct communication).
  • Incidence bacterial meningitis England 1.24/100,000 population (McGill F., M J Griffiths M.J., A Martin A.,et al. Incidence and healthcare costs of viral meningitis in adults - a multicentre prospective observational study in England. Lancet Infect Dis 2018; 18: 992–100).
  • Globally: 2,8 million people affected by meningitis (Meningitis Research Foundation website accessed 14/05/2019 )
  • Rates of meningococcal disease have been declining in the United States since the late 1990s. In 2016, there were about 370 total cases of meningococcal disease reported (CDC website accessed 14/05/2019,
  • Meningococcal meningitis is observed worldwide but the highest burden of the disease is in the meningitis belt of sub-Saharan Africa, stretching from Senegal in the west to Ethiopia in the east. Around 30 000 cases are still reported each year from that area (WHO website accessed 14/05/2019)

  • The incidence of bacterial meningitis in Western countries (Finland, Netherlands, and the United States) gradually declined by 3–4% per year to 0.7–0.9 per 100 000 per year in the past 10–20 years. In African countries (Burkina Faso and Malawi), incidence rates are still substantially higher at 10–40 per 100 000 persons per year. (Brouwer M.C., van de Beek D. Epidemiology of community-acquired bacterial meningitis. Curr Opin Infect Dis. 2018 Feb;31(1):78-84).
  • Australia: The incidence of meningococcal serogroup B (MenB) disease declined progressively from 1.52 cases per 100 000 population in 2001 to 0.47 per 100 000 in 2015. (Archer B.N., Chiu C.K., Jayasinghe S.H.,et al. 2017 Epidemiology of invasive meningococcal B disease in Australia, 1999–2015: priority populations for vaccination. Med J Aust; 207 (9): 382-387.
  • Latin America: The overall incidence of meningococcal disease per year varied from less than 0.1 cases per 100,000 inhabitants in countries like Mexico to two cases per 100,000 inhabitants in Brazil (Safadi, M.A.P., Gonzalez-Ayala S., Jakel A., et al. 2013The epidemiology of meningococcal disease in Latin America 1945–2010: an unpredictable and changing landscape. Epidemiol Infect. 2013 Mar; 141(3): 447–458)

Multiple Sclerosis (MS)

  • UK: Both MS incidence and prevalence rates have increased over the last few decades. The number of people with MS in the UK is growing by around 2.4% per year, due to people with MS living longer. 2013 Prevalence: 100,000 people live with MS in the UK. Incidence: 5,000 new cases every year (MS Trust website accessed 13/05/2019
  • USA: The incidence of MS increased from 34.8 per 100,000 in 2001 to 46.3 per 100,000 US populations in 2014 (Sharma K., Bittner F., Kamholz J., 2018, Epidemiology of multiple sclerosis in the United States Neurology. 2018 Apr 17;90(16):e1435-e1441.
  • Australia: Affects more than 23,000 people throughout Australia; 1,000 people diagnosed every year; The prevalence of MS in Australia in 2017 was 103.7 people with MS per 100,000, compared to 95.5 in 2010. This increase reflects global trends and likely reflects the increased survival of people with MS. (Multiple Sclerosis Australia, 2017 Federal Pre-Budget Submission )
  • Canada: The prevalence of MS increased by 69% from 1.57 (95% confidence interval [CI]: 1.54-1.59) per 1,000 in 1996 (n = 12,155) to 2.65 (95% CI: 2.62-2.68) in 2013 (n = 28,192). Incidence remained relatively stable except for a spike in 2010, followed by a subsequent decline in 2011-2013, particularly among young people and men. Incidence per 1,000 person-years was 0.158 in 1996 and 0.143  in 2009. In 2012 and 2013, incidence subsequently declined below baseline levels across all groups to a low of 0.099 per 1,000 person-years in 2013. Mortality decreased by 33% from 26.7 (95% CI: 23.5-30.3) per 1,000 to 18.0 (95% CI: 16.4-19.8) per 1,000. (Rotstein D.L., Chen H.,  Wilton A.S., et al. 2018 Temporal trends in multiple sclerosis prevalence and incidence in a large population. Neurology Apr 2018, 90 (16) e1435-e144)

Motor Neurone Disease/ALS

  • UK: 5 k people living in the UK an any one time (MND Association website accessed 13/05/2019 )
  • UK: incidence: 2/100,000; prevalence: 7/100,000; 4-5 years survival. (MNDA) (McDermott CJ, Shaw PJ, Diagnosis and management of motor neurone disease. BMJ. 2008 Mar 22336(7645):658-62).
  • A study 1990-2005 there was no increase in the incidence over time. (Alvaro Alonso, MD1, Giancarlo Logroscino, MD2, Susan S. Jick. Incidence and lifetime risk of motor neuron disease in the United Kingdom: a population-based study. Eur J Neurol. 2009 June ; 16(6): 745–751)
  • USA (amyotrophic lateral sclerosis -ALS): 5.0 cases per 100,000 persons in 2014, representing no increase from 2013. (CDC) (Mehta, P., Kaye, W., Raymond J., et al. Prevalence of Amyotrophic Lateral Sclerosis — United States, 2014, Weekly / February 23, 2018 / 67(7);216–218)
  • Europe: In Europe, the median (IQR) incidence rate (/100,000 population) was 2.08 (1.47–2.43), corresponding to an estimated 15,355 (10,852–17,938) cases. Median (IQR) prevalence (/100,000 population) was 5.40 (4.06–7.89), or 39,863 (29,971–58,244) prevalent cases (Chio A., Logroscino G., Traynor B.J., et al., 2013, Global Epidemiology of Amyotrophic Lateral Sclerosis: A Systematic Review of the Published Literature.  Neuroepidemiology 41(2):118-130).

Cerebral Palsy (CP)

  • 1 in 400 babies in the UK have a type of cerebral palsy. 1, 700 new cases in England and Wales (Cerebral Palsy UK website accessed 14/05/2019 )
  • Population-based studies from around the world report prevalence estimates of CP ranging from 1.5 to more than 4 per 1,000 live births or children of a defined age range (CDC website accessed 14/05/2019 ).



¹ Granerod, J., Cousens, S., Davies, N. W., Crowcroft, N. S. & Thomas, S. L. (2013) New estimates of incidence of encephalitis in England. Emerging Infectious Diseases 19: 1455–1462.

² Rantakallio, P., Leskinen, M. & von Wendt, L. (1996) Incidence and prognosis of central nervous system infections in a birth cohort of 12,000 children.  Scandinavian Journal of Infectious Diseases 18: 287-294.

³ Vora N.M., Holman R.C., Mehal J.M., et al. (2014) Burden of Encephalitis-Associated Hospitalizations in the United States, 1998- 2010. Neurology 82: 443–451.

⁴ Jmor, F., Emsley, H. C., Fischer, M., Solomon, T. & Lewthwaite, P. (2008) The incidence of acute encephalitis syndrome in Western industrialised and tropical countries. Virology Journal 5: 134.


⁶ Encephalitis incidence figures suggest the condition is generally more common than MND, CP, MS, and bacterial meningitis with a few exceptions. For example, MS in the US has a higher incidence, and bacterial meningitis has a higher incidence in sub-Saharan Africa, largely because in these countries the risk of catching meningitis is higher and they often have the least resources to respond effectively against the disease.

⁷ Also known as ALS or amyotrophic lateral sclerosis in North America.