Unusual Ebola strain kills 23 in Uganda; no vaccines, treatments available

Health officials in Uganda are scrambling to catch up to a burgeoning Ebola outbreak caused by a lesser-seen Ebolavirus species called Sudan virus (SUDV), for which there is no vaccine or treatment.

Information so far suggests that the outbreak response efforts may be three weeks behind the initial spread of SUDV, which has an incubation period of up to 21 days and a case fatality rate between 41 percent and 100 percent. So far, 36 cases (18 confirmed, 18 probable) have been identified, with 23 deaths. Health officials have listed a total of 223 contacts.

But that number is likely an undercount. Several transmission chains have not been tracked, and some health facilities that saw Ebola patients did not follow optimal infection control measures, the World Health Organization warned. Further, because of the delayed recognition of the outbreak, some patients were buried in traditional ceremonies with large gatherings that could have allowed the virus to transmit further.

Yet another complicating factor is that the outbreak has been detected among those living around an active gold mine, which relies on a highly mobile population. "The declaration of the outbreak may cause some miners already incubating the disease to flee," WHO warned, possibly enabling the disease to spread to new areas.

In an outbreak update Monday, the WHO assessed the risk of spread through Uganda to be high given the multiple concerning factors.

Evolving situation

The concern is yet higher because there is no licensed vaccine or treatment for SUDV, as there is for the more common species of Ebolavirus, Zaire. Currently, there are two vaccines and two treatments for Ebola disease caused by the Zaire species, which has caused nearly all the Ebola outbreaks documented and all of the largest outbreaks. In addition to Zaire and SUDV, there are four other rare Ebolavirus species: Bundibugyo, Taï Forest, Reston, and Bombali.

Of the 41 outbreaks WHO lists on its website, SUDV was responsible for only seven, the most recent of which was in 2012. That outbreak, also in Uganda, involved seven cases and had a fatality rate of 57 percent.

The current outbreak came to light with the death of a 24-year-old man on September 19 in central Uganda. The man developed a range of worrying symptoms on September 11, which included a high-grade fever, tonic convulsions, blood-stained vomit and diarrhea, loss of appetite, pain while swallowing, chest pain, dry cough, and bleeding in the eyes. He sought care at two different private clinics to no avail and was eventually referred to a Regional Referral Hospital (RRH) on September 15. There, health care workers suspected he had a case of viral hemorrhagic fever, isolated him, and collected blood samples for testing. On September 19, the Uganda Virus Research Institute (UVRI) in Kampala confirmed he had an SUDV infection—the same day he died. Ugandan health officials declared an outbreak the next day.

Now, a week later, the case count is up to 36, with 23 dead and the remaining 13 confirmed cases still hospitalized. The median age of the cases is 26 years, with ages ranging from 1 year to 60 years.

For now, the WHO assessed this outbreak's overall regional and global risks to be low. However, the agency noted that the outbreak's scope is not yet known, and cross-border spread cannot be ruled out.