Still reeling from the devastation wrought by this week's earthquake, the people of Haiti now face another foe, unseen but potentially just as deadly.
Pestilence, one of the apocalyptic horsemen that follow in the wake of any natural disaster, is silently lurking, waiting to strike.
Contaminated water, untreated festering wounds and disease-carrying insects could all combine to further ravage the population with a host of diseases, experts say.
"It's a very serious problem and there could be in theory -- and it's only theoretical -- there could be thousands of people who do badly, they die or become very ill," said Dr. Jay Keystone, a tropical disease expert at Toronto General Hospital.
The impoverished country has been plagued by water- and mosquito-borne diseases for years, in large part because of poor health-care and inadequate infrastructure, said Keystone. "But what's going to happen now, because the water (supply) is interrupted, because they're not going to have purified water, then you run the risk of enteric, or gastrointestinal, infections."
"They don't have cholera there, but they have E. coli and a whole bunch of other ones," he said, listing salmonella, shigella and campylobacter among the bugs that can wreak havoc on the intestines of people already weakened by trauma and lack of food.
"So you may see major outbreaks of enteric disease, and that could be a major problem over the next few weeks."
Dr. Bonnie Henry, an infectious disease expert at the B.C. Centres for Disease Control in Vancouver, said E. coli can be among the most deadly. Carried in feces, the bacteria can end up contaminating both water and food, she said.
"There are many different types of E. coli, so it causes everything from just an explosive, watery diarrhea to a very severe infection with bloody diarrhea and kidney failure."
Typhoid, caused by a strain of salmonella, is also a huge worry in Haiti, noted Keystone. "That can be very severe and in theory they could have outbreaks of typhoid occurring very soon, again because they're not going to have access to clean food and water."
Another threat from unclean water is the bacterium leptospirosis, which can cause infection through the skin, said Keystone. Carried by animals like rats and dogs, the pathogen is usually a problem that arises during widespread flooding.
"Right now, the good thing is there's no flooding, but again when the infrastructure goes down, there's always a possibility that people are now going to bathe in water that's contaminated."
Leptospirosis can cause high fever, meningitis, lung problems and severe kidney disease, he said. "Now that the whole ecology is turned upside-down, you would want to look for that as well."
Mosquito-borne diseases like malaria and dengue fever, which are endemic to the island nation, could also pose a risk. But fortunately, said Keystone, the earthquake struck during the dry season when breeding of the insects is minimal.
Still, dengue-carrying mosquitoes could find breeding grounds in small pockets of dirty water littered in the destruction of Port-au-Prince -- even tin cans and other strewn containers, he said. And as people move out into the countryside to escape the chaotic city, they could come in contact with another species of the insects that favour larger pools of water and harbour malaria.
"Malaria in Haiti is the killer malaria," he said. "Right now it's good luck that it's not the rainy season, so there's less likely to be transmission of this insect-borne disease. But if the ecology changes ... then you may get more cases."
While there is concern about disease spreading from so many dead bodies decomposing in the unrelenting heat of Haiti, Henry said the living pose a far greater threat.
"The reality is that most of the risk is from the survivors, not from the bodies," she said. "Most of the organisms that cause disease, they don't live very long after the body dies."
Still, blood-borne diseases like HIV and hepatitis B and C -- which affect a significant proportion of Haiti's population -- could theoretically be transmitted by handling the dead without protection or more likely in dealing with the injured.
As for those who have suffered wounds, one of the biggest threats to their survival is infection, said Henry.
"There are a lot of people who have injuries -- cuts, scrapes, deep lacerations. The risk of getting infections in those is going to be really high."
Aid organizations, including teams of doctors and nurses, are scrambling to bring the most basic of medical supplies, like antibiotics and bandages, into the disaster zone. Operations like the Canadian military's Disaster Assistance Response Team (DART) are working to bring purification systems to Haitians desperate for potable water.
But without clean water and the infection-quelling drugs, the danger of wounds leading to life-threatening conditions is critical, Henry said.
"Many of the survivors who have very serious injuries are going to succumb to infections if they don't get treatment very quickly," she warned.
"When you have a serious wound like that, they can cause very serious infections. It can lead to gangrene, depending on where it is, or it can lead to blood poisoning, septicemia, and people dying very rapidly from that."
"So time is of the essence."
With so many Haitians left homeless by the earthquake, refugee camps will be needed to provide shelter for thousands of people. But Keystone said gathering large numbers of malnourished people in close quarters with poor sanitation also can give rise to outbreaks of disease.
No. 1 is measles, which can spread rapidly among those who haven't been immunized, especially young children, he said. "In a malnourished child, measles can be fatal."
"The potential is there for a worse outcome, but I think with aid organizations moving in quickly ... I think they could do very well at mitigating the secondary effects of this disaster."
"The complicating factor is this is an anarchy society, that there is no security or police. And that could be major factor that could impact on the ability of the aid organizations to do their job."
