Just how many aHUS patients are there?

Rare Disease Day 2017 is over , the aHUS Global Video ( see here) was a tremendous success and, as has been said before ,the questions asked in it will be a great legacy of the day.
The alliance will now endeavor to get  answers to these questions over the coming months.

To start it  off  a question from Alaina of Norfolk Nebraska  who asks   ” How many people in the United States have aHUS and how many live in Nebraska, my home state?”
The true answer is no one knows. If records are kept in registries at local, country and global level no one is adding them all up and even if that was done there could be times when an aHUS patients feature in more than one registry.
In the largest of the aHUS Registries  – the Global aHUS Registry  there are only just under 1500 patient included so far  by Rare Disease Day 2017 , but within the next year or so that number could rise to 2000.
Furthermore many aHUS patients have not been diagnosed with the disease.
The number of patients with the disease at any particular time is  described as its prevalence. The prevalent number of patients can be added to as new incidents of the disease occur. The prevalence of aHUS grows by the incidence of new  aHUS patients and how many  aHUS patients survive.
The best approximation  of  aHUS patient numbers comes from studies of prevalence in different countries to provide a prevalence  %  of the population.
There is no agreement  on a what  level of aHUS prevalence %  to use, and estimates vary between 2 and 5.5 aHUS patients per million of population. ( i.e. 0.0001 and 0.00055 %)
So ,using the lower and upper estimates, within a world population  of nearly 7.5 billion there are between 15000 and 41000* surviving aHUS patients.
In the USA alone there would be between 650 and 1800 aHUS patients,
In Nebraska which has 1.9 million population so  there is  likely to be between 4 and 11 patients.
Choosing most likely figures somewhere in between the extremes would give 20,000 globally, 900 in USA and 5 in Nebraska.
Of whom 1 is Alaina.
So research is needed either to collate records accurately for existing or new patients;  or use the records to arrive at a more accurate universal prevalence statistic of “so many per million of the population”. Also research on barriers to diagnosis is needed to ensure all aHUS patients are identified, and quickly diagnosed.
In the mean time viewers can use the range 2 to 5.5 per million to research the number in their own country using the latest population figures.
While they are at  it an estimate of new cases each year in their country could also be made  using the range  to 0.4 to 1 per million
Which by next Rare Disease day will be  between  3000 to 7500 globally , 130 to 325 in the USA and 1 or 2 in Nebraska.
One thing is for sure very few of them will have known about aHUS when it happens.
* byway of comparison there are approximately 15 per million PNH patients or around 112000 worldwide.

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