Distributed via the CDC Health Alert Network
June 7, 2013, 14:00 ET 02:00 PM ET
CDCHAN-00347
This health advisory provides an
update
on the avian influenza A (H7N9) virus [H7N9] situation and includes new
recommendations on who should be tested for H7N9 in the United States.
This document replaces guidance published on April 5, 2013, in CDC
Health Advisory 344 “Human Infections with Novel Influenza A (H7N9)
Viruses,” found at
http://emergency.cdc.gov/HAN/han00344.asp.
The updated guidance reflects the most current epidemiology of H7N9
cases, which indicates that almost all H7N9 human infections have
resulted in severe respiratory illness; H7N9 has been found rarely
among those with milder disease. For that reason, CDC is changing its
recommendations for H7N9 testing:
The primary changes from
previous guidance are (i) a new recommendation to test only patients
with an appropriate exposure history and severe respiratory illness
requiring hospitalization and (ii) a request that only confirmed and
probable cases of human infection with H7N9 be reported to CDC.
In the previous guidance issued on April 5, CDC recommended that all
persons with relevant exposure history and illness compatible with
influenza, regardless of severity be tested. CDC will continue to
update these recommendations as more information becomes available. The
current guidance is consistent with interim surveillance
recommendations by the World Health Organization for H7N9 found at
http://www.who.int/influenza/human_animal_interface/influenza_h7n9/InterimSurveillanceRecH7N9_10May13.pdf
Summary and Background
As of June 3, 2013, Chinese public health officials have reported
>130 cases of human infection with H7N9 from 10 provinces and
municipalities in mainland China and Taiwan [1, 2]. Most patients were
hospitalized with severe respiratory illness and reported poultry
contact prior to illness onset [2, 3]. Preliminary results from
influenza-like illness surveillance suggest that H7N9 has not caused
widespread mild illness in China [4].
Although several clusters of human infection with H7N9 have been identified in China,
sustained
person-to-person transmission of the virus has not been demonstrated.
At this time, no cases of human infection with H7N9 have been detected
in the United States, despite testing of >60 persons with respiratory illness who reported recent travel to China.
Clinicians should consider the possibility of H7N9 infection in
persons presenting with respiratory illness requiring hospitalization
and an appropriate travel or exposure history. Influenza diagnostic
testing in patients with severe respiratory illness for whom an
etiology has not been confirmed may identify human cases of H7N9.
Confirmed and
probable cases of human infection with H7N9 in the United States should be reported to CDC within 24 hours of initial detection. See
http://www.cdc.gov/flu/avianflu/h7n9/case-definitions.htm.
However, state health departments are encouraged to investigate all
potential cases of H7N9 infection as described below in order to
determine case status.
Interim Recommendations for Clinicians and State and Local Health Departments
CDC recommends the following testing practices based on the current epidemiology of H7N9 cases.
Case Investigation and Testing
- Patients who meet both the clinical and exposure criteria
described below should be considered for H7N9 testing by
reverse-transcription polymerase chain reaction (RT-PCR) methods.
Decisions on diagnostic testing for influenza using RT-PCR should be
made using available clinical and epidemiologic information, and
additional persons in whom clinicians suspect H7N9 infection should also
be tested.
Clinical Illness Criteria
i. Patients with new-onset severe acute respiratory infection requiring hospitalization
(i.e., illness of suspected infectious etiology that is severe enough
to require inpatient medical care in the judgment of the treating
clinician).
AND
ii. Patients for whom no alternative infectious etiology is identified.
Exposure Criteria
i. Patients with recent travel (within 10 days of illness onset) to
areas where human cases of H7N9 have become infected or to areas where
avian influenza A (H7N9) viruses are known to be circulating in animals
1.
OR
ii. Patients who have had recent close contact (within 10 days of
illness onset) with confirmed cases of human infection with H7N92.
Close contact may be regarded as coming within about 6 feet (2 meters)
of a confirmed case while the case was ill (beginning 1 day prior to
illness onset and continuing until resolution of illness). Close
contact includes healthcare personnel providing care for a confirmed
case, family members of a confirmed case, persons who lived with or
stayed overnight with a confirmed case, and others who have had similar
close physical contact.
- If infection with H7N9 is suspected based on current clinical and
epidemiological screening criteria recommended by public health
authorities, respiratory specimens should be collected with appropriate
infection control precautions for novel virulent influenza viruses and
sent to the state or local health department for testing. Clinicians
should obtain a respiratory specimen from these patients, place the
swab or aspirate in viral transport medium, and contact their state or
local health department to arrange transport and request a timely
diagnosis at a state public health laboratory or CDC. Viral culture should not be attempted in these cases. For additional guidance on diagnostic testing of patients under investigation for H7N9 infection, please see http://www.cdc.gov/flu/avianflu/h7n9/specimen-collection.htm.
- Commercially available rapid influenza diagnostic tests (RIDTs)
may not detect H7N9 viruses in respiratory specimens. Therefore, a
negative rapid influenza diagnostic test result does not exclude
infection with H7N9. In addition, a positive test result for influenza A
cannot confirm avian influenza virus infection because these tests
cannot distinguish between influenza A virus subtypes (they do not
differentiate between human influenza A viruses and novel3
influenza viruses). Therefore, when RIDTs are positive for influenza A
and there is concern for novel influenza A virus infection, respiratory
specimens should be collected and sent for RT-PCR testing at a state
public health laboratory. Clinical treatment decisions should not be
made on the basis of a negative rapid influenza diagnostic test result
since the test has only moderate sensitivity (http://www.cdc.gov/flu/professionals/diagnosis/clinician_guidance_ridt.htm).
Infection Control
Clinicians should be aware of appropriate infection control
guidelines for patients under investigation for infection with novel
influenza A viruses. For guidance on infection control precautions for
H7N9 see
http://www.cdc.gov/flu/avianflu/h7n9-infection-control.htm.
Treatment
For guidance on treatment of patients under investigation for H7N9
with antiviral medications, or for guidance on antiviral
chemoprophylaxis of exposed contacts, see
http://www.cdc.gov/flu/avianflu/h7n9-antiviral-treatment.htm.
For More Information
End Notes:
1 As of June 3, 2013, China was the only country where H7N9
viruses were known to be circulating in animals or where human cases
have become infected. Patients with direct or close contact with wild
birds or poultry, or animal settings, such as live poultry markets
while traveling in these areas should be strongly considered for H7N9
testing. For more information on countries affected, please see the CDC
avian influenza A (H7N9) information page at
http://www.cdc.gov/flu/avianflu/h7n9-virus.htm.
2 Contact investigation protocols for confirmed cases may
supersede the recommendations described here; testing of close
contacts with
any level of respiratory illness may be pursued, if in the judgment of the investigators, this is warranted.
3 Influenza viruses that do not typically infect humans
are called "novel" influenza viruses; this includes influenza viruses
that typically infect birds and swine.
References:
1. Centers for Disease Control and Prevention. Emergence of Avian
Influenza A(H7N9) Virus Causing Severe Human Illness - China,
February-April 2013. MMWR
2013; 62(18): 366-71.
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6218a6.htm?s_cid=mm6218a6_w
2. Li Q, Zhou L, Zhou M, et al. Preliminary Report: Epidemiology of the Avian Influenza A (H7N9) Outbreak in China.
N Engl J Med. 2013 Apr 24. [Epub ahead of print].
http://www.ncbi.nlm.nih.gov/pubmed/?term=Epidemiology+of+the+Avian+Influenza+A+(H7N9)+Outbreak+in+Chin
3. Lee SS, Wong NS, Leung CC. Exposure to avian influenza H7N9 in
farms and wet markets. Lancet May 25;381(9880):1815. doi:
10.1016/S0140-6736(13)60949-6. Epub
2013 May 10.
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(13)60949-6/fulltext?rss=yes
4. Xu C, Havers F, Wang L, Chen T, Shi J, Wang D. Monitoring avian
influenza A(H7N9) virus through national influenza-like illness
surveillance, China. Emerging Infectious Diseases [Internet],
2013 Jul [
June 3, 2013].
http://dx.doi.org/10.3201/eid1908.130662.
http://emergency.cdc.gov/HAN/han00347.asp
