Tag Archives: Infectious disease

Is Disease Eradication Always the Best Path?

Originally published at PLoS Speaking of Medicine

There is no question that the eradication of smallpox, a devastating illness costing millions of lives, was one of the greatest achievements of 20th-century medicine. The disease was triumphantly declared eradicated by the World Health Assembly in 1980. Smallpox eradication required extremely focused surveillance as well as the use of a strategy called “ring vaccination,” in which anyone who could have been exposed to a smallpox patient was vaccinated immediately. Why was smallpox eradication possible? For one thing, smallpox is easily and quickly recognized because of the hallmark rash associated with the illness. Second, smallpox can be transmitted only by humans. The lack of an animal reservoir makes controlling the illness much simpler.

The success of smallpox eradication campaigns has resulted in persistent calls to eradicate other infectious diseases in the years since 1980. Unfortunately, disease eradication can be difficult and even impossible in the case of many infectious diseases, and it is crucial to consider the features of each illness in order to come to a proper conclusion about whether the pursuit of disease eradication is the best approach. In the first place, it is important to be clear about what “eradication” means. Eradication refers to deliberate efforts to reduce worldwide incidence of an infectious disease to zero. It is not the same as extinction, the complete destruction of all disease pathogens or vectors that transmit the disease. Elimination, a third concept, encapsulates the complete lack of a disease in a certain population at a certain point in time. Disease eradication therefore specifies a particular strategy for dealing with infectious diseases; other options exist that in some circumstances may be more desirable.

Can the pursuit of disease eradication ever be detrimental? It could be in the case of certain diseases that do not lend themselves easily to total eradication. A claim of eradication logically ends prophylactic efforts, reduces efforts to train health workers to recognize and treat the eradicated disease, and halts research on the disease and its causes. When eradication campaigns show some measure of success, financial support for the control of that illness plummets dramatically. Wide dissemination of information about eradication efforts without the certification of success can therefore prove detrimental. In these cases, complacency may prematurely replace much needed vigilance. If there is a reasonable chance of recurrence of the disease or if lifelong immunity against the disease is impossible, then attempting eradication may prove disastrous because infrastructure to control the disease would be lacking in the event of resurgence. Tracking down the remaining cases of an illness on the brink of eradication can be incredibly costly and divert government money in resource-poor nations from more pressing needs.

Another potential problem with disease eradication efforts is that, as a vertical approach, they may drain resources from horizontal approaches, such as capacity building and health system strengthening. Some advocate a more “diagonal” approach that uses disease-specific interventions to drive improvements of the overall health system. Still others have argued that vertical approaches that treat one disease at a time may divert resources from primary healthcare and foster imbalances in local healthcare services. Vertical schemes may also produce disproportional dependence on international NGO’s that can result in the weakening of local healthcare systems.

Malaria offers an excellent example of a case in which debate rages about whether eradication efforts would be successful. There are four species of single-cell parasite that cause malaria, the most common of which are P. falciparum and P. vivax. P. falciparum is the most deadly and P. vivax is the most prevalent. These two species make it difficult to engineer a single, fool-proof vaccine. Further complicating developing a vaccine for malaria are the ability of the parasites to mutate so that even contracting malaria does not confer life-long immunity. Furthermore, malaria involves an animal vector (mosquitoes). It would clearly be a huge challenge and perhaps even impossible to wipe out malaria completely. Beginning in 1955, there was a global attempt to eradicate malaria after it was realized that spraying houses with DDT was a cheap and effective way of killing mosquitoes. The initiative was successful in eliminating malaria in nations with temperate climates and seasonal malaria transmission. Yet some nations, such as India and Sri Lanka, had sharp reductions in malaria cases only to see sharp increases when efforts inevitably ceased. The state of affairs in India and Sri Lanka demonstrates some of the negative effects of eradication campaigns that are not carried to fruition. The project was abandoned in the face of widespread drug resistance, resistance to available insecticides, and unsustainable funding from donor countries. This failure was detrimental because the abandoned vector control efforts led to the emergence of severe, resistant strains that were much harder to treat.

Recently, discussions of malaria eradication have begun again. At the moment, there is considerable political will and funding for malaria eradication efforts from agencies such as the Gates Foundation. The Malaria Eradication Research Agenda Initiative, in part funded by the Gates Foundation, has resulted in substantial progress in identifying what needs to be done to achieve eradication. Even so, proponents of malaria eradication admit that this goal would take at least 40 years to achieve. It is not clear how long current political will and funding will last. There are concerns that political will might wither in the face of the estimated $5 billion annual cost to sustain eradication efforts.

Disease eradication can clearly be an incredibly important public health triumph, as seen in the case of smallpox. But when should the strategy be employed and when is it best to avoid risks associated with eradication efforts that might fail? Numerous scientific, social, and economic factors surrounding the disease in question must be taken into consideration. Can the microbe associated with the disease persist and multiply in nonhuman species? Does natural disease or immunization confer lifelong immunity or could reinfection potentially occur? Is surveillance of the disease relatively straightforward or do long incubation periods and latent infection make it difficult to detect every last case of the illness? Are interventions associated with eradication of the disease, including quarantine, acceptable to communities globally? Does the net benefit of eradication outweigh the costs of eradication efforts? Proposals for disease eradication must be carefully weighed against potential risk. Rather than being presented as visionary, idealistic goals, disease eradication programs must be clearly situated in the context of the biological and economic aspects of the specific disease and the challenges it presents.

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The infelicities of quarantine

Originally published at PLoS Speaking of Medicine

In 2009, as panic struck global health systems confronted with the H1N1 flu epidemic, a familiar strategy was immediately invoked by health officials worldwide: quarantine. In Hong Kong, 300 hotel guests were quarantined in their hotel for at least a week after one guest came down with H1N1. Such measures are certainly extreme, but they do raise important questions about quarantine. How do we regulate quarantine in practice? How do we prevent this public health measure from squashing civil liberties?

Quarantine as a method of containing infectious disease might be as old as the ancient Greeks, who implemented strategies to “avoid the contagious.” Our oldest and most concrete evidence of quarantine comes from Venice circa 1374. Fearing the plague, a forty-day quarantine for ships entering the city was enacted, during which passengers had to remain at the port and could not enter the city. In 1893, the United States enacted the National Quarantine Act, which created a national system of quarantine and permitted state-run regulations, including routine inspection of immigrant ships and cargoes.

“Quarantine” must be differentiated from “isolation.” While isolation refers to the separation of people infected with a particular contagious disease, “quarantine” is the separation of people who have been exposed to a certain illness but are not yet infected. Quarantine is particularly important in cases in which a disease can be transmitted even before the individual shows signs of illness. Although quarantine’s origins are ancient, it is still a widely used intervention. For example, the U.S. is authorized to quarantine individuals with exposure to the following infectious diseases: cholera, diphtheria, infectious tuberculosis, plague, smallpox, yellow fever, viral hemorrhagic fevers, SARS, and flu. Federal authorities may quarantine individuals at U.S. ports of entry.

The history of quarantine is intimately intertwined with xenophobia. There is no question that quarantine has been frequently abused, serving as a proxy for discrimination against minorities. This was especially true in late nineteenth- and early twentieth-century America, coinciding with large numbers of new immigrants entering the country. A perfect example of the enmeshed history of quarantine abuse and xenophobia occurred in 1900 in San Francisco. After an autopsy of a deceased Chinese man found bacteria suspected to cause bubonic plague, the city of San Francisco restricted all Chinese residents from traveling outside of the city without evidence that they had been vaccinated against the plague. In 1894, confronted with a smallpox epidemic, Milwaukee forcibly quarantined immigrants and poor residents of the city in a local hospital. In these cases, quarantine served as a method of containing and controlling ethnic minorities and immigrants whose surging presence in the U.S. was mistrusted.

A more recent example stems from the beginning of the AIDS epidemic in the early 1980s. In 1986, Cuba began universal HIV testing. Quarantines were instituted for all people testing positive for HIV infection. In 1985, officials in the state of Texas contemplated adding AIDS to the list of quarantinable diseases. These strategies were considered in a state of panic and uncertainty about the mode of transmission of HIV/AIDS. In retrospect, we know that instituting quarantine for HIV would have been not only ineffective but also a severe violation of individual liberties. Early in the AIDS epidemic, some individuals even called for the mass quarantine of gay men, indicating how quarantine could be used as a weapon against certain groups, such as immigrants and homosexuals. Because of their extreme nature and their recourse to arguments about protecting public safety, quarantine laws are especially prone to abuse of the sort witnessed in these cases.

How can we prevent quarantine laws from being abused? For one thing, these laws must be as specific as possible. How long can someone be quarantined before being permitted to appeal to the justice system? In what kinds of facilities should quarantined individuals be kept? The answer to this question would depend on the illness, type of exposure, and risk of contracting the disease, but in general, places of quarantine should never include correctional facilities. How are quarantined individuals monitored? How long can they be kept in quarantined conditions without symptoms before it is determined that they pose no public health risk? Quarantine laws should be sufficiently flexible to be amended according to updated knowledge about modes of transmission in the case of new or emerging infectious diseases. Quarantine measures should not be one-size-fits-all but modified according to scientific evidence relating to the disease in question. Transparency in all government communications about quarantine regulations must be standard in all cases. Most importantly, science should determine when to utilize quarantine. In order to quarantine an individual, the mode of transmission must be known, transmission must be documented to be human to human, the illness must be highly contagious, and the duration of the asymptomatic incubation period must be known. Without these scientific guidelines, quarantine may be subject to serious and unjust abuse.

In the case of infectious diseases with long incubation periods, quarantine laws can be an effective means of containing possible epidemics. Similarly, in cases in which isolation alone is not effective in containing an infectious disease outbreak, quarantine might be useful. In the case of the 2003 SARS outbreak, measures that quarantined individuals with definitive exposure to SARS were effective in preventing further infections, although mass quarantines, such as the one implemented in Toronto, were relatively ineffective. Quarantine can become a serious encroachment on civil rights, but there are intelligent ways of regulating these laws to prevent such damaging outcomes. It is important not to confuse quarantine per se with the abuse of quarantine. At the same time, when quarantine has the capacity to marginalize certain populations and perpetuate unwarranted fear of foreigners, scientific certainty is essential before implementation.

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