October 21, 2009

This update provides new information about vaccination and treatment of HIV-infected adults and adolescents affected by 2009 H1N1 influenza.

Background

HIV-infected adults and adolescents, especially persons with low CD4 cell counts or AIDS, can experience more severe complications of seasonal influenza. Among patients hospitalized with confirmed 2009 influenza A (H1N1) infections in the United States, the prevalence of certain underlying conditions, including immunosuppressing conditions, has been higher than in the general population suggesting HIV-infected adults and adolescents also might be at higher risk for complications related to infection with 2009 influenza H1N1.

Clinical presentation

HIV-infected adults and adolescents with 2009 H1N1 influenza virus infection would be expected to present with typical acute respiratory illness (e.g., cough, sore throat, rhinorrhea) and fever or feverishness, headache, and muscle aches. Vomiting and diarrhea have been reported more often with 2009 H1N1 influenza virus infection than with seasonal influenza. As with seasonal influenza, some patients with 2009 H1N1 influenza will present without fever. Clinical judgment and local surveillance data on circulating influenza viruses and other respiratory pathogens are important in considering the differential diagnosis of patients presenting with influenza-like illness. For some HIV-infected persons, especially persons with low CD4 cell counts, illness might progress rapidly, and might be complicated by secondary bacterial infections including pneumonia.

Most HIV-infected persons with clinical illness consistent with uncomplicated influenza who reside in an area where influenza viruses are circulating do not require diagnostic influenza testing for clinical management. When a decision is made to use antiviral treatment for influenza, treatment should be initiated as soon as possible without waiting for influenza test results. Antiviral treatment is most effective when administered as early as possible in the course of illness. Patients who should be considered for influenza diagnostic testing include:

- Hospitalized HIV-infected persons with suspected influenza

- HIV-infected persons for whom a diagnosis of influenza will inform decisions regarding clinical care, infection control, or management of close contacts.

Clinicians should be aware that the sensitivities of rapid influenza diagnostic tests (RIDTs) and direct immunofluorescence assays (DFAs) are lower than real-time reverse transcriptase polymerase chain reaction (rRT-PCR) tests and viral culture. A negative RIDT or DFA result does not rule out influenza virus infection. Laboratory tests to diagnose 2009 H1N1 influenza, such as rRT-PCR, should be prioritized for hospitalized patients and severely immunocompromised persons with suspected influenza where RIDT or DFA testing is negative or to determine influenza A virus subtype in patients who have died from suspected or confirmed influenza A virus infection. Detailed recommendations on influenza diagnostic tests are available online.

Persons with HIV infection should remain vigilant for the signs and symptoms of influenza, as outlined above. Persons with HIV infection who are concerned that they might be experiencing signs or symptoms of influenza infection, or who are concerned they might have been exposed to a person with influenza illness, should consult their healthcare provider to assess the need for evaluation.

Treatment and chemoprophylaxis

Currently circulating 2009 H1N1 influenza viruses are sensitive to the neuraminidase inhibitor antiviral medications oseltamivir (Tamiflu) and zanamivir (Relenza), but are resistant to the adamantane antiviral medications, amantadine and rimantadine. Early empiric treatment with oseltamivir or zanamivir should be considered for HIV-infected adults and adolescents with suspected or confirmed influenza. Antiviral chemoprophylaxis can be considered for HIV-infected adults and adolescents who have had close contact with someone likely to have been infected with influenza. However, early treatment is an emphasized alternative to chemoprophylaxis after a suspected exposure. HIV-infected adults and adolescents who are household or close contacts of persons with confirmed or suspected influenza can be counseled about the early signs and symptoms of influenza, and advised to immediately contact their healthcare provider for evaluation and possible early treatment if clinical signs or symptoms develop. Early recognition of illness and treatment when indicated is preferred to chemoprophylaxis for vaccinated persons after a suspected exposure.

These recommendations for treatment and chemoprophylaxis are the same ones used for others who are at higher risk of complications from influenza. As is recommended for other persons who are treated, antiviral treatment with zanamivir or oseltamivir should be initiated as soon as possible after the onset of influenza symptoms, with benefits expected to be greatest if started within 48 hours of onset based on data from studies of seasonal influenza. However, some data from studies on seasonal influenza indicate benefit for hospitalized patients even if treatment is started more than 48 hours after onset. Health care providers should initiate empiric antiviral treatment as soon as possible. Waiting for laboratory confirmation of influenza to begin treatment with antiviral drugs is not necessary. Patients with a negative rapid influenza diagnostic test should be considered for treatment if clinically indicated because a negative rapid influenza test result does not rule out influenza virus infection.

Oseltamivir and zanamivir treatment and chemoprophylaxis regimens recommended for adults, including adults with HIV-infection, are the same as those recommended for adults who have seasonal influenza. Recommended duration of treatment is five days. Recommended duration of prophylaxis is 10 days after last exposure. Clinicians should monitor treated patients closely and consider the need to extend therapy based on the course of illness. Recommendations for use of influenza antivirals for HIV-infected adults and adolescents might change as additional data on the benefits and risks of antiviral therapy in such persons become available.

No adverse effects have been reported among HIV-infected adults and adolescents who received oseltamivir or zanamivir. There are no known absolute contraindications for co-administration of oseltamivir or zanamivir with currently available antiretroviral medications. Healthcare providers should observe patients for possible adverse drug reactions to anti-influenza agents.

Vaccination

A monovalent vaccine for 2009 H1N1 flu has been developed and is now available. (see MMWR 58(RR10); 1-8)

Persons between the ages of 25 and 64 years old with health conditions associated with higher risk of medical complications from influenza, including HIV infection, are an initial target group for the 2009 H1N1 flu vaccine and should be vaccinated for the 2009 H1N1 flu.

Additional groups recommended to receive the 2009 H1N1 influenza vaccine regardless of their HIV status include:

- Pregnant women

- Household contacts and caregivers for children younger than 6 months of age

- Healthcare and emergency medical services personnel

- All people from 6 months through 24 years of age

Once the demand for vaccine among the priority groups has been met at the local level, programs and providers should first offer 2009 H1N1 influenza vaccine to all persons 25-64 years of age and then to persons age 65 years or older, including HIV-infected adults. Current studies indicate that the risk for infection with 2009 H1N1 influenza among persons age 65 or older is less than the risk for younger age groups. Although initial supplies of vaccine are limited, supplies are expected to increase sufficiently to vaccinate all persons not in initial target groups.

This year's vaccine formulation for seasonal strains of influenza is not expected to protect against 2009 H1N1 influenza; vaccination against seasonal influenza (found at http://www.cdc.gov) is therefore also recommended for all HIV-infected adults, and, in this case, regardless of age. HIV-infected persons should receive only the injectable inactivated form of either vaccine. Although, vaccines against both seasonal and 2009 H1N1 influenza are also available as a nasal spray, these formulations contain live attenuated virus and are not approved for administration to HIV-infected persons and should not be used for this population.

Other ways to reduce risk for HIV-infected adults and adolescents

The risk for 2009 H1N1 influenza might be reduced by taking steps to limit exposures to persons with respiratory infections. These actions include frequent hand washing and minimizing contact with other persons who might be ill with 2009 H1N1 flu. People at high risk should consider avoiding, when possible, crowded settings in communities where 2009 H1N1 flu is circulating. People at increased risk of severe complications from flu might consider using facemasks or respirators if they cannot avoid a crowded setting while 2009 H1N1 influenza is circulating in their community. Facemasks and respirators should be used along with other preventive measures, such as avoiding close contact with ill persons and maintaining good hand hygiene. Interim guidance regarding recommendations for facemask and respirator use is available. This guidance will be updated as more information becomes available, including information on the risk of 2009 H1N1 flu-related complications among HIV-infected adults and adolescents.

Patients should be reminded of the importance of maintaining their health as a means of reducing their risk of infection with influenza and improving their immune system's ability to fight an infection should it occur. In particular, patients who are currently taking antiretrovirals or antimicrobial prophylaxis against opportunistic infections should be reminded of the importance of adhering to their prescribed treatment.