Scary New Diseases that Seem to Come out of Nowhere

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Scary New Diseases that Seem to Come out of
Nowhere
-Diseases that kill the young and healthy
-Most are going to be zoonoses -The three I a
m going to talk about are zoonoses
-Hantavirus -SARS -Ebola
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Hantavirus Pulmonary Syndrome
Enveloped negative strand RNA virus,
now named the Sin Nombre virus
Chronic, asymptomatic infection of rodents Ex
creted in rodent urine, saliva, feces
Worldwide distribution No insect vectors S
usceptible to many disinfectants
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Hantavirus Transmission to Humans
Aerosolized rodent excreta Increase with rise o
f rodent population Infections of lab workers w
ith No person to person spread
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Hantavirus in Humans
Incubation period is 1-5 weeks
First symptoms include fever, fatigue, and muscl
e aches After a few days shortness of breath
and sometimes headaches, dizziness, nausea, vom
iting, diarrhea, and stomach pain. RAPID pro
gression-short time to death
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1993 Four-corners Outbreak
May 1993 was the first infections for the
western hemisphere Navajo nation-5 deaths of h
ealthy young adults Looking for toxins, they sa
w a lot of rodent droppings Huge increase in th
e deer mouse population that year
Found virus in the deer mouse population
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Since 1993
Cases have been found in 30 states, including
Wisconsin. As of 3/26/2007, there have been 465
cases in the US and many more in the Americas
Mean age is 38, 64 are male, and the death
rate is 35 3/4 of cases have occurred in resid
ents of rural areas
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CDC-Hantavirus Pulmonary Syndrome Cases
by Reporting State United States March 26, 2007
Total Cases (N465 in 31 States)
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How to Clean Up After Mice
Especially a problem with rural cabins, or
snow-birds houses If it is bad, open all doors
and windows for 30 min Wear plastic or rubber g
loves. Spray any areas of rodent dropping with
disinfectant or dilute bleach, and let it soak
5 min before cleaning. Mop floors and clean cou
ntertops, cabinets, and drawers with
disinfectant or dilute bleach.
Steam clean rugs and furniture, and wash bedding
if you see any rodent dropping on them.
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Severe Acute Respiratory Syndrome (SARS)
SARS first surfaced in southern China (Guangdong
province) in November 2002 and was spread around
the world by travelers. WHO says that 8098 peopl
e were sick from SARS and 774 died (10 fatality
rate). In the US there was 192 cases, all reco
vered. WHO now says that only 8 people in the US
had lab confirmed cases, and they had all
traveled to areas in the world with SARS. Air
travel and tourism were badly hit.
In China, SARS killed 340 people (190 in Beijing
) and infected more than 5300 people nationwide.
China failed to divulge the scale of contagion
for months, greatly increasing its spread.
7/29/03 Beijing announced that the last 12 SARS
patients have recovered from the disease, marking
an apparent end.
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SARS symptoms
Symptoms are initially flu-like illness rapid
onset of high fever followed by muscle aches,
headache and sore throat. Early laboratory find
ings may include thrombocytopenia (low plat
elet count) leucopenia (low white blood cell co
unt) followed by bilateral pneumonia progress
ing to acute respiratory distress
Mortality rate for younger people is between 3-6
, but about 50 for persons over 65.
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Where did SARS come from?
This question is crucial for understanding
whether the disease will reemerge
First thought was that the 1997 avian flu (H5N1)
had acquired the ability to transmit from huma
n to human, but none of the SARS patients
had any influenza (or any other known
respiratory pathogens). The search was one for
a totally new pathogen tissue culture,
sequencing, and electron microscopy -all showed
a new cornavirus. Meanwhile, epidemiologists
noted that a fairly high proportion of early
SARS patients were food handlers (animal wholes
alers, cooks, etc.) At Dongmen market, almost e
verything that's vaguely edible is for sale,
and many restaurants in the province keep live
animals on the premises and slaughter them as n
eeded. Antibodies to the SARS virus in a number
of animal market workers, but not in the wider
population. No evidence that SARS was spread
by eating infected animals.
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In Response
Chinese authorities immediately, although
temporarily, banned hunting, selling,
transporting, and exporting all wild animals.
They also quarantined all farm-raised civets in
Guangdong. WHO officials got permission the en
d of July from Chinese authorities to send in
4 teams of experienced animal-
virus hunters from the Netherlands, Australia,
US, and Japan.
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What is the Reservoir?
The researchers isolated a coronavirus almost
identical to the human SARS virus from masked
palm civets, a raccoon dogs, foxes, and cats.
Only difference was the viral RNA isolated marke
t animals was 29 nucleotides longer than viral
RNA isolated from most humans.
Beijing Genomics Institute have found 2 humans w
ho were infected with the longer variety (early
cases?). Its novel RNA sequence suggests that
this virus had probably evolved in
isolation for a long time before jumping to
humans. It is not likely that civets are the re
servoir. A more probable scenario
is that the civets picked up the virus from a
more exotic animal in the markets or holding
facilities (close quarters), or in the wild bef
ore being brought to market.
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SARS Reservoir Found in 2005
A virus closely related to SARS (92) has been
found in the -Horseshoe bat- Known that Ci
vets were not the reservoir since
-they had little immunity -they become seriousl
y ill So civets are the amplifier host
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What Causes SARS?
SARS-CoV was found in clinical and post-mortem
samples from 436 SARS patients in 6 countries.
They injected SARS-CoV into 4 macaques, 3 of w
hich went on to develop SARS-like symptoms.
No other viral or bacterial copathogen was neede
d. These experiments fulfill Kochs postulates
and prove that SARS-associated coronavirus
(SARS-CoV) is the primary causal agent of SARS.
Butable to find SARS-CoV in only 60 of sampl
es from SARS patients. One possibility is
that some people listed as cases actually had
something else that looked like SARS.
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SARS doesnt resemble the 3 known groups of
coronaviruses
Groups 1 and 2 represent mammalian viruses.
Group 3 is only avian viruses.
Coronaviruses are responsible for 30 of resp
iratory infections in humans.
K. Holmes (2003) J. Clin. Invest. 1111605-1609
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A new coronavirus why is this important?
Coronaviruses are enveloped, positive stranded,
RNA viruses with the largest genome of any RNA
virus. Good News 1) Single piece of RNA
, not segmented like flu, so it doesnt recombine
easily 2) SARS is relatively stable genome compar
ed to other RNA viruses These 2 facts should ma
ke it relatively easy to make a vaccine for SARS
In general, enveloped viruses are less stable
than non-enveloped
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Initial fear that SARS was seasonal
Science, vol 301
Lower temperatures, humidity, and ultraviolet
light during the winter may increase viral stab
ility. People huddling indoors may facilitate s
preading.
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How long do patients remain infectious?
What is the time period between infection and
onset of infectiousness?
Resurgence of cases in Toronto, 2 weeks after it
was SARS-free Some animals can shed infectiou
s corona virus for weeks to months
with no symptoms.
Dye and Gay, Science, v300, 1884
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Other Questions
How many infections will each patient produce?
Estimated that a single infection of SARS will i
nfect 3 secondary cases in an uncontrolled
population. What about the superspeaders? WHO d
efines as passing SARS 10 people
Start local epidemics. Often less deadly for them
then the people close to them.
Are current public health measures enough to bri
ng SARS under control? Yes, SARS is not superin
fectious. SARS is thought to be transmitted
most readily by respiratory
droplets, contact less than 3 ft. SARS is
spread on respiratory droplets, thus masks help
limit the spread. Temperature screeninghow it
was effective? It allowed people to feel that it
was ok to stay home. Is SARS here to stay?
A patient at the Singapore General Hospital
tested positive for the SARS -9/8/03. SARS posi
tive serum samples from 2001 In Feb 2004, 4 lab
workers in Beijing got SARS and spread it to 7
people, 1 died
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Ebola Virus
Negative strand RNA virus -Filoviridae family
First described in 1976 with 318 cases in Yambuk
u, Zaire and 284 cases in Nazara, Sudan Chara
cterized by high case-mortality rates
53 in Sudan and 88 in Zaire
Then really nothing until 1994 isolated from d
ead chimpanzees from the Ivory Coast
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1995 Ebola Outbreak
In Kikwit, Zaire -296 deaths 79 mortality rate
Health care workers were key to the spread of Eb
ola in Kikwit due to the poor conditions in the
hospital 1/3 of deaths were health care worke
rs It took 3-4 months before anyone in the deve
loped world took notice
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Other African Outbreaks
January 1996 there was 37 cases and 21 deaths in
Makokou, Gabon -most had butchered and eaten
dead chimpanzees October 1996 again in Makokou
, 24 cases with 17 deaths -index case was a hunt
er In 2004, Congo's Odzala National Park, many
of the parks 30,000 western lowland gorillas w
ere infected In 2007, DRC had 249 cases with 18
3 deaths, 73 mortality Nothing definite is kno
wn about the natural reservoir of the Ebola
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Can We Prevent Outbreaks of Ebola Virus ?
Has the Ebola virus changed or are the conditions
for the people different? Proper medical con
ditions would help tremendously
Not super contagious person-person? (e.g. people
on crowded trains have exposed many, but with
no or very little transmission Conditions in
Kikwit are worse now than in 1995
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Should we be Concerned about Ebola Virus?
Is the risk to Africa even compare to other
disease problems such as malaria and HIV? Wh
ere does Ebola come from? Is there a risk to pe
ople in North America and Europe?
If the time and place of such outbreaks is not p
redictable, should we just wait and react after
the fact?