Volume 14, Number 9
May 4 - 17, 2008

A century of tracking yellow
fever and dengue in Panama
by Eric Jackson

Panama is The Crossroads of the World, or at least likes to think of itself that way in terms of its maritime commerce and the many economic, cultural and social factors that flow from its useful geography. Intricately linked to these is our status as place where famous public health battles have been and are being fought.

Might the French, had it not been for all the financial scandals, have finished their canal but for the death toll extracted by tropical diseases? It's one of those impossible historical "what if" questions, but any honest attempt to answer it must surely factor in malaria and yellow fever as weighty economic issues that in the end made it less possible to paper over financial corruption and mismanagement.

When the Americans came to build the canal, the first thought was to pick up where the French had left off, but quickly the second thought was to stop all digging and concentrate all efforts on improving sanitation in the area in which the canal was to be built.

As Dr. Vicente Bayard, chief epidemiologist of the Gorgas Memorial Institute for Health Research, told that April meeting of the Panama Historical Society, in the aftermath of the Spanish-American War Dr. William C. Gorgas had already put discoveries by Cuban physician Carlos Finlay to scientific testing and then practical application, and in an eight-month campaign eliminated yellow fever in Havana. Notwithstanding that remarkable triumph, he faced initial resistance from the first American canal construction managers and had to fight bureaucratic battles as well as the war against the distinct mosquito vectors that spread malaria (the female Anopheles mosquito) and both yellow fever and dengue (the Aedes mosquitoes).

The French had kept fairly good health statistics, that had rubbed off on local authorities, and when the Americans came they had a pretty good idea of how many local people were dying of which diseases. 

(The big killer in Panama City in the years leading up to national independence in 1903? It was beriberi, the nutritional disease, which in turn was the product of the Thousand Day War, which devastated the countryside, destroyed crops and farm animals and sent many hungry and traumatized rural supporters of the Conservative side fleeing from the likes of Victoriano Lorenzo's Liberal guerrilla army into the capital, where the local junta couldn't feed them.)

When it came to infectious diseases, malaria was the big problem. Yellow fever, however, because of its high mortality rate and the quick and horrible ways that the disease progressed, was what caused the most panic.

Gorgas responded with "the main medical intervention of the 20th century," public sanitation. Colon and Panama City, whose streets were pestilential muddy ruts, were paved. Sewer systems were installed. Nearby swamps were drained or sprayed with oil. Even the tiniest --- especially the tiniest --- bits of standing water could and did result in fines. Garbage collection and disposal services were instituted. Gorgas even prevailed upon Catholic churches to change their holy water every day.

Malaria was greatly reduced but was hard to definitively conquer. It still is --- in 2006, it was Panama's number one vector-borne infectious disease. But yellow fever was quickly eliminated. The last death from that disease in Panama was recorded in 1905.

Once it became impossible for an Aedes aegypti mosquito to find someone with yellow fever to bite, those insects could no longer spread yellow fever. However, if someone carrying dengue fever is available to feast upon, these mosquitoes can and will spread it to someone else.

Aedes breed in tiny, clear bodies of water --- that toilet attached to the guest room that never gets flushed, the pan that captures condensed water under the refrigerator, the dish under the potted plant, the beer can thrown by the side of the road, the discarded tire or junk car and so on. It's mostly an urban dweller, but in rural areas where people don't have running water the Aedes likes to live in the containers in which people keep their household water, especially when these are not kept covered.

Anopheles are swamp dwellers, and in Panama have largely been driven to the remote areas. "Malaria only affects the poor people," Bayard said. They live where Anopheles mosquitoes are part of the environment and they don't use any protection --- things like screens --- in their housing. Panama had a major malaria outbreak from 2002 to 2006, mostly in the indigenous comarcas. Bayard attributes this largely to decentralizing moves in the public health care system and budget cuts to vector control programs.

The sanitation program in the canal area all but eliminated dengue fever along with yellow fever. A few cases persisted, and in 1942, when the isthmus was crowded with military people and sailors carrying the cargoes of war, there was a significant outbreak. But the number of cases dwindled to next to nothing in the 50s, with only the occasional isolated case identified through the 80s.

Meanwhile, the control efforts broke down and failed. Aedes mosquitoes developed resistance to the pesticides that were being sprayed on them. There was accelerated urban growth, with many rural people who had not internalized urban sanitation habits crowding into the metro area. Politicians didn't place much importance on sanitation, especially in times when there was great national and international pressure to cut costs and avoid public budget deficits. Other, scarier epidemics came along, and funding to confront HIV took priority over basic urban sanitation.

Thus in the mid-90s dengue made a major comeback to Panama --- which was part of a trend that went right through the tropical Americas and other warm-weather regions in the world. Dengue's return became hard to ignore with a major outbreak in the Santa Librada area of San Miguelito in mid-1994. We have had many reported cases, a lot more unreported cases of the usually flu-like illness, and a few deaths from the hemorrhaging that occasionally results since then.

It doesn't surprise Dr. Bayard. He points out that in Dr. Gorgas's time, there was one health inspector on the isthmus for each 1,000 people, but now that ratio is one for every 9,017. Spraying to control mosquitoes was phased out in the 1980s and to the extent that it has been brought back, has been on a small scale, mainly by the sending of trucks to spray in city neighborhoods when a dengue case has been identified there to try to keep the mosquitoes spreading the disease among immediate neighbors.

There have been education programs, but knowledge of how Aedes mosquitoes breed has not been effective at changing people's behavior, according to Bayard. More inspections and fines, he thinks, are a bit more effective.

There is, according to the epidemiologist, a possibility that genetic manipulations to breed swarms of sterile mosquitoes and release them into the wild could be more effective at eradicating the Aedes than pesticides have been. However, below new technologies, below public education and below law enforcement, Bayard says there's a bottom line. "Knowledge is not enough. If the government does not offer services --- running water supplies, proper garbage collection and so on --- we have a very bad problem."