influenza a changing human susceptibility mass immunocompromisation with hiv/aids climate change diseases transmitted by animal vectors such as mosquitoes (e.g. west nile fever) are moving further from the tropics as the climate warms changes in human demographics and travel facilitating rapid global spread sars-related coronaviruses economic development use of antibiotics to increase meat yield of farmed cows leads to antibiotic resistance war and famine clearing of animal habitats that increase the range of diseases such as ebola inadequate public health services poverty and social inequality tuberculosis is primarily a problem in low-income areas bioterrorism 2001 anthrax attacks land use dam construction and irrigation systems can encourage malaria and other mosquito-borne diseases use of indiscriminate pesticides in industrial farming reduces/eliminates biological controls (e.g. dragonflies, amphibians, insectivorous birds, spiders) of known disease vectors (e.g. mosquito, tick, biting midge) anti-vaccination or vaccine hesitancy re-emergence of measles wildlife trade has been linked to zoonotic emergence and spread of new infectious diseases in humans, including nipah virus and covid-19 crowded and unhygienic wet markets and wildlife farms have been implicated in animal-human transmission of emergent viruses, including novel coronaviruses and influenza viruses complex issues surrounding the commerce and consumption of bushmeat are also of particular concern. list niaid list of biodefense and emerging infectious diseases the u.s. national institute of allergy and infectious diseases (niaid) maintains a list of biodefense and emerging infectious diseases. the list is categorized by biodefense risk, which is mostly based on biological warfare and bioterrorism considerations. as of 2004, it recognized the following emerging and re-emerging diseases. newly recognized (since the 1980s): acanthamebiasis australian bat lyssavirus babesia, atypical bartonella henselae coronaviruses, including sars coronavirus ehrlichiosis encephalitozoon cuniculi encephalitozoon hellem enterocytozoon bieneusi helicobacter pylori hendra virus (equine morbilli virus) hepatitis c hepatitis e human herpesvirus 8 human herpesvirus 6 lyme borreliosis microsporidia parvovirus b19 re-emerging: coccidioides immitis enterovirus 71 prion diseases streptococcus, group a staphylococcus aureus diseases with bioterrorism potential, cdc category a (most dangerous): anthrax clostridium botulinum tularemia smallpox and other pox viruses viral hemorrhagic fevers arenaviruses: lymphocytic choriomeningitis (lcm), junin virus, machupo virus, guanarito virus, lassa fever bunyaviruses: hantaviruses, rift valley fever, crimean-congo hemorrhagic fever virus flaviviruses: dengue filoviruses: ebola, marburg yersinia pestis diseases with bioterrorism potential, cdc category b: brucella species (brucellosis) burkholderia pseudomallei (melioidosis) burkholderia mallei (glanders) coxiella burnetii (q fever) epsilon toxin of clostridium perfringens food-borne and water-borne pathogens bacteria campylobacter jejuni diarrheagenic e. coli listeria monocytogenes pathogenic vibrios salmonella shigella species yersinia enterocolitica protozoa cryptosporidium parvum cyclospora cayetanensis entamoeba histolytica giardia lamblia toxoplasma fungi microsporidia viruses: caliciviruses hepatitis a mosquito-borne encephalitis viruses california encephalitis eastern equine encephalitis (eee) japanese encephalitis virus (je) kyasanur forest virus lacrosse virus (lacv) venezuelan equine encephalitis (vee) western equine encephalitis (wee) west nile virus (wnv) yellow fever ricin toxin (from ricinus communis) staphylococcal enterotoxin b typhus fever (rickettsia prowazekii) diseases with bioterrorism potential, cdc category c (least dangerous): influenza multidrug-resistant tuberculosis (mdr-tb) nipah virus rabies sars coronavirus tick-borne encephalitis virus tick-borne hemorrhagic fever viruses other hantaviruses other rickettsias since 2004, niaid has added to its biodefense emerging pathogen list: yersinia pestis (plague, category a) chapare virus (category a areanavirus) lujo (category a arenavirus) chlamydia psittaci (category b) naegleria fowleri (category b) balamuthia mandrillaris (category b) st. louis encephalitis virus (slev, category b) tick-borne hemorrhagic fever viruses (category c) bunyaviruses: severe fever with thrombocytopenia syndrome virus (sftsv), heartland virus flaviviruses: omsk hemorrhagic fever virus, alkhurma virus, kyasanur forest virus (reclassified from b to c) powassan virus (deer tick virus, category c) chikungunya virus (category b) coccidioides species (category c) human coronavirus hku1 (category c) middle east respiratory syndrome coronavirus (category c) anaplasmosis aspergillus bk virus bordetella pertussis borrelia miyamotoi clostridium difficile cryptococcus gattii enterococcus faecium enterococcus faecalis enterovirus 68 jc virus leptospirosis measles mucormycosis mumps virus poliovirus zika virus (category b) niaid also monitors antibiotic resistance, which can become an emerging threat for many pathogens. who list of most important emerging infectious diseases in december 2015, the world health organization held a workshop on prioritization of pathogens "for accelerated r&d for severe emerging diseases with potential to generate a public health emergency, and for which no, or insufficient, preventive and curative solutions exist." the result was a list containing the following 6 diseases crimean–congo hemorrhagic fever filovirus diseases (ebola virus disease and marburg virus disease) highly pathogenic emerging coronaviruses relevant to humans (mers and sars) lassa fever nipah virus infection rift valley fever these were selected based on the following measures human transmissibility (including population immunity, behavioural factors, etc.) severity or case fatality rate spillover potential evolutionary potential available countermeasures difficulty of detection or control public health context of the affected area(s) potential scope of outbreak (risk of international spread) potential societal impacts newly reported infectious diseases in 2007 mark woolhouse and eleanor gaunt established a list of 87 human pathogens first reported in the period between 1980 and 2005. these were classified according to their types. numbers of pathogen species by taxonomic category number of species known in 2005 number of species reported from 1980 to 2005 total 1399 87 bacteria 541 11 fungi 325 13 helminths 285 1 prions 2 1 protozoa 57 3 viruses 189 58 dna viruses 36 9 rna viruses 153 49 major outbreaks the following table summarizes the major outbreaks since 1998 caused by emerging or re-emerging infectious diseases disease country or region year of start of outbreak ngari virus kenya, tanzania, somalia 1998 nipah virus malaysia 1998 west nile virus usa 1999 itaya virus peru 1999 rift valley fever saudi arabia and yemen 2000 eblv-2 scotland 2002 sars-cov 2002 influenza a virus subtype h7n2 2002 monkeypox usa 2003 chapare virus bolivia 2003 plague algeria 2003 htlv-3, htlv-4 cameroon 2005 melaka virus malaysia 2006 lujo virus southern africa 2008 multi-drug resistant p. falciparum south-east asia 2008 candida auris 2009 heartland virus usa 2009 bas-congo virus drc 2009 lassa fever mali 2009 pandemic h1n1/09 virus global pandemic 2009 huaiyangshan banyangvirus 2009 plague libya 2009 cholera haiti 2010 lassa fever ghana 2011 plasmodium cynomolgi malaysia 2011 h3n2v 2011 mers -cov 2012 mojiang paramyxovirus 2012 h7n9 2013 sosuga pararubulavirus 2013 h10n8 2013 chikungunya caribbean 2013 variegated squirrel bornavirus 1 2013 colpodella sp. heilongjiang china 2013 ebola virus disease west africa 2014 h5n6 2014 lassa fever benin 2014 bourbon virus usa 2014 zika virus americas 2015 crimean–congo hemorrhagic fever spain 2016 chikungunya pakistan 2016 lassa fever togo 2016 ntwetwe virus uganda 2016 monkeypox nigeria 2017 yellow fever brazil 2017 rat hepatitis e virus 2017 guinea worm chad 2018 lyme disease 2018 h7n4 2018 monkeypox liberia, uk 2018 nipah virus india 2018 covid-19 global pandemic 2019–present methicillin-resistant staphylococcus aureus methicillin-resistant staphylococcus aureus (mrsa) evolved from methicillin-susceptible staphylococcus aureus (mssa), otherwise known as common s. aureus. many people are natural carriers of s. aureus, without being affected in any way. mssa was treatable with the antibiotic methicillin until it acquired the gene for antibiotic resistance. through genetic mapping of various strains of mrsa, scientists have found that mssa acquired the meca gene in the 1960s, which accounts for its pathogenicity, before this it had a predominantly commensal relationship with humans. it is theorized that when this s. aureus strain that had acquired the meca gene was introduced into hospitals, it came into contact with other hospital bacteria that had already been exposed to high levels of antibiotics. when exposed to such high levels of antibiotics, the hospital bacteria suddenly found themselves in an environment that had a high level of selection for antibiotic resistance, and thus resistance to multiple antibiotics formed within these hospital populations. when s. aureus came into contact with these populations, the multiple genes that code for antibiotic resistance to different drugs were then acquired by mrsa, making it nearly impossible to control. it is thought that mssa acquired the resistance gene through the horizontal gene transfer, a method in which genetic information can be passed within a generation, and spread rapidly through its own population as was illustrated in multiple studies. horizontal gene transfer speeds the process of genetic transfer since there is no need to wait an entire generation time for gene to be passed on. since most antibiotics do not work on mrsa, physicians have to turn to alternative methods based in darwinian medicine. however, prevention is the most preferred method of avoiding antibiotic resistance. by reducing unnecessary antibiotic use in human and animal populations, antibiotics resistance can be slowed. scientific advisory group for origins of novel pathogens on 16 july 2021, the director-general of who announced the formation of the scientific advisory group for origins of novel pathogens (or sago), which is to be a permanent advisory body of the organisation. the group was formed with a broad objective to examine emerging infectious diseases, including covid-19. according to the who director-general, "sago will play a vital role in the next phase of studies into the origins of sars-cov-2, as well as the origins of future new pathogens."