Modalità di trasmissione e diffusione del virus negli adulti - Massimo Galli DIBIC L.Sacco, UNIMI Malattie Infettive III, ASST FBF/Sacco Milano
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Modalità di trasmissione e diffusione
del virus negli adulti
Massimo Galli
DIBIC L.Sacco, UNIMI
Malattie Infettive III, ASST FBF/Sacco Milano
4458
Casi di COVID-19 diagnosticati in Italia per
comune di domicilio/residenza
14 - 27 settembre 2020
All but one of the
newly-characterized
genomes belonged to
the lineage B.1, the
most frequently
identified in European
countries, including
Italy. Only a single
sequence was found to
belong to lineage B.
tMRCA estimation confirmed the probable origin of the epidemic
between the end of January and the beginning of February with
a rapid increase in the number of infections between the end of
February and mid-March. Since early February, an effective
reproduction number (Re) greater than 1 was estimated, which then
increased reaching the peak of 2.3 in early March, confirming the
circulation of the virus before the first COVID-19 cases were
documented.
Viruses 2020, 12, 798;doi:10.3390/v12080798
Human
SARS-CoV ACE2
spike protein
SARS-CoV
spike RBD
ACE: angiotensin-converting enzyme 2
Transmission of SARS-CoV-2
• Respiratory transmission is the dominant mode of transmission.
• Vertical transmission occurs rarely; transplacental transmission
has been documented.
• Cats and ferrets can be infected and transmit to each other, but
there are no reported cases to date of transmission to humans;
minks transmit to each other and to humans.
• Direct contact and fomite transmission are presumed but are
likely only an unusual mode of transmission.
• Although live virus has been isolated from saliva and stool and
viral RNA has been isolated from semen and blood donations,
there are no reported cases of SARSCoV-2 transmission via fecal–
oral, sexual, or bloodborne routes.
• To date, there is 1 cluster of possible fecal–respiratory
transmission.
Meyerowitz et al. Ann Intern Med. doi:10.7326/M20-5008
In a closed, stagnant air environment, droplets disappear from the window of view with time constants in the range of 8 to 14 min, which corresponds to droplet nuclei of ca. 4 μm diameter, or 12- to 21-μm droplets prior to dehydration. These observations confirm that there is a substantial probability that normal speaking causes airborne virus transmission in confined environments. Light scattering observation of airborne speech droplet nuclei, generated by a 25-s burst of repeatedly speaking the phrase “stay healthy” in a loud voice.
The serial interval of COVID-19 is defined as the time duration between a primary case-patient
(infector) having symptom onset and a secondary case-patient (infectee) having symptom onset.
We estimate a mean serial interval for COVID-19
of 3.96 (95% CI 3.53–4.39) days, with an SD of
4.75 (95% CI 4.46–5.07) days, which is
considerably lower than reported mean serial
intervals of 8.4 days for SARS to 14.6 days for
MERS.
Fifty-nine of the 468 reports indicate that the
infectee had symptoms earlier than the infector.
Thus, presymptomatic transmission might be
occurring.
Gray bars indicate the number of infection events
with specified serial interval, and blue lines indicate
fitted normal distributions. Negative serial intervals
(left of the vertical dotted lines) suggest the
possibility of COVID-19 transmission from
asymptomatic or mildly symptomatic case-patients.
Zhanwei Du. Emerg Infect Dis. 2020 Jun
Asymptomatic infection may
be associated with
subclinical lung
abnormalities, as detected
by computed tomography.N Engl J Med 2020382; 22: 2158-60
Attack rates: < 20 years: 5.2%
20 – 59 years: 14.8%
> 60 years: 18.4%
Compared with the oldest age group (≥60 years; OR 1.00), the risk of household infection was:
• lower in the youngest age group (Few infectious subjects might account for
the majority secondary casesSeroprevalence of
SARS-CoV-2 IgG
significantly varies
with age:
results from a mass
population screening
Pagani et al, J. Infection 2020Un esempio di contagio da SARS-CoV-2: Ristorante in Cina
CASO INDICE
Asintomatico,
malattia
conclamatasi in
serata
CASI SECONDARI
Lu J, et al. Emerg Infect Dis. 2020
Jul;26(7):1628-31Dynamics of
neutralizing
antibody titers in
the months after
SARS-CoV-2
infection
• Neutralizing antibody
titers declined an average
of about four-fold from
one to four months post
symptom onset.
• This decline was
accompanied by a decline
in total antibodies capable
of binding the viral spike
or its receptor-binding
domain.
• Data are consistent with
the expected early
immune response to viral
infection, where an initial
peak in antibody levels is
followed by a decline to a
lower plateau
Crawford KHD,et al.J Infect Dis. 2020 Sep 30:jiaa618Symptomatic SARS-CoV-2 reinfection
by a phylogenetically distinct strain
• In March 2020, a 51-year-old women presented to the general
practitioner symptoms of headache, fever, myalgia, coughing, chest
pain and dyspnea. She also mentioned anosmia and a change in tasteIn
March 2020, a 51-year-old women presented to the general
practitioner symptoms
• Oxygen saturation by capillary oximeter was 94%. Hospitalisation was
not deemed necessary at the time and the patient was asked to
selfquarantine for 2 weeks. Because of persisting symptoms of
tiredness, muscle pains and dyspnoea, she stayed at home for 5 weeks
before returning to work.
• Three months after initial onset of symptoms, she experienced a
relapse of symptoms with headache, cough and fatigue. Rhinitis was
also present. There was no travel history.
• The patient told the general practitioner that the symptoms felt similar
to the first episode in March, although milder. The nasopharyngeal
swab was again positive for SARS-CoV-2,suggesting a reinfection
• Full-length genome sequencing with ONT MinION revealed that the
initial infectionwas caused by a lineage B.1.1 SARS-CoV-2 virus and
the relapsing infection by a lineage A
Van Elslande et al. CID 2020 5 sept.Nature • The determinants of disease severity seemed to stem mostly from host factors such as age, lymphocytopenia, and its associated cytokine storm, whereas viral genetic variation did not significantly affects the outcomes
Lethality rate by age group Age deceased % lethality
Distribuzione di casi, decessi e
letalità negli operatori sanitari
ISS 29/09/2020A lying ranking
Percentuale di casi di COVID-19 diagnosticati in
Italia per stato clinico al momento della diagnosi e
settimana di diagnosi
ISS 29/09/2020Quali occasioni non possiamo
perdere?
• L’epidemia ha posto l’accento sulle carenze della
organizzazione ospedaliera ed ancor di più su
quelle della medicina territoriale.
• È pertanto evidente la necessità di un
ripensamento profondo su strutture e
investimenti.
• La rete infettivologica è più che mai necessaria
• In cinese, la parola crisi è composta di due
caratteri. Uno rappresenta il pericolo e l'altro
l'opportunità.Grazie per l’attenzione
Tracciatura e gestione dei contatti
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focolaio spentoGenome characterization of 2019-nCoV
Rhinolophus affinis
Zhou et al Nature 2020You can also read
