September 21, 2009
In March 2009 a new flu virus called H1N1 (also called swine flu) emerged in Mexico and quickly spread around the world. Now, as winter approaches, a time when flu infections are common, health authorities expect that H1N1 infections will surge in countries and regions in the northern hemisphere, including Canada, the United States, the European Union, Mexico and the Caribbean.
For many people, infection with the H1N1 virus causes mild-to-moderate flu symptoms that resolve in about a week. However, in a small proportion of people, infection with the H1N1 virus can cause serious complications that may require hospitalization. We are not yet certain about the factors that are responsible for these serious complications. However, based upon the best available evidence, people with weakened immune systems, including people with HIV, are expected to be at increased risk for complications arising from H1N1 infection.
In this CATIE News bulletin, we provide you with key information about H1N1, including tips on the prevention and treatment of H1N1 in adults with HIV.
Like other influenza viruses, the H1N1 virus does not affect everyone in the same way. As H1N1 is an emerging infection, there is very little information about its specific impact on people living with HIV. Based on current understanding, here are some of the factors that may increase vulnerability to H1N1-related complications for people living with HIV.
People whose immune systems have been weakened by HIV are at increased risk for complications from influenza and possibly the H1N1 virus. This includes people with low CD4+ counts. Because many people are not diagnosed with HIV until the late stages of infection, there is a hidden population of people in this category who don't know they are HIV positive and are at increased risk for complications arising from influenza and H1N1 infection.
HIV positive people who have high CD4+ counts may also be at increased risk, even if they are taking anti-HIV drugs. Several studies have found that despite the use of anti-HIV drugs, people with HIV are still at increased risk for complications arising from seasonal flu, such as bacterial chest infections.
Some people with HIV can have other conditions that can weaken the immune system and may make them more vulnerable to seasonal flu, including the following:
The conditions listed above may also increase the risk for complications from H1N1 infection.
Doctors in Canada, Mexico, the United States and elsewhere who have treated many people with H1N1 infection have found additional factors that appear to increase the risk of getting this infection:
Many experts recommend that HIV positive people be prioritized to receive the vaccine for H1N1 when it becomes available.
This virus is transmitted in the same way seasonal flu is spread. When an infected person coughs or sneezes, they release a spray of tiny droplets of muc us containing flu viruses. If these droplets are inhaled by a person in close proximity, that person can also become infected. If the droplets land on surfaces such as counters, desks, door handles or doorknobs, they can be picked up by touch. Another person who touches these surfaces and then his or her nose, mouth or eyes can become infected. Also, flu viruses can survive on the skin, so shaking hands with an infected person can transmit these viruses. Flu viruses can survive outside the body on surfaces for up to 24 hours.
Here are some measures to help protect you from H1N1. These measures have generally been recommended by the Public Health Agency of Canada, the U.S. Centers for Disease Control and Prevention (CDC) and the European Centres for Disease Control:
Several vaccines against H1N1 are being tested in different parts of the world. While we don't have any specific information on how effective these vaccines will be for HIV positive people, it is expected, based on years of experience with other flu vaccines, that they will be as safe and effective as they are in HIV negative people. Federal, provincial, territorial and municipal health authorities will be creating a strategy for vaccination throughout Canada. Stay informed and aware of when the vaccine will become available in your region (see the Resource section at the end of this bulletin for information on how to stay informed). When the H1N1 vaccine does become available, talk to your doctor or nurse about getting this vaccine.
Antiviral drugs such as oseltamivir or zanamivir can, in some circumstances, be used t o help prevent H1N1 infection in people who are exposed to this virus but do not have symptoms of the flu. Using medicines in this way is called PEPpost-exposure prophylaxis. If you have been in close contact with a person who has been diagnosed with H1N1, speak to your doctor or nurse about the possibility of getting antiviral drugs to help protect you from H1N1 infection.
Because the signs and symptoms of H1N1 infection are very similar to seasonal flu, only your doctor or nurse can help diagnose the cause of your symptoms. Here are some of the symptoms associated with H1N1 infection:
In some cases diarrhea and vomiting may also occur.
In extreme cases, the following signs/symptoms may also develop. If you experience the symptoms below, immediately contact your health care provider or dial 911:
Because the signs and symptoms of H1N1 infection are very similar to those of seasonal flu, only your doctor or nurse can help diagnose the cause of your symptoms. If you experience flu-like symptoms, contact your doctor or nurse for advice. They will help decide what steps should be taken, such as whether you need antiviral medicines.
To avoid infecting other people with H1N1, stay at home as directed by your doctor or nurse.
If you experience severe flu-like symptoms, do not assume that the cause is H1N1. There are many other serious infections and conditions that can cause similar symptoms. Always seek medical advice for managing severe symptoms.
For many people with H1N1 infection, health care providers will recommend home care and careful monitoring of symptoms. For this reason, it is important to be prepared to take care of yourself and others at home.
If your doctor or nurse has told you or someone in your household to stay at home because of H1N1 infection, here are some things to do to help manage illness and prevent the spread of infection:
When your symptoms have cleared, talk to your doctor or nurse about returning to work or volunteer activities. In the days after your symptoms have cleared, your body will produce gradually decreasing amounts of H1N1. So once you are back at work or volunteering, it is important to keep washing your hands and practice safer coughing and sneezing behaviour so that you do not infect other people.
There are two antiviral drugs available on prescription that can be used to treat H1N1:
These are the only medicines approved by authorities for the treatment of H1N1. They are most effective if used within 48 hours of the appearance of flu symptoms. Because the symptoms of seasonal flu are very similar to symptoms of H1N1, only your doctor or nurse can help diagnose the cause of your symptoms.
Usually treatment with these drugs lasts for five days. However, in cases of severe illness, particularly in people with weakened immune systems who have been hospitalized, some infectious disease specialists may prescribe longer courses or higher doses of treatment.
Here are some helpful tips to bear in mind when taking these antiviral drugs:
More information about the treatment of H1N1 can be found here.
Oseltamivir and zanamivir have not been tested in clinical trials in pregnant women. However, doctors have had to treat pregnant women with these drugs so there is some information about their safety. The U.S. CDC20has noted that pregnant women who have H1N1 can be given these drugs. Zanamivir tends to concentrate in the lungs while oseltamivir can reach all tissues in the body. The CDC therefore recommends the use of oseltamivir in pregnant women with H1N1.
Some people who used this drug reported such problems as nausea, vomiting and diarrhea. Taking oseltamivir with food may reduce nausea or vomiting. There are reports that Japanese children who have taken oseltamivir have developed neuro-psychiatric problems. However, this has not been generally reported in Japanese or non-Japanese adults.
This drug can irritate the lungs of people who have pre-existing lung conditions such as asthma. The U.S. CDC recommends that people with pre-existing lung conditions use oseltamivir instead of zanamivir. In some zanamivir users, diarrhea, nausea, headache and dizziness have occurred.
For more information about less common side effects of oseltamivir or zanamivir, speak to your pharmacist.
As H1N1 is an emerging infection, there is little information on interactions between anti-flu drugs and medicines used for the treatment of HIV infection. So far, no serious or life-threatening interactions between drugs used for the treatment of H1N1 and drugs used for the treatment of HIV have been documented.
Stay aware and informed by listening to or reading the news about H1N1 in your region. Additionally, as the winter outbreak of H1N1 unfolds, public health agencies will be posting updates. Here are some sites with reliable information:
Public Health Agency of Canada
British Columbia Centres for Disease Control
Ontario Ministry of Health and Long-term Care
Quebec Ministry of Health
U.S. Centers for Disease Control and Prevention
French Ministry of Health
World Health Organization
We thank Curtis Cooper, MD, from the Ottawa Hospital, for helpful discussion, research assistance and expert review.