A second country in Africa has recently reported cases of Marburg, an infectious disease that has high fatality rates and, according to the World Health Organization, epidemic potential. The news has lent urgency to ongoing efforts to develop a vaccine for Marburg — and concern among public health officials that earth's changing climate could be fueling the outbreaks.

The first outbreak this year was reported in February in Equatorial Guinea, but WHO was concerned the country was undercounting those cases. On Wednesday, Reuters reported that Equatorial Guinea had confirmed a total of 13 cases since the beginning of the pandemic. The case count update came the same day as WHO, whose staff on the ground suspected more cases, asked Equatorial Guinea to be transparent about how many cases the country had. Equatorial Guinea has also reported 20 probable cases, all of whom have died.

About 1800 miles away, across the continent, Tanzania is also reporting a Marburg outbreak and has confirmed eight cases, including five deaths in the northwest Kagera region, according to WHO.

Marburg is a hemorrhagic fever virus, which can lead to the body's organs shutting down. Symptoms vary but usually start with a headache and fever. The host animal is believed to be the fruit bat, which often is found in caves. Bats can directly infect humans or monkeys and pigs can be infected by the bats and then those animals infect humans. Marburg is spread through direct contact (through broken skin or mucous membranes) with blood, secretions, organs or other bodily fluids of infected people and through any materials such as bed sheets that become contaminated with the infected fluids.

As is the case with Ebola, burial ceremonies have sometimes been a source of infection if people come in contact with secretions of someone who died of the virus.

Diagnosis is hard, says Dr. David Freedman, professor emeritus of infectious diseases at the University of Alabama at Birmingham, because many poor countries just don't have labs to test disease samples. In fact, while the health officer in Equatorial Guinea suspected Marburg on February 7, the viral sample had to be sent to Senegal, 2,000 miles away, and was only confirmed a week later.

The outbreak in two parts of Africa could mean climate change is playing a role. "A current concern," says Dr. Lee Hampton, an epidemiologist with GAVI, the Vaccine Alliance, "is that climate change causing new [higher] average temperatures could result in host animals for the Marburg (and other) viruses moving to areas of the world they have not been before and creating outbreaks where they have not been before."

WHO's Director General General Tedros Adhanom Ghebreyesus spoke about the effects of climate change on disease at a press conference this week. "The outbreaks of Marburg virus disease are another reminder that we can only truly protect human health if we also protect the health of animals and our planet, which sustains all life," said Dr. Tedros, adding that WHO has been working on the issue with the Food and Agriculture Organization and the World Organisation for Animal Health and the UN Environment Programme. The groups participated in a meeting at WHO headquarters last week and called for countries to "[strengthen] the policies, strategies, plans, evidence, investment and workforce needed to properly address the threats that arise from our relationship with animals and the environment."

Slowing the spread

The two outbreaks have intensified efforts to develop better treatments and a possible vaccine.

Immediately after the outbreak in Equatorial Guinea began, the WHO convened a meeting of experts to discuss possible vaccines and treatments for the virus. On Wednesday the WHO Director General announced the agency "is working to begin trials of vaccines and therapeutics as soon as possible." Dr. Michael Ryan, Executive Director of WHO's Health Emergencies Programme, tells NPR that the next step is to convene a working group to develop the legal framework for the clinical trials.

Gavi's Hampton says working quickly to develop a vaccine is critical because every outbreak is a chance for the virus to spread out of control. "If the virus spreads to larger cities, many more people can be affected, and the virus is that much harder to contain. Worldwide spread becomes a distinct possibility. That's why an effective vaccine that can be deployed at the first sign of an outbreak is needed."

Other measures can be helpful moving forward. More consistent and comprehensive monitoring could help contain future outbreaks, says Tedros.

The approach for outbreaks such as Marburg would involve coordinating scientists to routinely monitor of the virus in populations of fruit bats, bat feces and aerosols, and human populations including hospital data, bushmeat diet, and mobility of humans and animals.

Oladele A. Ogunseitan, Ph.D., a professor of Population Health and Disease Prevention at the University of California, Irvine who is involved with the WHO effort. "We currently do not have a single platform where these data are integrated, and we don't necessarily have to do this one virus at a time."

Ogunseitan says this multi-pronged approach has been used successfully with COVID-19 with the monitoring of the virus in urban wastewater, rats and deer populations to predict trends, though he adds that "the coordination has been sporadic and not as effective as it would have been if we planned it from the get go, particularly in the early stages in Wuhan Market in China."

Marburg origins

Marburg was first identified in 1967 among lab workers in Marburg, Germany, and Belgrade, in what is now Serbia. They were exposed to the virus during research with monkeys or tissue samples of the monkeys originally from Uganda.

It is "similar to many other illnesses which is why Marburg can spread before it's identified and before infected people are isolated," says Dr. Daniel Bausch, a former U.S. Centers for Disease Control and Prevention medical officer now with the non-profit FIND, which develops diagnostic tests around the world. In fact, news reports say that the first case in the Equatorial Guinea outbreak may have emerged in early January of this year but only prompted alarm in early February, when a health worker saw patients who had severe symptoms associated with Marburg, including bloody diarrhea and blood in vomit.

Another reason that it's hard to diagnose early on: People can be infected and not show symptoms of Marburg for two to 21 days, followed by fever, chills, headache and body aches. A rash can appear around day five on a person's body, and additional symptoms such as nausea, vomiting, chest pain, a sore throat, abdominal pain, and diarrhea can occur in the course of the disease. The symptoms can become increasingly severe including jaundice, an inflamed pancreas, severe weight loss, delirium, massive internal bleeding, shock and multi-organ failure. The fatality rate varies widely, but the WHO puts it around 50%.

Ogunseitan finds it encouraging that with such a high potential fatality rate from Marburg virus, public health experts have several tactics to use to try to prevent outbreaks. "These activities aim to ensure that we prepare countries to develop workforce capable of interpreting a broad range of information on early warning systems, and to collaborate to prevent outbreaks from becoming pandemics."

Fran Kritz is a health policy reporter based in Washington, D.C., and a regular contributor to NPR. She also reports for The Washington Post and Verywell Health. Find her on Twitter: @fkritz