Influenza Compared to Ebola

Introduction

Influenza and Ebola are viruses capable of causing life threatening human diseases with high morbidity and mortality. Ebola virus is a viral hemorrhagic fever disease characterized by an initial non specific symptoms following by internal and external bleeding and death if not treated adequately. Both viruses are notorious for causing pandemics with loss of human life (1, 2).

Epidemiology/Outbreaks

It has been estimated that more than 200,000 deaths occur annually from influenza virus with infants and elderly worst hit by the virus. In past years, 3 subtypes of influenza virus scourged mankind causing pandemics and death. The Spanish flu in 1918 killed more than 35 million people worldwide. It has been said to be the worst influenza pandemic. Other influenza virus epidemics occurred in 1957 (H2N2, Asian flu) and 1968 (H3N2, Hong Kong flu) killing about 2 million and 700,000 humans respectively. Ebola virus causes outbreaks of viral hemorrhagic (2).

Current outbreak of Ebola has ravaged West Africa affecting humans in countries like Liberia, Sierra Leone, Guinea and Nigeria. Ebola cases have also been recorded in USA and other European countries. Current death toll in the 2014 Ebola outbreak has reached about 4,500 deaths with more than 5,000 laboratory confirmed cases. In past years, Ebola outbreaks have been recorded in parts of West and Central African claiming hundreds of life (5).

Mode of Spread

Influenza virus is spread via air droplets inhaled into the lungs. It is a highly contagious airborne disease. Influenza virus is species specific but certain strains can be transmitted from animals to man e.g. H1N1 (swine flu), H5N1 (avian of bird flu). Primary cases of Ebola virus disease is probably from contact with body fluids and secretions from host like bats, primates and from consumption of bush meat. Transmission via human to human occurs when contact with body fluids and secretions during full blown illness. Medical personnel and caregivers have a higher risk of getting infected with Ebola virus (1, 2, 6).

Microbiology

The structure of influenza and Ebola virus is distinct. Influenza virus is a single stranded RNA virus belonging to Orthomyxoviridae family. It is enclosed with a capsule and its core RNA proteins differentiates this viruses into 3 distinct groups i.e. type A, B and C influenza viruses. In case of influenza virus certain proteins e.g. neuraminidase and hemagglutinin account for its virulence and ability to cause disease. Characteristic features of influenza virus are antigenic shift and antigenic drift causing evolution of new strains.

Ebola virus is a RNA virus belonging to Filoviruses with 5 isolated species namely Zaire Ebolavirus, Sudan Ebolavirus, Tai Forest Ebolavirus, Reston Ebolavirus, Bundibugyo Ebolavirus. Taxonomy was made based on the location of the primary index case of each viral strain (2, 5).

Clinical Features

Influenza virus incubation period is 1 to 4 days while Ebola virus incubation period ranges from 1-21 days. Symptoms of influenza infection depend primarily on the viral strain. However, common symptoms include: fever, generalized body pains, sore throat, mucus discharge from the nose, headache, anorexia, nausea and vomiting, cough, chest pain and difficulty in breathing may also occur. In contrast, symptoms associated with Ebola virus infection may include: anorexia, nausea and vomiting, body and joint pain, passage of bloody diarrhoea with internal bleeding, later features like difficulty in breathing, low blood pressure and coma. (2, 5, 6).

Prevention/ Treatment

Immunization using influenza vaccine provides protection from the disease. However, immunity is only conferred to the specific strain the individual was immunized. Till date, no vaccine has been created for avian flu. Drugs like oseltamivir, Zanamivir and amantadine are administered to patients as chemoprophylaxis. Symptoms of flu are self limiting but specialist care should be provided with severe complications. Neither specific treatment nor vaccine is available for Ebola disease. Cases of Ebola disease are treated symptomatically with supportive treatment including fluids and electrolyte balance, adequate nutrition, isolation nursing and care (3, 4, 6).

References

  1. Gu Y, Komiya N, Kamiya H, Yasul Y, Taniguchi K, Okabe N. Pandemic (H1N1) 2009 transmission during presymptomatic phase. Japan. Emerg Infect Dis. Sep 2011;17(9)1737-9
  2. Clinical management of human infection with avian influenza A (H5N1) virus. World Health Organization
  3. Grohskopf et al. Prevention and control of seasonal influenza with vaccines. Recommendations of the advisory committee on immunization practices (ACIP)-United States, 2014-15 influenza seasons. MMWR Morb Mortal Wkly Rep. Aug 15 2014;63(32):691-7
  4. Hayden FG, Atmar RL, Schilling M, Johnson C, Poretz D, Paar D. Use of the selective oral neuraminidase inhibitor oseltamivir to prevent influenza. N Engl J Med. Oct 28 1999;341(18):1336-43
  5. Evaluating patients for Ebola: CDC recommendations for Clinicians. Medscape medical news. Oct 3 2014. Available at
  6. Roddy P et al. Clinical manifestation and case management of Ebola hemorrhagic fever caused by newly identified virus strain, Bundibugyo, Uganda, 2007-2008. Plos One. 2012;7(12):e52986