Dengue: magic water and the great social mobilization
Posted by apgaylard on May 2, 2009
Back in March I wrote about a study on the homeoapthic prophylaxis and treatment of dengue fever in Macaé (Rio de Janeiro, Brazil) It appeared in a re-branded open-access homeopathy journal grandly called the International Journal of High Dilution Research .
It really wasn’t very good and I sent some questions to its author. He has responded a number of times and seems to be a decent sort. He cleared up a number of reporting problems with the paper (I’ve put some explanatory notes in the original piece).
Some interesting things have come out of our dialogue. He confirmed what I had suspected: the 126 symptomatic individuals who were treated for dengue had not been allocated to this part of the trial at random. Neither had those who formed the ‘control’ group.
This is but one failing among many in this part of the study: no blinding, no placebo used in the control group, no measures of variance for the mean results or any tests of statistical significance. Not that the last point matters much; to quote Fisher, “The theory of estimation presupposes a process of random sampling. All our conclusions within that theory rest on this basis; without it our tests of significance would be worthless.”
Clearly, this part of the work is of no value. It should not have passed peer review; but that it did speaks eloquently about the quality of the peers.
The most interesting part of his reply concerned the attempted population-level prophylaxis. Its effectiveness was assessed by comparing the reported incidence of dengue in the area where it was deployed with other areas where it was not. Therefore it is absolutely critical that, as far as possible, the only difference between the dengue control strategy in these areas was that homeopathy was used in Macaé.
The paper explains that homeopathy was used alongside conventional control strategies. So I wondered whether the localities used as comparitors had benfitted from similar conventional support: was homeopathy the only difference?
The author replied that:
“The regions and municipalities perform the vector control, epidemiological surveillance and health education work in a manner similar to Macaé. The difference is the use of Homeopathy and the great social mobilization“
A “great social mobilization” sounded to me like a significant extra effort to control dengue in Macaé by non-homeopathic means. So I asked for clarification and the author kindly elaborated:
“In addition to the distribution of homeopathic medicine, intensive work was done for education in health for the population in the control of the vector, the symptoms of the disease, the flow of care […] and dissemination of dial-dengue, which is a telephone in which the user complains that may have local outbreak of mosquito, and is also for people with dengue notify us to take the measure of the vector control […] It also made the mapping of the areas with the highest rate of infestation of the larvae and greater number of cases of disease in these places and make joint efforts to identify and eliminate the outbreaks, guidance on the control of mosquitoes […] With all this, many people become aware of prevention methods in relation to dengue and seek health services as soon as symptoms begin, thus avoiding agravações [aggravated] disease”
These are a massively more plausible explanation for any real reduction in the number of cases of dengue than the application of drops of water containing (for all practical purposes) none of the intended ingredients. Or, as the author put it in the original paper:
“All three remedies were used in homeopathic dilution 30cH [1 part in 1060], due to the safety guaranteed by a dilution surpassing Avogadro’s number, making virtually insignificant the possibility of side-effects.”
Having clarified a number of issues with the author, I think that the journal is the best place to put the essentials into the public domain. So, here is a letter that I have just submitted for publication. It will be interesting to see if the journal is prepared to publish it.
Dengue: No Evidence Homoeopathy Works, No Reason Why It Should
I read with interest the recent paper by Nunes  and have the following observations.
A Flawed Trial
It is clear that no conclusions can be drawn from the reported treatment of 126 symptomatic patients. The author claims that, for these patients, “remission was earlier (average = 5 days), without complications, by comparison to patients who did not use homeopathy (average = 8.6 days)”.
It is notable that means are cited without any measure of variance (such as standard deviations or confidence limits) or statistical significance. In the absence of such data claims of actual differences in remission times cannot be sustained.
In addition, it seems that the trial did not blind either patients or clinicians to the treatment, or use an equivalent placebo in the control group. The allocation of patients to treatment or control groups was not randomised. These methodological flaws mean that the difference in remission times is most likely caused by a combination of bias and expectation effects.
Regression to the Mean
From the data provided in the paper (Figure 2) it is clear that dengue infection rates are cyclical, with an approximately five to six year period: peaks in one year are usually followed by dramatic falls the next year. This means that 2008 was likely to show a substantial fall in dengue infections, even in the absence of the homoeopathy campaign.
As the intervention in Macaé did not include a control group, it is important to ensure that comparisons with different areas or the same location for previous years are fair.
For instance, the author does not disclose whether the comparator regions operated a conventional public health campaign against dengue. If they did not, it is likely that any relative improvement Macaé is attributable to the conventional aspects of this campaign, rather than the novel homeopathic element, such as:
“[…] control of the vector, epidemiological surveillance and training of both health workers and the general population […] supportive and pharmacological management, as well as clinical follow up […]“
Neither does the author establish that comparator regions are of similar socio-economic make-up to Macaé.
It also seems peculiar to aggregate reported infections for January to March, when infections during 2007 peaked in April and May. This would appear to run the risk of missing the months with the greatest potential for dengue infection.
An Unremarkable Result
Commenting on the start of the homoeopathy campaign the author states, “From that moment on, a dramatic fall was recorded, not observed in the remaining localities”. And yet the data show that similar “dramatic falls” are not uncommon.
The main claim for control of dengue in the population of Macaé relates to the first three months of 2008. Totalling the data provided in Figure 1 for this period in other years reveals that three of the previous six years had fewer reported dengue cases during these months than the thirty-five claimed for 2008. (2004: 12; 2005: 5 and 2006: 10).
Looking at the data for complete years, Figure 1 reveals that there were only 31 and 17 reported cases of dengue in Macaé during 2004 and 2005, respectively. Also, between 2003 and 2004 dengue incidence fell by 93%. Finally, Figure 2 shows a similar decrease Litoral Sul Fluminense between 2006 and 2007.
From these data the reported dengue infection rates for early 2008 are certainly not without recent precedent.
I wholeheartedly agree with the author that, “confounding factors were not controlled for.” However, the methodological flaws identified preclude the conclusion that homoeopathy made any appreciable contribution to public health in this case. This view is strengthened by the paper not addressing itself to more likely alternative explanations, namely: bias, expectation effects, regression to the mean, inappropriate comparisons and natural variation in the incidence of dengue infections.
This view, rather than the author’s conclusions, is compatible with the outcome of the only RCT of homoeopathy for dengue currently listed in PubMed. A remedy containing Aconita, Bryonia, Eupatorium perforatum, Gelsemium, and Rhus toxicodendron was trialed in Honduras by Jacobs et al. . They concluded, “the results […] do not suggest that this combination homeopathic remedy is effective for the symptoms that are characteristic of dengue fever.”
In the absence of any credible supporting evidence for the efficacy of the homeopathic intervention reported, it is surprising that the author appears to see this work as some sort justification for the promotion of, “acupuncture, phytotherapy, […] and phytotherapic pharmacy.” None of these other alternative approaches were tested and phytotherapy directly contradicts many of the central tenets of homeopathy: similia similibus curentur and the ‘law of infinitesimals’, for example.
This paper provides no credible evidence that homoeopathy made any difference to dengue infections in Macaé during the first three months of 2008. The vanishingly small probability that any molecules of the ingredients were actually administered to anyone during this trial remains the best available explanation for this.
- Nunes LAS. Contribution of homeopathy to the control of an outbreak of dengue in Macaé, Rio de Janeiro. Int J High Dilution Res [online]. 2008 [cited 2009 Mar 08]; 7(25): 186-192. Available from: http://www.feg.unesp.br/~ojs/index.php/ijhdr/article/view/315/374
- Jacobs, J., Fernandez, E. A., Merizalde, B., Avila-Montes, G. A., and Crothers, D. The use of homeopathic combination remedy for dengue fever symptoms: a pilot RCT in Honduras. Homeopathy. 2007. 96: 22–26.
The author has told me that a double-blind randomized study is being planned at the moment. I look forward to seeing the results.
As for the putative prophylactic intervention in Macaé, maybe regression to the mean or natural variation in the incidence of the disease just made it look like it worked. However, I do think that there is a chance the campaign worked: it’s just that it wasn’t the magic water drops that did it.
If it did work, the author provides us with a much more sensible explanation: the vector control, education, awareness and surveillance elements of the “great social mobilization.” Now that’s a hypothesis worth testing.
Nunes LAS. Contribution of homeopathy to the control of an outbreak of dengue in Macaé, Rio de Janeiro. Int J High Dilution Res [online]. 2008 [cited 2009 May 02]; 7(25): 186-192. Available from: http://www.feg.unesp.br/~ojs/index.php/ijhdr/article/view/315/374
Fisher RA. Development of the theory of experimental design. Proceedings of the International Statistical Conferences. 1947 [cited 2009 May 02]; 3:434–39. Available from: http://digital.library.adelaide.edu.au/coll/special/fisher/212.pdf
Jacobs, J., Fernandez, E. A., Merizalde, B., Avila-Montes, G. A., and Crothers, D. The use of homeopathic combination remedy for dengue fever symptoms: a pilot RCT in Honduras. Homeopathy. 2007. 96: 22–26. doi:10.1016/j.homp.2006.10.004. PMID: 17227744.
I would like to thank Dr Laila Aparecida de Souza Nunes MD, BC (Homeopathy) – Municipal Coordinator of Collective Health, Municipal Secretary of Health, Macaé, Rio de Janeiro – for taking the time to reply to my questions and engage in an open, constructive discussion.
3rd May 2009. Typos and the odd spelling mistake corrected.
12 Responses to “Dengue: magic water and the great social mobilization”
Sorry, the comment form is closed at this time.