(CNN) An outbreak of contagious and deadly Marburg virus disease in the Kween district of eastern Uganda was declared by the nation's Ministry of Health on October 19.

Marburg virus disease, which causes severe viral hemorrhagic fever, ranks among the most virulent pathogens known to infect humans, according to the World Health Organization.

As of Saturday, two confirmed cases, one probable case and two suspected cases have been reported in the Kween district, on the border with Kenya, Tarik Jašarević, a spokesman for the WHO, wrote in an email. The confirmed and probable cases -- two brothers and a sister -- have died.

The first case detected by the Ministry of Health was a 50-year-old woman who died at a health center of fever, bleeding, vomiting and diarrhea on October 11. One of the woman's brothers died of similar symptoms three weeks earlier and was buried in a traditional ceremony. A game hunter, the man lived near a cave inhabited by Rousettus bats, which are natural hosts of the Marburg virus.

Laboratory tests at the Uganda Virus Research Institute in Entebbe confirmed that Marburg was the cause of both deaths.

The WHO, which is working with Ugandan health authorities to contain the outbreak, has followed up with 135 contacts of the patients, Jašarević said. Some positive news has come of these investigations: Blood tests showed no infection in two health care workers who had previously been classified as suspected cases.

Still, several hundred people may have been exposed to the virus at health facilities and at traditional burial ceremonies in the Kween district, according to the WHO.

"Marburg is a virus that is in the same family as Ebola, and it basically has very similar characteristics," said Dr. Amesh Adalja, a spokesman for the Infectious Disease Society of America. "So it spreads in blood and body fluids and thrives in areas in which people are not able to do effective infection control and take care of patients with appropriate personal protection equipment."

Although direct contact with the blood, secretions or other bodily fluids from infected people spreads the disease, touching contaminated surfaces and materials (such as clothing or bedding) may also spread the virus.

Symptoms and mortality rate

Once transmitted, the virus incubates for two to 21 days. High fever, severe headache and extreme lethargy are the most prominent symptoms, which may also include muscle aches, diarrhea, abdominal cramping, nausea and vomiting. Hemorrhaging begins between five and seven days after the fever starts. Fatal cases usually have some form of bleeding, often from multiple areas.

Patients appear "ghost-like," with drawn features, deep-set eyes and expressionless faces, according to the WHO.

On average, the mortality rate is about 50% for this hemorrhagic fever, which was first detected in 1967 during simultaneous outbreaks in Marburg and Frankfurt, Germany, and in Belgrade, Serbia. During previous outbreaks, though, fatality rates have varied from 24% to 88% depending on the viral strain and how well health authorities managed the disease, according to the WHO.

Currently, there are no treatments for Marburg virus disease.

"The medical interventions are largely going to be supportive care -- very similar to Ebola," said Adalja, a board-certified infectious disease physician. Fever control will be most important, he added, and patients may be treated with intravenous fluids and, in more advanced health care settings, electrolyte replacement.

"Those types of interventions were found to be very beneficial during Ebola," Adalja said. Some of the experimental drugs that were tried during the Ebola outbreak in Western Africa three years ago may have some effect on this virus, he said, so "on the ground, you may see some of the experimental antiviral therapies being used."

Vaccines are in development for both Marburg and Ebola, with most attention given to Ebola, though some vaccines may be beneficial in protecting against Marburg and the same family of viruses, Adalja said.

Beyond these medical obstacles, the WHO reported that it faces challenges in the form of misinformation, superstition and suspicion among residents in the areas at risk.

'Double-edged' situation

Kween district , a mountainous area 300 kilometers (about 186 miles) northeast of Kampala, boasts a total population of 93,667 people, according to the Uganda Bureau of Statistics. About a third of the population is illiterate, and just 4% of households have access to electricity. Over 90% of households grow crops, while more than 80% breed livestock. Subsistence farming is the main source of livelihood for 84% of the households.

Many people in this rural district believe witchcraft is responsible for the deaths that have occurred in their community, according to the WHO. The community members also do not hold health systems and workers in high regard, with many suspecting that health workers are deliberately killing some people to save others from the mysterious disease.

"Convincing people to go to hospital is proving a daunting task for community engagement responders," a WHO news bulletin says.

Jašarević noted, for example, one of the confirmed cases who traveled into Kenya "in search of traditional healers."

The man, a Ugandan national, crossed into Kenya at the village of Bwayi. There, medical personnel suspected that he might be suffering from the hemorrhagic fever and placed him in quarantine in Trans-Nzoia County in western Kenya as of Tuesday, health authorities confirmed. His samples were taken to the Kenya Medical Research Institute for testing.

The villagers of Kween also search caves for bat droppings, which are considered good manure for their crops.

Direct transmission from bats to humans is possible, yet the virus can also "spill between bats and non-human primates, such as monkeys, chimpanzees and gorillas, and from there it may be going into humans," Adalja said.

A few cases from animal exposure can get amplified by human transmission and other factors, such as "non-ideal infection control procedures in health care facilities," he added. "We know that burial practices, just as we saw with Ebola, can foster the spread of this virus as well." Burial practices, which include washing the deceased in preparation for funerals, facilitate contact with bodily fluids.

The outbreak, though cause for concern, is far from hopeless.

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"Although Marburg is a scary, deadly disease, it's not very contagious," Adalja said. If people are provided with protective equipment and they change their burial practices, the outbreak can be contained and extinguished.

"You have to remember that Uganda has dealt with Ebola and Marburg outbreaks for several decades. They are usually very adept at dealing with these," Adalja said. "It's not completely foreign the way Ebola was in West Africa."

For the current outbreak, prevention and containment activities are underway as health authorities continue to investigate family and community contacts.

"Public health authorities are reaching out to people and giving them actionable public health messages that they understand and can be followed," Adalja said.

The situation in Uganda is "double-edged," he said. "The fact that this outbreak is occurring in a rural area may make it harder to get resources there, but it also makes it harder for the virus to spread."