(CNN) There have been 18 more cases of illness and five more deaths reported in just two days in the Ebola outbreak in the Democratic Republic of Congo, according to the Ministry of Health. Since the outbreak began, the total number of probable cases is now 471, including 273 deaths, the ministry reported Thursday .

Public health authorities are investigating an additional 106 suspected cases, the ministry indicated.

Second-largest outbreak in history

This is the 10th outbreak since 1976 in Congo, where the virus is endemic, and the second this year. It is also now the second-deadliest Ebola outbreak in history, topped only by one in West Africa in 2014, when the disease killed more than 11,000 people.

On average, Ebola -- which causes fever, severe headache and in some cases hemorrhaging -- kills about half of those infected, but fatality rates in individual outbreaks have varied. The latest outbreak in Congo, which began in August, has a case fatality rate of 57%.

The ministry also reported that 149 people have recovered. However, 44 health workers have been infected with the virus, of whom 12 have died.

North Kivu province, which includes the cities of Beni, Kalunguta and Mabalako, remains the epicenter of the outbreak, though cases have been reported in neighboring Ituri province, according to the World Health Organization. The two provinces are among the most populated in the nation and border Uganda, Rwanda and South Sudan.

Not only is North Kivu experiencing spread of deadly Ebola, but long-term conflict smolders there, with 50 armed groups causing intermittent violence, according to WHO.

"Responding to the Ebola virus disease (EVD) outbreak in north-eastern parts of the Democratic Republic of the Congo continues to be a multifaceted challenge," WHO said in a report Thursday.

WHO estimates that more than a million refugees and internally displaced people are traveling through and out of North Kivu and Ituri, and this movement is a potential risk factor for the spread of Ebola. Another complication: a high number of malaria cases in the region.

Gender imbalance

Women and children are disproportionately sick in the Ebola outbreak, WHO reported Thursday . To date, females accounted for 62% of overall cases in which a patient's sex was recorded, while children younger than 15 accounted for 24% of cases.

The "multitude of factors" that probably contributes to those imbalanced numbers include greater involvement in traditional burial practices, transmission within family groups (including between mothers caring for sick family members) and the impact of ongoing conflict in affected areas, according to WHO.

"Of note, 46% of female cases (84 of 181) reported having attended funerals, in contrast to 31% of male cases (37 out of 118)," WHO noted. The health ministry is working with UNICEF and other partners to reduce the numbers of women and children infected.

The ministry also reported that more than 41,000 people have been given an experimental vaccine since early August. The rVSV-ZEBOV vaccine, made by pharmaceutical company Merck, proved highly protective against the deadly virus in a major clinical trial conducted during an outbreak in Guinea, according to WHO.

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Fresh guidance issued Thursday by the Pregnancy Research Ethics for Vaccines, Epidemics, and New Technologies Working Group, an international team of 17 experts, seeks to ensure that pregnant women are no longer excluded from receiving vaccines against emerging infectious diseases.

The public health preparedness report, which offers concrete steps for equitably addressing the needs of pregnant women, includes 22 total recommendations. One is that during an epidemic, such as the current one, the default setting should be to offer vaccines to pregnant women, not the reverse. Another suggestion is that decisions about whether to offer pregnant women vaccines should consider the risks faced by pregnant women and their babies if vaccine is denied and not just the potential risks of the vaccine.