Emerging and Neglected Infectious Diseases: Insights, Advances, and Challenges

Table 2

Top priority emerging infectious diseases.

Emerging disease	Crimean-Congo haemorrhagic fever	Ebola virus disease & Marburg haemorrhagic fever	Middle East Respiratory Syndrome & SARS	Lassa Fever	Nipah	Rift Valley Fever
Year of (re)emergence	(1) 12th Century,; (2) 1944-45 & 1967	Ebola: 1976; Marburg: 1967	MERS: 2012; SARS: 2002	Isolated in 1969	1998-1999	In livestock: 1910s; In humans: 1931 (all in Kenya)
Causative organism	Nairovirus (CCHF virus)	EVD: Ebola virus; MHF: Marburg virus	MERS: MERS-CoV	Lassa virus	Nipah virus (NiV)	Rift Valley Fever (RVF) virus
Type/class of organism	Virus (Bunyaviridae)	Virus (Filoviridae)	Virus (Coronaviridae)	Virus (Arenaviridae)	Virus (Paramyxoviridae)	Virus (Bunyaviridae)
Vector/animal host	Hyalomma tick,; Domestic animals	Fruit bats species; EVD: Pteropodidae; MHF: Rousettus aegypti	Not well known; camel is implicated as reservoir host	Mastomys rats	Fruit bats of genus Pteropus	(1) Mosquito species, mainly Aedes sp.; (2) Domestic remnant
Epidemiology	Fatality rate of 10–40%, at least 140 outbreaks & 5000 cases since 1967	EVD: about 50% fatality. At least 31,076 cases with 12,922 deaths since 1976; MHF: case fatality rate is up to 88%	MERS: case fatality approx. 36%; severe in people with weakened immune systems, with chronic diseases	At least 100,000 cases annually in the endemic regions of West Africa with case fatality rates of 5–10%	At least 477 people infected, 252 killed since 1998; case fatality rate of 40–70%	Commonly affects livestock, causing disease, abortion, and death in thousands of domesticated animals
Populations at risk	Endemic in Africa, the Balkans, the Middle East, and Asia	EBV: Africa; MHF: Frankfurt in Germany; Belgrade and Africa	MERS: people with chronic disease. Countries include Egypt, Oman, Qatar, and Saudi Arabia	Endemic in West Africa	Southeast Asia region	Africa and Arabian Peninsula
Mode of transmission	(1) Tick bites; (2) Zoonotic: contact with infected animal blood and with secretions or body fluids of infected persons	EBV: contact with blood, secretions, and body fluids/organs of infected (a) nonhuman primates and (b) humans; MHF: mainly human-to-human	MERS is zoonotic: no human-to-human transmission; origin and exact route are unknown	Zoonotic: (1) exposure to urine or faeces of infected Mastomys rats; (2) Direct contact with body fluids of infected person	(1) Contact with excretion and secretion of infected bats; (2) Direct contact with infected pigs	Zoonotic and Epizootic: Bite of infected mosquitoes (in humans and animals)
Clinical presentations	Nonspecific: high fever, myalgia, headache, nausea, abdominal pain, and nonbloody diarrhoea	Clinically similar: fever, severe headache, diarrhoea, lethargy, and so on; impaired kidney function, internal /external bleeding, and nervous system problems (MHF)	Ranges from no symptoms to death. Generally fever, cough, and shortness of breath; pneumonia, gastrointestinal problems, and respiratory failure	About 80% of infections are asymptomatic. Symptoms are variable: fever, cough, malaise; pains, fluid in the lung cavity, facial swelling, bleeding, and more	(1) Barking pig syndrome (in pigs); (2) In humans: fever, muscle pain; brain inflammation leading to coma	Humans: include fever, muscle/joint pain; eye disease, meningoencephalitis, and haemorrhagic fever; Animals: mortality and abortion
Pathogenesis	Not well understood	Not well understood	Not well understood	Not well understood	Not well understood	Not well understood
Diagnosis	(1) Virus isolation by cell culture; (2) Viral genome detection (RT-PCR); (3) Serology (ELISA)	(1) Virus isolation by cell culture; (2) Viral genome detection (RT-PCR); (3) Serology (e.g., ELISA)	(1) Mainly by molecular detection (RT-PCR); (2) Also serology (ELISA)	Only in reference labs: isolation by cell culture, viral genome detection (RT-PCR), and serology (ELISA & neutralization)	(1) Virus isolation; (2) Histopathology; (3) RT-PCR; (4) Serology (ELISA, neutralization)	(1) Isolation by cell culture; (2) Viral genome detection (RT-PCR); (3) Serology (ELISA)
Treatment	No vaccine available: (1) General supportive care management; (2) Ribavirin antiviral	No vaccine or specific antiviral treatment. General supportive care management	MERS: no vaccine or specific treatment. General supportive care management	No vaccine yet; (1) Early supportive care; (2) Ribavirin antiviral therapy seems effective	No vaccine available; (1) Symptoms management; (2) Ribavirin antiviral treatment	No specific treatment; generally supportive therapy
Prevention	Minimize tick burden in livestock, minimize human contact with vertebrate hosts	Awareness; EVD: good hygiene; avoid contact with blood and body fluids; MHF: protect pigs from fruit bats contact	MERS: general hygiene measures in contacting camels/other animals; avoid consumption of raw or undercooked animal products	(1) Good hygiene—in community, homes; (2) Standard infection prevention and control measures in healthcare and lab settings	Avoid contact with infected secretions, excretions, blood, or tissues of infected pigs and bats	(1) Animal vaccination; (2) Protection against vector bites; (3) Animal health surveillance

Note. Source of list: http://www.who.int/medicines/ebola-treatment/WHO-list-of-top-emerging-diseases/en/ [9].
MERS: Middle East Respiratory Syndrome; SARS: Severe Acute Respiratory Syndrome.