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Elimination and the risk of malaria coming back afterwards

December 3, 2010 - 06:32 -- Bart G.J. Knols

This week a 31 year-old woman living in Jacksonville, Florida, got infected with the most deadly form of malaria, Plasmodium falciparum. Just weeks ago a similar report came from Spain, where indigenous transmission occurred and led to the first case of malaria since 1961.

Import cases of malaria are common in the USA (this year 111 travellers or returning immigrants returned to the USA with malaria) and estimates by the CDC are an average of 1300 import cases per annum.

Think of it. That's 1300 people arriving all over the USA, carrying malaria parasites that may infect local anophelines. And these anophelines may bite others that have no immunity whatsoever against malaria as the disease was eliminated from the USA some 59 years ago.

Yet, do we see malaria becoming endemic again in the USA? No. Do we see epidemic outbreaks anywhere on US soil? No.

That's interesting. I have attended numerous meetings and conferences in which the danger of returning malaria was often seen as (almost) a reason to not try and eliminate malaria anyway. Doom scenarios whereby an epidemic causes thousands of deaths were pictured there. And therefore loss of immunity remains a key issue in the elimination debate.

In the report 'Shrinking the malaria map' this is highlighted in a chapter titled 'Holding the line'. Examples are given of places (Mauritius, Kazakhstan, and South Korea) where elimination was followed by recurrence of the disease.

Two factors will determine the likelihood of malaria returning: the frequency at which parasites are brought in, and the intrinsic potential for transmission (local vectors, ecology, social environment etc.). Apparently, 1300 introductions in the USA and the presence of competent anophelines there are not enough to kick-start malaria again. 

But more is needed, and here is where the crux of the story lies: surveillance and a quick reaction force are key. A well functioning public health system is the key to keep malaria out once it is gone.

So the fear I heard at meetings was not so much the loss of immunity but merely the public health systems that would be insufficient to contain recurrence like that seen in Jacksonville this week. Is this an epidemiological issue? No. Is it a disease-related issue? No. Is it entomology? No. It is management.

The danger therefore lies in the loss of a region or country to sustain monitoring and surveillance and maintain the know-how and tools to contain a local outbreak. If this is not a problem in the USA, then why should it be a problem elsewhere?

Well, in many of the poorer nations the problem with elimination is the loss of interest to continue with doing just that: maintaining a proper surveillance system, competent personnel, and so on. The reason for this is simple: cash. Cash that is needed to deal with other, more pressing issues, when malaria is gone.

The lesson from all this is that shrinking the malaria map will come at a price, not just during the elimination effort itself, but beyond.

Cash and proper management. Something Florida does not have to worry about...


Jim Jackson's picture
Submitted by Jim Jackson on

Dear Bart,

Thank you for this important insight. I fully agree with the crux of this story. You state: "But more is needed, and here is where the crux of the story lies: surveillance and a quick reaction force are key".

But on the topic of this quick reaction force I have a question:
How would a quick reaction force be organised? How would it operate?
Who would be best equiped to do this and to manage this force?
It sounds rather military. Why?

Regards from a happy MalariaWorld user,


Bart G.J. Knols's picture
Submitted by Bart G.J. Knols on

@Jim - Any elimination effort not followed by proper and sustained surveillance should be discouraged. It is absolutely imperative to maintain vigilant for possible re-introductions of either pathogen or vector.

History tells us that maintaing such efforts under exisiting structures (for instance Ministries of Health) is hard to keep up at the required level and needed quality, so I would suggest outsourcing this to a commercial entity that is controlled through the government... as a suggestion...

Usa Lek-Uthai's picture
Submitted by Usa Lek-Uthai on

Dear Prof Dr Bart,
I strongly recognize that all factors you have mentioned are correlated to the malaria transmission elimination and/or eradication. The sustainable management is being an important approach to the malaria elimanation program. The endemic areas should have been predicted before the disease occur using GIS mapping, attributable data collection and entry, all related factors (environmental, entomological, epidemiological factors) and the database constructions. So we could do personnel protection from the malaria disease, whenever the rainfall, observe the mosquito density, observe the breeding sites characteristics, observe the entomological factors etc, then those factors will be entried to the simulation model program and analysed. The scoring or ranking would be the indicators for forecasting (??). The prevention programs then will be launched in those risk areas.ALL QUICK REACTIONS AND MAINTAINING ACTIVITIES are proper management of elimination!!!

share! hopefully malaria would be eliminated.

Usa Lek-Uthai,
Mahidol University,
Bangkok, Thailand