Assessment of the outbreak
The international response to the outbreak in Angola began one month ago, on 22 March. The features of Marburg haemorrhagic fever, and the conditions in Angola, have been an extreme test of international capacity to hold emerging diseases at bay. The outbreak in Angola is the largest and deadliest on record for this rare disease, which is presently showing a case fatality rate higher than 90%. For comparison, outbreaks of the closely related Ebola haemorrhagic fever have shown mortality rates ranging, according to the virus strain involved, from 53% to 88%. The only other large outbreak of Marburg, in the Democratic Republic of Congo from 1998 through 2000, had a case fatality of 83%.
Two factors make the rapid detection of outbreaks of Marburg haemorrhagic fever difficult: the extreme rarity of this disease and its similarity to other diseases seen in countries where deaths from infectious diseases are common. Neither the source nor the date of the initial cases in Angola can be presently identified with any certainty.
The number of cases began increasing in February and then, more dramatically, in March. On 21 March, Marburg virus was detected in patient samples sent to the Centers for Disease Control and Prevention in Atlanta (USA), and WHO assistance was requested by the Ministry of Health in Angola. The operational response began the following day. As known from extensive experience with outbreaks of other viral haemorrhagic fevers, including Ebola, outbreaks of Marburg can be brought to an end using classic public health interventions. In theory, the measures needed to end the Angolan outbreak are few in number and straightforward in natur