Presentation on theme: "Arboviral Diseases Stephen J. Thomas, MD"— Presentation transcript:
1Arboviral Diseases Stephen J. Thomas, MD Director, Viral Diseases BranchWalter Reed Army Institute of ResearchJUL 2013Paul B. Keiser, Feb 2014UNCLASSIFIED
2What is a virus?Defined: A sub-cellular agent consisting of a core of nucleic acid surrounded by a protein coat that must use the metabolic machinery of a living host to replicate and produce more viral particles.Viruses are known to infect almost all organisms, including bacteria, fungi, plants, insects, and vertebrates.nm in diameter; a “filterable” agent.What is a virus? Well the name suggests that it is something toxic or “virulent.”At one point (end of the 19th century) they were called “filterable agents” to distinguish them from bacteria which were large enough to be retained by the filters used in laboratories at the time (Chamberland filters). This picture here shows the relative differences in size between bacteria and virus. Viruses are generally too small to be seen with a light microscope.Viruses can only replicate within other cells and are known to infect cells from all types of organisms: bacteria, fungi, plants, insects and animals.
3This shows an individual virus particle or “virion This shows an individual virus particle or “virion.” This is essentially a package of DNA that is enclosed in an envelope. Surface proteins determine what cell types it will infect.
4Arboviruses are Arthropod-borne. What is an arbovirus?Arboviruses are Arthropod-borne.They are transmitted to vertebrates by hematophagous (blood feeding) arthropod vectorsmosquitoesother biting fliesticksSo the term “arbovirus” does not refer to a structural family. As you saw on the earlier slide, viruses from several different structural families are transmitted by arthropods.
5Occur in nearly all parts of the world. ArbovirusesOccur in nearly all parts of the world.Over 500 distinct viruses, ~100 causing human infectionsNearly all arboviruses fall into one of 4 families:FlaviviridaeTogaviridaeBunyaviridaeReoviridae
6Classification Scheme This chart shows the different classifications of RNA viruses. Here you can see viruses that are already familiar to you (rabies, flu, dengue) arranged by family. This talk will focus on the “arboviruses,” which are almost all RNA viruses and come from these families: bunyavirus, flavivirus, reovirus, togavirusNote that when we refer to viruses as “families,” we are not necessarily talking about phylogeny in the same sense as with higher species.Source: Flint et al Principles of virologyIntroduction to Virology
7Classification Scheme Nucleic acidSymmetry of capsidNaked or enveloped------Genome architecture----Baltimore classFamily nameVirion polymeraseVirion diam. (nm)Genome size (total in kb)-Properties Classification criteriaHere are the DNA viruses, which include other familiar viruses like smallpox and herpes which is very familiar to some of you.Source: Flint et al Principles of virology
8Factors in Arboviral Disease VirusVectorEcologyHostReservoirEcologyWhat the arboviruses do share is a complex life cycle that involves multiple species. Here is this three-way interrelationship that characterizes vector-borne diseases that I showed earlier.
9Arbovirus FeaturesAble to replicate in both the arthropod vector and the vertebrate (bird or animal) host.Transmission to vertebrate occurs as the vector regurgitates while taking its blood meal.Viremia must reach high enough levels in the host to continue the cycle before reduced by the host immune system.Able to infect multiple species of animals and birds, but usually limited to a specific arthropod vector.So just because a mosquito bites 12 different species doesn’t mean that the virus will replicate enough in all 12 to maintain its life cycle.
10Arbovirus Features In the tropics, transmission is year-round. In temperate climates, transmission to vertebrates is seasonal and the virus requires an overwintering strategy.Transovarial transmission in the vector.Migration with avian host.Disease is usually more severe in newly exposed hosts and species.DeforestationIrrigationUrbanizatiomTravelIn the tropics, the vector is active all year round and transmission is on-going. But in temperate climates, the arthropod becomes less active, the blood meals stop, and the virus must have a strategy to perpetuate itself. This can be to infect the next generation of arthropods trans-ovarially, which means mother to offspring, or to infect migrating birds.Note that when a virus first enters a new species, the disease is generally more severe than what is seen in the reservoir species. This is a common theme and not unique to viruses. The virus doesn’t want to “kill” you, it wants to survive which usually means *not* killing you. But when it first enters a new species it hasn’t figured out how to gently infect.
11As a result of involving multiple species, a lot of factors that affect those other species, such as predators and climate, can affect the spread of arboviral disease.
12How do you determine if a vector is involved? Four criteria establish vector competence:Isolation of the disease-producing agent from wild- caught specimensDemonstration of its ability to become infected by feeding upon a viremic hostDemonstration of its ability to transmit by biteField evidence confirming association of the infected arthropod with the vertebrate population in which the infection is occurring.From Harley 2001, these are four criteria to establish the vector competence of a mosquito species.The reference provided is Sudia, W. D., V. F. Newhouse, and W. A. Chappell Venezuelan equine encephalitis virus-vector studies following a human case in Dade County, Florida, Mosq. News 29:596–600.
13Hundreds of arboviruses have been identified thus far Hundreds of arboviruses have been identified thus far. The CDC maintains an on-line catalog to accommodate the growing list.
14Arboviral diseases: clinical syndromes Systemic Febrile IllnessChikungunya, O’nyong-nyong, Ross River, Dengue, ZikaFever with ArthritisChikungunya, Ross River, O’nyong-nyongEncephalitisJE, WNV, TBE, EEE, WEEHemorrhagic FeverYellow Fever, Dengue, Rift Valley Fever, Chikungunya, CCHFArboviral diseases generally occur as one of the following…Note that these disease syndromes overlap and are not specific to the d\ifferent structural families of arboviruses.Togavirus (blue), Flavivirus (gold), Bunyavirus (brown)
15Arboviruses Family Flaviviridae Genus Flavivirus Tick-borne viruses Mammalian tick-borne virus groupKyasanur forest disease virus (KFDV)Tick-borne encephalitis virus (TBEV)Mosquito-borne virusesDengue virus groupDengue virus (DENV)Japanese encephalitis virus groupJapanese encephalitis virus (JEV)Murray Valley encephalitis virus (MVEV)St. Louis encephalitis virus (SLEV)West Nile virus (WNV)Yellow fever virus groupYellow fever virus (YFV)Zika VirusDengueNow moving on to the flaviviruses. These can be divided according to the vector, whether they are tick-borne or mosquito borne.Tick borne encephalitis is endemic in parts of Germany, so our allies in the Bundeswehr all get vaccinated. Among the mosquito-borne viruses you can see some familiar names.
16Threat Assessment – ID Risk Disease2010 COCOM panelID-IDEALMalaria12Dengue3Diarrhea, bacterialMDR wound pathogens4NALeishmaniasis519Q fever (Coxiella burnetti)626Norovirus / viral diarrhea7Influenza8Leptospirosis10Diarrhea, protozoal11TB12CCHF13HIV14HFRS1517Chikungunya16Meningococcal meningitis20Plague1827RickettsiosesViral encephalitidesThis is the IDEAL, a list of top military threats, as of Not that Chikungunya virus is not only in the top 20, but also on the rise. Because of its importance, we will have a whole separate talk on dengue.
17Japanese Encephalitis (JEV) Most common cause of viral encephalitis worldwide160,000 reported cases 196616,000 reported in 1996, decline is due toLarge-scale vaccination programs in ThailandUrbanization in Japan, Taiwan, ROKAnnual est > 50K2.5 cases/10,000 population at riskPrimarily a disease of childrenNaïve adults at risk -- i.e., travelersMost infections are subclinical/self-limitedClinical cases have high mortality, morbidityCFR ~25 -30%Long-term disability %First Japanese encephalitis. This is a leading cause of viral encephalitis, but the incidence is declining thanks, in part, to effective vaccination programs. Most infections are asymptomatic, but those who do get sick get very sick. So 2.5 cases per 10,000 population is actually a significant incidence, but the key here is population *at risk.* Many people living in endemic areas are not at risk because they had it as a child and are now immune.
18JEV - Clinical Findings Incubation period 4 – 14 daysSudden onset fever, chills and achesLethargy, HA, meningismus, N/VAcute Flaccid ParalysisRapid onset paralysis despite normal consciousnessWeakness legs > arms, asymmetricFlaccid paralysis also occurs in 5%-20% of comatose patients with "classic" JECourseOccasionally fulminantShort prodrome, deep coma, respiratory depression, posturing, deathUsually, improvement over ~ 1 weekNeuropsychiatric sequelae resolves over years or is permanentLong-term sequelae is a common theme.
19JEV - Transmission Vector: Culex mosquitoes Culex tritaeniorhynchus Breeds in marshes, rice paddiesNight-bitingZoonotic amplificationDomestic pigsMigratory waterfowlDomestic waterfowl?DucksSeasonal/climate factorsSummertime / post-rainy seasonIncreased vector number, feeding behaviorsIncreased viral replicationHere is the mosquito vector. It breeds in marshes and rice paddies, which accounts for the rural distribution of disease. Note that there is a seasonality to infection. This was particularly significant in defining risk to travelers back when the vaccine had such significant side effects.
20On this map, the areas in yellow are the higher incidence areas On this map, the areas in yellow are the higher incidence areas. But for JEV, higher incidence still means less than 1% of the unvaccinated.
21JEV - Prevention Vector control – difficult in endemic regions Impractical, historically ineffectiveTwilight-biting, marsh-breeding mosquitoesReservoir control – difficult in endemic regionsSwineSegregation impracticalvaccination expensiveOther potential reservoirsVaccinationMass pediatric vaccinationsApparently highly effectiveTo prevent disease, you can control the vector and you can control the reservoir. But the most effective is vaccination. This graph from the Thai Ministry of Health shows the incremental effect of these measures, and you can see the disease incidence is not affected until vaccination is done on a large scale.
22West Nile Virus Widely distributed; Infects >300 bird species Infects >60 mosquito speciesTransmission by blood product transfusion documented before routine screening.Most infections are sub-clinical/self-limited.1:5 develop fever1:150 develop CNS diseaseIncidence increases with age.
23Yellow FeverFinally, yellow fever. The virus that made Walter Reed famous.
24Yellow Fever Virus Molecular sequencing 1 serotype, 5 genotypes Phylogenetic analysesEvolved over 3000 yrsYF virus originated in AfricaDivided into West and East African lineagesWest African lineageImported into S. America and New World
25Yellow Fever Transmission Urban, sylvatic and savannah cyclesNon-human primates can be a reservoir.Aedes spp. Haemagogus spp.(Africa) (Americas)Vertical transmission, infected ova survivalIn Africa there are urban, sylvatic and savannah cycles that are maintained by different species of Aedes mosquitoes. In South America, there is just the sylvatic cycle. Overall the disease burden is much less in South America.
29Yellow Fever: Acute Period Incubation of 3 to 6 daysClinical spectrum of diseaseMild, febrile illness → Fatal VHFSevere YFFever, Chills, HeadacheLumbosacral pain, MyalgiaAnorexia, Nausea, VomitingGingival hemorrhages, EpistaxesBradycardia despite ↑ temperature (Faget's sign)
30Yellow Fever: Acute Period Symptoms for ~ 3 days (period of viremia)Defervescence and improvement (~ 24 hours)Fever and symptoms returnVomiting, Epigastric pain, Prostration, JaundiceThis slide shows the pre-icteric phase with conjunctival congestion.
31Yellow Fever: Hemorrhagic Phase Hemorrhage“Coffee-ground” hematemesis (vomito negro)Melena, Petechiae, EcchymosesIntravascular volume depletionLiver damage/jaundiceRenal failure↑ Albuminuria↓ Urine output (UO)About 15% of infections will develop into hemorrhagic or toxic phase.
32Yellow Fever: Hemorrhagic Phase Death (in 20% to 50% of severe cases)7th to 10th day of illness↑ jaundice, hemorrhages, ↑ HR, ↓ BP, ↓ UO, ↓ Temp.Agitated delirium, Intractable hiccups, Stupor, ComaLaboratory findings↓ WBC, ↓ Plts↑ Bilirubin, ↑ Serum transaminase levels↑ PT and PTT< synthesis of clotting factors + > consumptionST-T wave changes in the electrocardiogram.The clinical picture is that of a hemorrhagic fever but with more pronounced jaundice.
33Yellow Fever: Convalescent Phase Prolonged convalescenceProfound asthenia lasting 1 to 2 weeksLate deathEnd of convalescenceWeeks after recovery from the acute illnessRare phenomenonAttributed to cardiac complications or renal failureElevations of serum transaminase levelsPersist for at least 2 months after onset of acute illness
3420-50%This shows the biphasic nature of the illness.
35Yellow Fever: Diagnosis Clinical DiagnosisExposure historyAdvanced Diagnostics:Virus Isolation (culture)Rapid DiagnosticsPCRmay not be positive late in diseaseAntibody or Antigen detection (ELISA)IgM for acute phase, coupled with convalescent antibodies (IgM/IgG)Neutralization Ab are more specific for YFExposure history should take into account travel within the incubation period (3 to 6 days) and vaccination status.
36Yellow Fever: Treatment Overview Supportive Care -- no specific therapyMaintain nutrition and prevent hypoglycemiaNG tube to prevent gastric distentionTreatment of hypotension (IVF, pressors)Supplemental oxygenCorrection of bleeding abnormalitiesDialysisTreatment of secondary infectionsTreatment of DICPROTECT FROM FURTHER MOSQUITO EXPOSURECertain medications should be avoided, such as aspirin or other non-steroidal anti-inflammatory drugs (such as ibuprofen and naproxen), because these may increase the risk for bleeding.Supportive care. Don’t make the bleeding worse with aspirin or NSAIDs. And don’t let the mosquitos bite them or they will get loaded with virus and give it to somebody else. And we talked about the vaccine in the first lecture.
37Zika virus Zika virus is an emerging arboviral infection. Like other flaviviruses it has the capacity to mutate, adapt and infect urban mosquitoes in particular Aedes aegytpi.Like dengue, we are observing an emerging human infection influenced by human migration and urban transmission.It is the first Flaviviridae of the genera flavivirus that has demonstrated sexual transmission.
38Figure 1 Approximate known distribution of Zika virus, 1947–2007 Figure 1 Approximate known distribution of Zika virus, 1947–2007. Red circle represents Yap Island. Yellow indicates human serologic evidence; red indicates virus isolated from humans; green represents mosquito isolates.
39Arboviruses Family Togaviridae Genus Alphavirus Eastern equine encephalitis virus (EEE)Ross River Virus (RRV)Venezuelan equine encephalitis virus (VEE)Western equine encephalitis virus (WEE)ChikungunyaNow we’ll go through them by family, pausing to discuss in more detail those that are most relevant to your geographical area of interest.Of the Togaviruses, several fall into the genus Alphavirus. Within this family are seven complexes: Barmah Forest virus complex, EEE complex, Middleburg virus complex, Ndumu virus complex, Semliki Forest virus complex (include Chikungunya and Ross River virus), VEE conplex and WEE complex. The name “alphavirus” derives from these being previous classified as “group A arboviruses.”Besides the Alphaviruses, the other Togavirus genus is Rubivirus, whose sole member is Rubella virus.
40Ross River VirusRoss River virus (RRV) is a mosquito-transmitted Alphavirus that is endemic and enzootic in Australia and Papua New GuineaRRV causes the most common arboviral disease in AustraliaAsymptomatic infections occur in ~30%Symptomatic infections typically include constitutional effects, rash, and rheumatic manifestationsSymptoms may last for months, longer in those with co- morbiditiesThis virus was first isolated from mosquitoes trapped near the Ross River in Queensland.In 1956 the disease was called epidemic polyarthritis.
41A febrile arthritic disease was observed in 1956 in Queensland to be reminiscent of Chikungunya, implicated an alphavirus infection.RRV was first isolated in 1959 in mosquitoes from the Ross River near Townsville. Testing of patient sera showed the most reactivity with a strain called T(ownsville)48, which was then named Ross River Virus. In 1979 epidemics were described in Fiji and the Cook Islands.
43Ross River Virus Disease RRV usually incubates for 7 to 9 daysConstitutionalFever affects from one third to one half of patientsRash, fever, and arthralgia occur in any sequenceMyalgia is commonLymphadenopathy occurs quite oftenSore throat and coryza less frequentlyDiarrhea is rareFatigue typically affects over 50% of patientsWhat is coryza? It just means inflammation of the mucous membranes and could be applied to the common cold. The joint pain and rash distinguish it.
44Ross River Virus Disease Joint manifestationsSymmetrical and acute in onsetVariable tenderness, effusions are commonPeripheral joints are predominantly involved:Ankles, fingers, wrists, and kneesRashUsually lasts 5 to 10 daysMay be the sole manifestation of infectionMainly on the limbs and trunkMaculopapular, vesicular, or purpuricThe arthritis mostly affects the peripheral joints. Rash may be the only sign.
46Ross River Virus Disease DiagnosisSerology: 4x rise in IgG over 14 daysTreatmentNo known treatment will alter the disease courseTreat symptomsNSAIDSPhysical therapy, hydrotherapy, etc.ReassuranceDiagnosis is by serology, and treatment is symptomatic.(What is hydrotherapy? Are patients immune to re-infection?)
47ChikungunyaChikungunya can also occur in epidemics and can result in a more severe disease requiring hospitalization.
48Threat Assessment – ID Risk Disease2010 COCOM panelID-IDEALMalaria12Dengue3Diarrhea, bacterialMDR wound pathogens4NALeishmaniasis519Q fever (Coxiella burnetti)626Norovirus / viral diarrhea7Influenza8Leptospirosis10Diarrhea, protozoal11TB12CCHF13HIV14HFRS1517Chikungunya16Meningococcal meningitis20Plague1827RickettsiosesViral encephalitidesThis is the IDEAL, a list of top military threats, as of Note that Chikungunya virus is not only in the top 20, but also on the rise.
49Chikungunya - Threat Assessment TravelersHistorically South and Southeast Asia, Africa.Transmission in the Caribbean confirmed in Dec 2013.MilitaryLethality low, 1-7 LDD expected,Prolonged convalescence due to arthritis.Viet Nam : 15% of FUO caused by dengue or CHIKReunion Island outbreak (French)Attack rate (~33%)Lingering clinical manifestationsFrench troops in Gabon: outbreaks inA disease doesn’t have to be lethal to be of military significance. More important is the high attack rate. If an outbreak of this occurs during a combat operation, an unit can be rendered ineffective because so many soldiers come down with symptoms at the same time.(Political circumstances(Defense Intelligence Study, DIA A [7 MAR 2012])of the Gabon deployment and effect on operations?)
50Chikungunya distribution The geographic distribution also contributes to the military significance of this virus. Should we, on short notice, be called upon to invade Australia, this virus could shut us down.
51Chikungunya -- Historical Outbreaks Outbreak of Chikungunya detected in Tanzania, Africa .Robinson and Lumsden describe Chikungunya fever.1963/64 – Urban centers in India (Calcutta); >100,000 cases, >200 deaths.Sri lanka.Vietnam and Myanmar.Indonesia.1999- Malaysia2004 – Kenya2005 – Mauritius 3,500, Madagascar, Mayotte and the Seychelles2005/ Reunion Islands: 258,000 cases (1/3 of the population). 219 deaths.Indian Subcontinent (1.3M)2007/2008 – Maldives, Pakistan, Italy, Singapore, and Australia.Thailand (54k)Cambodia, PhilippinesCaribbeanMutation- primary vector changeCurrent EpidemicGet references on this mutation/vector change.
52Historic Movement of Chikungunya This map just shows the spread in recent years.
53Chikungunya: Clinical Manifestations Clinical attack rates vary by population: 25-90%Children and older adults with co-morbidities experience largest burden of diseaseHospitalization rates up to 66%.High Case:Fatality ratiosDespite the peak number of cases occurring among adults in mid-life, the greatest morbidity occurs among children and older adults.
54Chikungunya: Clinical Manifestations This table of symptoms shows similarities to RRV, though perhaps back pain is more significant with Chikungunya.
56Chikungunya vs. DengueIn terms of distinguishing this from dengue, note that with dengue myalgias predominate (“break-bone fever”) and while with chikungunya, arthritis is more common. Abnormalities on CBC are also more common with dengue.
58Chronic ChikungunyaDistal mono- or polyarthritis; improves with NSAIDs.Frequent tenosynovitis of the hands, wrists, or ankles, sometimes leading to carpal or tarsal tunnel syndromes; highly sensitive to systemic steroids.Exacerbation of pain in previously injured joints and bones requiring painkillers.
59Chronic ChikungunyaHere you can see swollen joints.
60Chronic ChikungunyaCalcifications in shoulder tendon 18 months after infectionInflammatory osteoarthritis, foot, 5 years after infection
61Chikungunya - Treatment No vaccine or antiviral licensedIllness is usually self-limitingSymptomatic treatment onlyRest to the patient and mild movements of jointsCold compresses to inflamed jointsLiberal fluid intake or IV fluidsAnalgesics and NSAIDSConvalescence can last weeks to yearsLike Ross River virus, treatment is symptomatic.
62Arboviruses Family Bunyaviridae Genus Nairovirus Crimean–Congo hemorrhagic fever virus (CCHF)Genus OrthobunyavirusCalifornia encephalitis virusLa Crosse encephalitis virus (LACV)Bunyamwera virusGenus PhlebovirusRift Valley fever virus (RVFV)Toscana virus (TOSV)
63Threat Assessment – ID Risk Disease2010 COCOM panelID-IDEALMalaria12Dengue3Diarrhea, bacterialMDR wound pathogens4NALeishmaniasis519Q fever (Coxiella burnetti)626Norovirus / viral diarrhea7Influenza8Leptospirosis10Diarrhea, protozoal11TB12CCHF13HIV14HFRS1517Chikungunya16Meningococcal meningitis20Plague1827RicketsiosesViral encephalitidesThis is the IDEAL, a list of top military threats, as of Not that Chikungunya virus is not only in the top 20, but also on the rise.
64Crimean Congo Hemorrhagic Fever Transmitted by ticks (Hyalomma species)Milkers, shepherds, abbatoir workers.Blood from patients is highly infectious.Nosocomial outbreaks with fatalities reported.Infects reticuloendothelial system and hepatocytes.Mortality rates range from 20% to 35%Covered previously.
65Arboviruses: SummaryArboviruses represent significant threats to military readiness.Clinical presentations vary fromasymptomatic to fulminant,Monophasic to biphasic,fever +/- rash, +/- arthritis, +/- encephalitis.Treatment is supportive.A significant proportion of patients have prolonged convalescence or long-term sequelae.