Today is World Malaria Day, and the World Health Organization has launched a new initiative, dubbed T3: Test, Treat, Track. It urges countries where malaria is endemic to test every suspected malaria case, treat every confirmed case with anti-malarial medicine, and track the disease with “timely and accurate surveillance systems.” The good news is that scaled-up malaria prevention and control efforts — including delivery of 145 million insecticidal bed nets in 2010 alone — have saved a million lives over the past decade. But, the WHO points out, there’s still a long way to go in combating this disease:

A massive acceleration in the global distribution of mosquito nets, the expansion of programmes to spray the insides of buildings with insecticides, and an increase in access to prompt antimalarial treatment has brought down malaria mortality rates by more than a quarter worldwide, and by one third in Africa since 2000. But simply maintaining current rates of progress will not be enough to meet global targets for malaria control.

… malaria transmission still occurs in 99 countries around the world, and the malaria burden continues to cripple health systems in many African countries. In 2010, this entirely preventable and treatable disease caused an estimated 655 000 deaths worldwide. About 560 000 of the victims were children under five years of age, which means malaria killed one child every minute.

“Sustaining recent gains in Africa will require continued political commitment and funding,” said Dr Thomas Teuscher, Executive Director a.i., Roll Back Malaria Partnership. “An estimated 3 million lives can be saved between now and 2015, if we continue to work in partnership and if governments in endemic countries redouble their efforts to provide people with essential health services.”

A literature review just published in BioMed Central’s Malaria Journal (Malaria resurgence: a systematic review and assessment of its causes, JM Cohen et al) warns that resurgence of malaria is likely when control programs weaken. The authors identified 75 resurgence events documented since the 1930s and categorized them according to suggested causes. (Causes were suggested in the articles reviewed, and the reviewers assessed the degree of supporting evidence.) The authors found:

Almost all resurgence events (68/75 = 91%) were attributed at least in part to the weakening of malaria control programmes for a variety of reasons, of which resource constraints were the most common (39/68 = 57%).

They give several examples of instances in which malaria rates jumped following the weakening of control programs, and shifting donor priorities played a role in several program weakenings (references ommitted):

The reliance of malaria programmes on a few major donors has meant that any change in donor priorities may put continued suppression of malaria at risk. A US-led campaign in Monrovia, Liberia, caused hospital admissions at the public hospital to decrease by about 95% between 1945 and 1947. Thereafter, the programme was deemed too expensive, the budget was cut by 80% in 1948, and by 1950 an assessment concluded that control measures were no longer having any impact on transmission. In Zanzibar, a USAID project in the 1980s was terminated, despite having about $US 1 million in undisbursed funds, due to the perception that the project was a failure, and malaria rates on the island of Pemba rose from 23.2% in 1989 to over 60% in 1994. In Ethiopia, funding from USAID and WHO was halted in 1974 following the overthrow of the government by a military regime. DDT application to households plummeted from a 1974 peak of 117,040 houses to only 8,139 houses in 1985. Incidence increased from 1.1 cases per 1,000 person-years in 1980 to 65.9 cases per 1,000 person-years in 1989. Similarly, in Indonesia, a DDT programme protecting 17 million people by 1959 was scaled back following withdrawal of assistance from the USA during a tumultuous political period in the early 1960s, and malaria increased from <6,000 cases in 1963 to 346,000 in 1973.

One of the challenging aspects of public health is that investments often have to continue in order to maintain progress. Sometimes, a lot of money and hard work over the course of several years can eradicate a disease worldwide, as was the case with smallpox. Countries can succeed in stamping out specific diseases within their own borders — CDC credits a 1947-1951 campaign with eliminating malaria in the US — but climate disruption can threaten such achievements (see Kim Krisberg’s post last month about about the re-emergence of dengue in Florida). With some diseases, we have to continue prevention efforts indefinitely, even after cases have become rare; consider how quickly we can see new measles outbreaks once vaccination rates falter.

Just because we’ve stopped seeing so many cases of a disease doesn’t mean we can stop devoting resources to prevention, surveillance, and response capabilities. If we do, public health will suffer. That’s true for malaria and for many other diseases.