The Tribune

"A widespread outbreak of dengue fever (has) occurred...The disease made its appearance in New Providence in October and spread rapidly. Unless the most stringent measures are taken to control the breeding of (the Aedes aegypti) mosquito, outbreaks of the disease may be expected from time to time."

TOUGH CALL

By LARRY SMITH

THAT account appeared in a 1927 report by Sir Wilfred Beveridge, a top British expert who reviewed public health conditions on New Providence after several tourists died of typhoid. At the time, sanitation conditions on the island were appalling.

But Beveridge's 1927 comment could just as easily have applied to New Providence last summer, when Bahamians had to deal with an unusual epidemic of dengue fever, and the hysteria in some quarters was palpable.

From online discussions and radio talk shows, you would have thought there was a conspiracy afoot to kill Bahamians that the government was desperately trying to cover up. And now, social media sites are already buzzing with concern about a possible new outbreak this year.

Nassau has suffered regular dengue outbreaks in every decade since 1978. But the severity of last year's epidemic, combined with the pervasive culture of social media and talk radio, produced an unprecedented spike in public concern.

This is not just happening in the Bahamas. Experts say dengue is one of the world's most aggressive infections, and is now rampant in all warm climates. Incidence of the disease is rising across the Caribbean and Latin America. And its fatal form, dengue hemorrhagic fever (DHF), has appeared in many countries (although not the Bahamas so far).

Globally, dengue and DHF case counts have been rising steadily for more than 50 years. DHF cases as a percentage of total dengue cases are now about 2.4 per cent, and these have a mortality rate of 26 per cent. Epidemic cycles occur every three to five years, experts say, and over time, the peaks have become progressively higher.

Before 1970, only nine countries had experienced severe dengue epidemics. But the disease is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-east Asia and the Western Pacific.

Dengue is caused by any of four related viruses. The mosquito that spreads the virus, Aedes aegypti, was dispersed from its ancestral African home by shipping and the slave trade more than 400 years ago. It has since adapted to human domestic environments, and increasing urbanization is thought to be a major factor in its spread.

The mosquito lives within a 300-foot radius of where it was born and breeds in clear water collected in buckets, tyres and other open containers.

Although asymptomatic and mild cases are common, classic dengue fever is clinically similar to the flu. DHF and its severe or fatal form, dengue shock syndrome (DSS), are complications. An important discovery in the 1960s was that DHF and DSS occurred mostly in association with second dengue infections.

Prevention relies on mosquito control programmes, which are costly and difficult to maintain, often requiring paramilitary efforts. The Pan American Health Organization's Integrated Management Strategy for Dengue Prevention includes public education, vector management, epidemiology, clinical management and environmental cleanups.

According to PAHO, dengue management demands the involvement of all sectors of the population to control the environmental factors that lead to the breeding of the mosquitoes.

In 2011, the number of dengue cases and deaths in Latin America and the Caribbean broke previous records, with outbreaks in Paraguay, Panama, Aruba, and Saint Lucia, as well as the Bahamas. Over a million cases were reported to PAHO throughout the region, including more than 700 deaths.

Bahamian health officials confirmed some 7,000 dengue cases last year, representing about 20 per cent of those who actually contracted the disease (but had mild or no symptoms). At least one death was confirmed by autopsy, and several others were under investigation by the time the outbreak subsided in the fall.

The official response to the outbreak was monitored by PAHO and included the opening of peripheral clinics with extended hours, especially weekends, to relieve the strain on the Princess Margaret Hospital. Other measures included daily fogging of populated areas with insecticide; public awareness programmes and health inspector visits to inner city neighbourhoods.

Dengue fever epidemics are a matter of rising public health concern in the Bahamas, because there are few treatments and the health system is not set up to cope with such a burden. There is also grave concern about the economic impact of dengue outbreaks, which can deter tourists from visiting.

The Aedes mosquito is common in The Bahamas, and Bahamian residents who are infected in other countries, become reservoirs for the virus. Humans are infected when a female mosquito takes a blood meal from an infected human host, and then bites an uninfected person.

In an online article in the College of the Bahamas' International Journal of Bahamian Studies last November, microbiologist Sherrie Bain called for the establishment of a national infectious disease research centre to help develop drugs and vaccines for diseases like dengue and HIV.

"The College of The Bahamas cannot shoulder (this) monumental task (of) research and innovation alone. This is an objective that will require the participation and partnership of multiple governmental and private organisations," she wrote. It would also provide "the infrastructure to train and retain Bahamian scientists who wish to pursue careers in infectious disease research but who currently have to do so at institutions and organisations overseas".

Last year, there was a crescendo of fear about the dengue outbreak. Critics said the government wasn't doing enough to combat the virus, and some even suggested that health officials were covering up deaths. Dengue infections can be life-threatening when they occur in individuals with asthma, diabetes and other chronic diseases.

Former Health Minister Dr Hubert Minnis dismissed these claims. "When someone who has dengue dies, that death is not necessarily attributed to the virus. It could be caused by other factors. We are not covering up or hiding the number of deaths. In fact, I have asked the public to inform the Ministry of any suspicious cases so that we can have them investigated," he said at the time.

But now it is responsibility of the Christie administration's newly appointed Health Minister, Dr Perry Gomez, to manage this year's response to a prospective dengue outbreak. Appropriately enough, Gomez is a specialist in infectious diseases, who ran the National HIV Programme until his recent retirement from the public service.

At least one case of dengue fever in New Providence was confirmed by the Ministry of Health in February, and as the rainy season sets in we should expect to see more cases. But the new government has yet to provide a comprehensive public report on the outlook for this dengue season.

Clearly, governments will have to pay much more attention to this expanding public health threat. The economic and social consequences of more frequent epidemics could be severe. In fact, health experts warn that the spread of dengue fever could prove more costly and cause more illness worldwide than malaria does.

There is currently no real alternative to mosquito control, although many experts think such efforts are ineffective. Nevertheless, social mobilisation and communication programmes are considered vital for dengue fever prevention and control.

According to a recent article in the journal Nature, "Dengue is now a global threat and is endemic or epidemic in almost every country in the tropics. While we wait for new tools such as vaccines, antiviral drugs and improved diagnostics, better use should be made of the interventions that are currently available".

Those interventions include preventing mosquitoes from accessing egg-laying habitats by environmental management; disposing of solid waste properly and removing man-made habitats; covering, emptying and cleaning domestic water storage containers weekly; applying insecticides to outdoor water storage containers; using personal household protection such as window screens, long-sleeved clothes, insecticide-treated materials, coils and vaporizers; and fogging with insecticides during outbreaks.

The good news is that several live virus vaccines are in the works. One under development by Sanofi Pasteur could be ready in a few years. And Cuban scientists have just announced a clinical human trial for a prototype non-live vaccine that they say has proven effective in monkeys.

• What do you think? Send comments to larry@tribunemedia.net or visit www.bahamapundit.com.