Pregnancy is a risk factor for increased illness and death from influenza. At especially high risk during the influenza season are pregnant women with underlying medical conditions  such as asthma [2]. The CDC recommends pregnant women with confirmed, probable, or suspected novel influenza A (H1N1) virus infection should receive antiviral treatment for 5 days. Oseltamivir is the preferred treatment [4].

Incubation Period

The incubation period is most likely 1 to 4 days but could range from 1 to 7 days. The duration of shedding with novel influenza A (h1N1) virus is unknown. However, infected persons should be assumed to be contagious for up to 7 days from illness onset. Some infected persons such as young infants or immunosuppressed persons  might potentially be contagious for longer periods [3]. All respiratory secretions and bodily fluids (diarrheal stool) of novel influenza A (H1N1) cases should be considered potentially infectious. However, breast milk is not thought to be a potential source of influenza virus infections [10].
 

• Fever (temperature of 100°F [37.8°C] or greater)
• Cough and/or Sore throat
• Runny or stuffy nose
• Body aches
• Headache
• Chills
• Fatigue

Some people may also have

• Nausea
•  vomiting and/or diarrhea

Most people with uncomplicated influenza recover in 1-2 weeks

Who to Test

"Not all people with suspected novel influenza (H1N1) infection need to have the diagnosis confirmed, especially if the person resides in an affected area or if the illness is mild. Recommendations on who to test may differ by state or community."[3].

Priority for testing should be given to patients who require hospitalization or patients  at high-risk for severe disease such as:"

• Children younger than 5 years old. The risk for severe complications from seasonal influenza is highest among children younger than 2 years old.
• Adults 65 years of age and older.
• Persons with the following conditions:
  • Chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, hematological (including sickle cell disease), neurologic, neuromuscular, or metabolic disorders (including diabetes mellitus);
  • Immunosuppression, including that caused by medications or by HIV;
  • Pregnant women;
  • Persons younger than 19 years of age who are receiving long-term aspirin therapy;
  • Residents of nursing homes and other chronic-care facilities."[3]

As soon as possible after illness onset collect nasopharyngeal swab, nasal aspirate or a combined nasopharyngeal swab with oropharyngeal swab using swabs with a synthetic tip (e.g. polyester or Dacron®) and an aluminum or plastic shaft. Specimens should be placed into sterile viral transport media (VTM) and immediately placed on ice or cold packs or at 4°C (refrigerator) for transport to the laboratory.

"Available rapid tests can distinguish between influenza A and B viruses. However, these tests may not be sensitive enough to detect the influenza A (H1N1) virus. A negative result does not exclude a diagnosis of swine influenza A. A positive result may be helpful, but does not distinguish between seasonal and swine influenza viruses. Therefore, if a patient tests negative for influenza by rapid antigen testing, specimens should be sent for further characterization (including PCR and subtyping) to the local public health laboratories or VRDL" [5].

ANY SUSPECT OR LABORATORY-CONFIRMED CASES SHOULD BE REPORTED TO THE LOCAL HEALTH DEPARTMENT AND THE CALIFORNIA DEPARTMENT OF PUBLIC HEALTH IMMEDIATELY [5]

Suspected Novel Influenza A (H1N1) Infection [6]

A suspected case of novel influenza A (H1N1) virus infection in California is any patient with an acute febrile respiratory illness*, due to the transmission of novel influenza A (H1N1) virus throughout the state and the presentation of patients with this illness.

*Acute febrile respiratory illness is a measured temperature of ≥37.8°C (100°F) plus recent onset of at least one of the following: runny nose or nasal congestion, sore throat, or cough.

Probable Novel Influenza A (H1N1) Infection [6]

A probable case of novel influenza A (H1N1) virus infection is defined as a person with an influenza-like-illness who is positive for influenza A by rapid test, but negative for human H1 and H3 by influenza reverse-transcription polymerase chain reaction (RT-PCR)

Confirmed Novel Influenza A (H1N1) Infection [6]

A confirmed case of novel influenza A (H1N1) virus infection is defined as a person with an influenza-like illness with laboratory confirmed novel influenza A (H1N1) virus infection by real-time RT-PCR and or viral culture.

"Pregnant women with confirmed, probable, or suspected novel influenza A (H1N1) virus infection should receive antiviral treatment for 5 days. Oseltamivir is the preferred treatment for pregnant women, and the drug regimen should be initiated within 48 hours of symptom onset, if possible. Pregnant women who are in close contact with a person with confirmed, probable, or suspected novel influenza A (H1N1) infection should receive a 10-day course of chemoprophylaxis with zanamivir or oseltamivir." [4, 7]

Treatment is also recommended for:

• All hospitalized patients with confirmed, probable or suspected novel influenza (H1N1).
• Patients who are at higher risk for seasonal influenza complications as noted above.

Antiviral drugs work best if started soon after getting sick (within 2 days of symptoms). Mothers who are breastfeeding can continue to nurse their babies while being treated for the flu [8,9].

Oseltamivir (Tamiflu ®)

Adults

Treatment 

75-mg capsule orally twice per day for 5 days

Chemoprophylaxis

75-mg capsule once per day for 10 days after the last close contact (within 6 feet) with a person who is a confirmed, probable or suspected case of novel influenza A (H1N1) virus infection during the infectious period of the case.

Zanamivir (Relenza ®)

Adults

Treatment

Two 5-mg inhalations (10 mg total) twice per day

Chemoprophylaxis

Two 5-mg inhalations (10 mg total) once per day for 10 days after the last close contact  (within 6 feet) with a person who is a confirmed, probable or suspected case of novel influenza A (H1N1) virus infection during the infectious period of the case.

• Self-isolate in their home for 7 days or until their temperature has subsided,
  whichever is longer.
  
• Seek medical care for severe respiratory symptoms such as difficulty breathing or for dehydration from vomiting and/or diarrhea. They may also need to seek early medical attention if they have a chronic health condition that puts them at risk for the complications of influenza.
• If the patient must go into the community (e.g., for medical care), they should be instructed to wear a mask over their nose and mouth when within six feet of other persons."

Obstetric Settings [10]

The Centers for Disease Control recommends:

In obstetric settings when a pregnant woman has confirmed, probable or suspected novel H1N1 flu

• Isolate the ill mother from healthy pregnant women .
• Place a surgical mask on the ill mother during labor and delivery, if tolerable, in order to decrease exposure of the newborn, healthcare personnel, and other labor and delivery patients to potentially infectious respiratory secretions
• Place the ill mother in isolation after delivery
• The mother should avoid close contact with her infant until she has received antiviral medications for 48 hours, her fever has fully resolved, and she can control coughs and secretions.
  • In the meantime, the newborn should be cared for in a separate room by another person who is well, and the mother should be encouraged and assisted to express her milk.
• After 48 hours of antiviral medications, her fever has fully resolved, and she can control coughs and secretions  the mother should be encouraged to wear a facemask, change to a clean gown or clothing, adhere to strict hand hygiene and cough etiquette when in contact with her infant, and begin breastfeeding (or if not able to breastfeed, bottle feeding).
• She should continue these protective measures, both in the hospital setting and at home, for at least 7 days after the onset of influenza symptoms

See Considerations Regarding Novel H1N1 Flu Virus in Obstetric Settings for full recommendations.

• What Pregnant Women Should Know About H1N1 (formerly called swine flu) Virus
• Considerations Regarding Novel H1N1 Flu Virus in Obstetric Settings
• H1N1 Flu (Swine Flu): Centers for Disease Control and Prevention
• Novel Influenza A (H1N1) Virus (Swine Flu). California Department of Public Health

REFERENCES

1. Novel H1N1 Flu Situation Update
http://www.cdc.gov/H1n1flu/update.htm Accessed 7-19-09

2.Rasmussen SA, Jamieson DJ, Bresee JS. Pandemic influenza and pregnant women. Emerg Infect Dis [serial on the Internet]. 2008 Jan [7-20-2009]. Available from http://www.cdc.gov/EID/content/14/1/95.htm Accessed 7-19-09

3.  http://www.cdc.gov/h1n1flu/specimencollection.htm Accessed 7-19-09

4. Novel influenza A (H1N1) virus infections in three pregnant women - United States, April-May 2009. MMWR Morb Mortal Wkly Rep. 2009 May 15;58(18):497-500. PMID: 19444154http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5818a3.htm Accessed 7-19-09

5. California Department of Public Health Viral and Rickettsial Disease Laboratory (VRDL) Swine Influenza A (H1N1) Surveillance http://www.cdph.ca.gov/PROGRAMS/VRDL/Pages/TestingforSwineInfluenzaA(H1N1).aspx
 Accessed 7-19-09

6. CALIFORNIA DEPARTMENT OF PUBLIC HEALTH NOVEL INFLUENZA A (H1N1) VIRUS (SWINE FLU)INFECTION CONTROL RECOMMENDATIONS IN AN OUTPATIENT SETTING May 19, 2009 http://www.cdph.ca.gov/HealthInfo/discond/Documents/CDPH-AFL-Update-Infection-Control-H1N1-Influenza-Outpatient-Settings.pdf Accessed 7-19-09

 7. Tanaka T, et al "Safety of neuraminidase inhibitors against novel influenza A (H1N1) in pregnant and breastfeeding women" CMAJ 2009; DOI:10.1503/cmaj.090866. Accessed 7-19-09

8. Interim Guidance on Antiviral Recommendations for Patients with Novel Influenza A (H1N1) Virus Infection and Their Close Contacts. http://www.cdc.gov/h1n1flu/recommendations.htm Accessed 7-19-09

9. What Pregnant Women Should Know About H1N1 (formerly called swine flu) Virus
http://www.cdc.gov/h1n1flu/guidance/pregnant.htm Accessed 7-19-09

10. Considerations Regarding Novel H1N1 Flu Virus in Obstetric Settings
http://www.cdc.gov/H1n1flu/update.htm Accessed 7-20-09

Created 7-19-2009
Updated:7-20-09