What can I do to protect myself from catching influenza A(H1N1)?
The main route of transmission of the new influenza A(H1N1) virus seems to be similar to seasonal influenza, via droplets that are expelled by speaking, sneezing or coughing. You can prevent getting infected by avoiding close contact with people who show influenza-like symptoms (trying to maintain a distance of about 1 metre if possible) and taking the following measures:
avoid touching your mouth and nose;
clean hands thoroughly with soap and water, or cleanse them with an alcohol-based hand rub on a regular basis (especially if touching the mouth and nose, or surfaces that are potentially contaminated);
avoid close contact with people who might be ill;
reduce the time spent in crowded settings if possible;
improve airflow in your living space by opening windows;
practise good health habits including adequate sleep, eating nutritious food, and keeping physically active.
What about using a mask? What does WHO recommend?
If you are not sick you do not have to wear a mask.
If you are caring for a sick person, you can wear a mask when you are in close contact with the ill person and dispose of it immediately after contact, and cleanse your hands thoroughly afterwards.
If you are sick and must travel or be around others, cover your mouth and nose.
Using a mask correctly in all situations is essential. Incorrect use actually increases the chance of spreading infection.
How do I know if I have influenza A(H1N1)?
You will not be able to tell the difference between seasonal flu and influenza A(H1N1) without medical help. Typical symptoms to watch for are similar to seasonal viruses and include fever, cough, headache, body aches, sore throat and runny nose. Only your medical practitioner and local health authority can confirm a case of influenza A(H1N1).
What should I do if I think I have the illness?
If you feel unwell, have high fever, cough or sore throat:
stay at home and keep away from work, school or crowds;
rest and take plenty of fluids;
cover your nose and mouth when coughing and sneezing and, if using tissues, make sure you dispose of them carefully. Clean your hands immediately after with soap and water or cleanse them with an alcohol-based hand rub;
if you do not have a tissue close by when you cough or sneeze, cover your mouth as much as possible with the crook of your elbow;
use a mask to help you contain the spread of droplets when you are around others, but be sure to do so correctly;
inform family and friends about your illness and try to avoid contact with other people;
If possible, contact a health professional before traveling to a health facility to discuss whether a medical examination is necessary.
Should I take an antiviral now just in case I catch the new virus?
No. You should only take an antiviral, such as oseltamivir or zanamivir, if your health care provider advises you to do so. Individuals should not buy medicines to prevent or fight this new influenza without a prescription, and they should exercise caution in buying antivirals over the Internet.
What about breastfeeding? Should I stop if I am ill?
No, not unless your health care provider advises it. Studies on other influenza infections show that breastfeeding is most likely protective for babies - it passes on helpful maternal immunities and lowers the risk of respiratory disease. Breastfeeding provides the best overall nutrition for babies and increases their defense factors to fight illness.
What should I do if I need medical attention?
If possible, contact your health care provider before traveling to a health facility, and report your symptoms. Explain why you think you have influenza A (H1N1) (e.g. if you have recently traveled to a country where there is an outbreak in people). Follow the advice given to you.
If you cannot contact your health care provider before traveling to a health facility, tell a health care worker of your suspicion of infection immediately after arrival at the clinic or hospital.
Cover your nose and mouth during travel.
Should I go to work if I have the flu but am feeling OK?
No. Whether you have influenza A(H1N1) or a seasonal influenza, you should stay home and away from work through the duration of your symptoms. This is a precaution that can protect your work colleagues and others.
Can I travel?
If you are feeling unwell or have symptoms of influenza, you should not travel. If you have any doubts about your health, you should check with your health care provider.
Are some people more at risk?
More study is needed to determine if some populations (i.e. younger or older people, or people with other medical conditions) could be affected by the outbreak, of if they are at higher risk for severe illness. WHO recommends that everyone take precautions to prevent the spread of infection.
Are there any special recommendations for pregnant women?
Yes, they are vulnerable. Like everyone, they should take all the necessary precautions.
The current WHO phase of pandemic alert is 6.
In nature, influenza viruses circulate continuously among animals, especially birds. Even though such viruses might theoretically develop into pandemic viruses, in Phase 1 no viruses circulating among animals have been reported to cause infections in humans.
In Phase 2 an animal influenza virus circulating among domesticated or wild animals is known to have caused infection in humans, and is therefore considered a potential pandemic threat.
In Phase 3, an animal or human-animal influenza reassortant virus has caused sporadic cases or small clusters of disease in people, but has not resulted in human-to-human transmission sufficient to sustain community-level outbreaks. Limited human-to-human transmission may occur under some circumstances, for example, when there is close contact between an infected person and an unprotected caregiver. However, limited transmission under such restricted circumstances does not indicate that the virus has gained the level of transmissibility among humans necessary to cause a pandemic.
Phase 4 is characterized by verified human-to-human transmission of an animal or human-animal influenza reassortant virus able to cause “community-level outbreaks.” The ability to cause sustained disease outbreaks in a community marks a significant upwards shift in the risk for a pandemic. Any country that suspects or has verified such an event should urgently consult with WHO so that the situation can be jointly assessed and a decision made by the affected country if implementation of a rapid pandemic containment operation is warranted. Phase 4 indicates a significant increase in risk of a pandemic but does not necessarily mean that a pandemic is a forgone conclusion.
Phase 5 is characterized by human-to-human spread of the virus into at least two countries in one WHO region. While most countries will not be affected at this stage, the declaration of Phase 5 is a strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short.
Phase 6, the pandemic phase, is characterized by community level outbreaks in at least one other country in a different.The current WHO phase of pandemic alert is 6.
During the post-peak period, pandemic disease levels in most countries with adequate surveillance will have dropped below peak observed levels. The post-peak period signifies that pandemic activity appears to be decreasing; however, it is uncertain if additional waves will occur and countries will need to be prepared for a second wave.
Previous pandemics have been characterized by waves of activity spread over months. Once the level of disease activity drops, a critical communications task will be to balance this information with the possibility of another wave. Pandemic waves can be separated by months and an immediate “at-ease” signal may be premature.
In the post-pandemic period, influenza disease activity will have returned to levels normally seen for seasonal influenza. It is expected that the pandemic virus will behave as a seasonal influenza A virus. At this stage, it is important to maintain surveillance and update pandemic preparedness and response plans accordingly. An intensive phase of recovery and evaluation may be required.
Assessing the severity of an influenza pandemic
The major determinant of the severity of an influenza pandemic, as measured by the number of cases of severe illness and deaths it causes, is the inherent virulence of the virus. However, many other factors influence the overall severity of a pandemic’s impact.
Even a pandemic virus that initially causes mild symptoms in otherwise healthy people can be disruptive, especially under the conditions of today’s highly mobile and closely interdependent societies. Moreover, the same virus that causes mild illness in one country can result in much higher morbidity and mortality in another. In addition, the inherent virulence of the virus can change over time as the pandemic goes through subsequent waves of national and international spread.
Properties of the virus
An influenza pandemic is caused by a virus that is either entirely new or has not circulated recently and widely in the human population. This creates an almost universal vulnerability to infection. While not all people ever become infected during a pandemic, nearly all people are susceptible to infection.
The occurrence of large numbers of people falling ill at or around the same time is one reason why pandemics are socially and economically disruptive, with a potential to temporarily overburden health services.
The contagiousness of the virus also influences the severity of a pandemic’s impact, as it can increase the number of people falling ill and needing care within a short timeframe in a given geographical area. On the positive side, not all parts of the world, or all parts of a country, are affected at the same time.
The contagiousness of the virus will influence the speed of spread, both within countries and internationally. This, too, can influence severity, as very rapid spread can undermine the capacity of governments and health services to cope.
Pandemics usually have a concentrated adverse impact in specific age groups. Concentrated illnesses and deaths in a young, economically productive age group will be more disruptive to societies and economies than when the very young or very old are most severely affected, as seen during epidemics of seasonal influenza.
Population vulnerability
The overall vulnerability of the population can play a major role. For example, people with underlying chronic conditions, such as cardiovascular disease, hypertension, asthma, diabetes, rheumatoid arthritis, and several others, are more likely to experience severe or lethal infections. The prevalence of these conditions, combined with other factors such as nutritional status, can influence the severity of a pandemic in a significant way.
Subsequent waves of spread
The overall severity of a pandemic is further influenced by the tendency of pandemics to encircle the globe in at least two, sometimes three, waves. For many reasons, the severity of subsequent waves can differ dramatically in some or even most countries.
A distinctive feature of influenza viruses is that mutations occur frequently and unpredictably in the eight gene segments, and especially in the haemagglutinin gene. The emergence of an inherently more virulent virus during the course of a pandemic can never be ruled out.
Different patterns of spread can also influence the severity of subsequent waves. For example, if schoolchildren are mainly affected in the first wave, the elderly can bear the brunt of illness during the second wave, with higher mortality seen because of the greater vulnerability of elderly people.
During the previous century, the 1918 pandemic began mild and returned, within six months, in a much more lethal form. The pandemic that began in 1957 started mild, and returned in a somewhat more severe form, though significantly less devastating than seen in 1918. The 1968 pandemic began relatively mild, with sporadic cases prior to the first wave, and remained mild in its second wave in most, but not all, countries.
Capacity to respond
Finally, the quality of health services influences the impact of any pandemic. The same virus that causes only mild symptoms in countries with strong health systems can be devastating in other countries where health systems are weak, supplies of medicines, including antibiotics, are limited or frequently interrupted, and hospitals are crowded, poorly equipped, and under-staffed.
Assessment of the current situation
To date, the following observations can be made, specifically about the H1N1 virus, and more generally about the vulnerability of the world population. Observations specific to H1N1 are preliminary, based on limited data in only a few countries.
The H1N1 virus strain causing the current outbreaks is a new virus that has not been seen previously in either humans or animals. Although firm conclusions cannot be reached at present, scientists anticipate that pre-existing immunity to the virus will be low or non-existent, or largely confined to older population groups.
H1N1 appears to be more contagious than seasonal influenza. The secondary attack rate of seasonal influenza ranges from 5% to 15%. Current estimates of the secondary attack rate of H1N1 range from 22% to 33%.
With the exception of the outbreak in Mexico, which is still not fully understood, the H1N1 virus tends to cause very mild illness in otherwise healthy people. Outside Mexico, nearly all cases of illness, and all deaths, have been detected in people with underlying chronic conditions.
In the two largest and best documented outbreaks to date, in Mexico and the United States of America, a younger age group has been affected than seen during seasonal epidemics of influenza. Though cases have been confirmed in all age groups, from infants to the elderly, the youth of patients with severe or lethal infections is a striking feature of these early outbreaks.
In terms of population vulnerability, the tendency of the H1N1 virus to cause more severe and lethal infections in people with underlying conditions is of particular concern.
For several reasons, the prevalence of chronic diseases has risen dramatically since 1968, when the last pandemic of the previous century occurred. The geographical distribution of these diseases, once considered the close companions of affluent societies, has likewise shifted dramatically. Today, WHO estimates that 85% of the burden of chronic diseases is now concentrated in low- and middle-income countries. In these countries, chronic diseases show an earlier average age of onset than seen in more affluent parts of the world.
In these early days of the outbreaks, some scientists speculate that the full clinical spectrum of disease caused by H1N1 will not become apparent until the virus is more widespread. This, too, could alter the current disease picture, which is overwhelmingly mild outside Mexico.
Apart from the intrinsic mutability of influenza viruses, other factors could alter the severity of current disease patterns, though in completely unknowable ways, if the virus continues to spread.
Scientists are concerned about possible changes that could take place as the virus spreads to the southern hemisphere and encounters currently circulating human viruses as the normal influenza season in that hemisphere begins.
The fact that the H5N1 avian influenza virus is firmly established in poultry in some parts of the world is another cause for concern. No one can predict how the H5N1 virus will behave under the pressure of a pandemic. At present, H5N1 is an animal virus that does not spread easily to humans and only very rarely transmits directly from one person to another.
Joint FAO/WHO/OIE Statement on influenza A(H1N1) and the safety of pork
In the ongoing spread of influenza A(H1N1), concerns about the possibility of this virus being found in pigs and the safety of pork and pork products have been raised.
Influenza viruses are not known to be transmissible to people through eating processed pork or other food products derived from pigs.
Heat treatments commonly used in cooking meat (e.g. 70°C/160°F core temperature) will readily inactivate any viruses potentially present in raw meat products.
Pork and pork products, handled in accordance with good hygienic practices recommended by the WHO , Codex Alimentarius Commission and the OIE, will not be a source of infection
Authorities and consumers should ensure that meat from sick pigs or pigs found dead are not processed or used for human consumption under any circumstances.
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