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Swine flu: you ask the questions

By Channel 4 News

Updated on 15 July 2009

Our experts answer viewers questions about the swine flu outbreak.

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Click on the topic links to go to related questions:
- The virus
- Catching swine flu
- Symptoms
- Protecting yourself
- Treatment and vaccines
- Children
- Other
The answers provided are of a general nature. If you have a specific concern, you are advised to contact your doctor or the official government swine flu helpline on 0800 1 513 513.

THE VIRUS

- What's the common factor that links the deaths?
Professor Robert Dingwall, University of Nottingham: There is no obvious common factor at the moment - and too few deaths to be able to work on looking for one.

- Are we still headed for 100,000 cases a day in August?
Robert Dingwall: There is no reason to dispute this projection.

-Is there an official estimate of the expected number of deaths?
Andrew J Easton, Deparment of Biological Sciences, University of Warwick: The estimates can only be expressed in terms of the possible range that MAY occur.

This is because it is necessary to extrapolate from the current knowledge and inevitably there is a degree of uncertainty in doing that. As the number of cases increases the degree of uncertainty reduces. It is important to appreciate that what this means is that the figure at the bottom of the predicted range is equally as likely as the figure at the top of the range, though the latter generally gets more attention.
Dr John McConnell, Editor of the Lancet Infectious Diseases: Official estimates for the UK range between 3100 and 65000. The lower end being equivalent do deaths in a winter of mild seasonal flu, and the upper end being equivalent to two or three severe winters of seasonal flu.

- How do we know that there isn't more than one infection sweeping the country?
Dr John McConnell: Because samples from a selection of people with the illness are tested for the presence of virus. In the early days of the outbreak, there was evidence of co-circulation of seasonal flu viruses, but these have been replaced by the H1N1 virus.

- Can swine flu spread to, or via, animals
Dr Steven McOrist, Nottingham University: Global scientific groups have now reported a wide range of specific animal and laboratory tests on the novel human H1N1 influenza virus that originated in people in Mexico and California in March 2009.

These tests include the effect of the new virus on the lungs and other tissues of test animals, such as ferrets, as well as transmission studies where healthy animals are placed in rooms, next to rooms containing droplets of the virus.

The results of these studies show that the new virus is similar to the current range of seasonal flu viruses in many ways, including the location and severity of changes it produces in the windpipe and lungs of test animals and its ability to spread to new animals in aerosols. It lacks key components and activity of the 1918 Spanish flu pandemic virus.

The new virus can easily be transmitted to pigs, which remain fully susceptible to this new strain. The H1N1 vaccines previously used in pigs in America do not appear to protect them from the new virus. The closest previous strain found to the new Mexico strain has been identified in Hong Kong from 2004, suggesting that global travel by people has been the vital contribution to the final make-up of the new strain.

- Why are the numbers for predicted infection rates so high over the next four years given we think most people will be vaccinated by early or middle of next year?
Dr John McConnell: Actually, most people won't be vaccinated. Only the minority of people who live in high-income countries are likely to be vaccinated within the next year. The poor majority will just have to suffer.

- What will happen in the next 3 - 5 years? Will the virus dwindle as immunities are improved or is it here to stay?
Dr John McConnell: An end point will be reached once transmission of the virus is interrupted because a sufficient proportion of the population is immune to infection. Immunity may be acquired naturally or by vaccination. This endpoint might be reached within less than a year in the UK once vaccine is available, but might take 2-3 years in countries too poor to afford vaccine. As with most infections, the world's poorest people will suffer the greatest burden of sickness and death. Andrew J Easton: The pattern that has been seen with all previous flu pandemics is that the virus infects a very large number of people in the first year or so - these individuals become immune to that specific virus.

In subsequent years the virus appears as a seasonal flu, infecting individuals who have not become immune. At the same time the virus mutates very gradually to become sufficiently different and then can infect some of the previously immune individuals.

In the coming months a very large proportion of people in the world will become infected (and will become immune). The virus will then mutate in the way that all flu viruses do and will be able to spread in communities.

Return to questions index

CATCHING SWINE FLU

- Is kissing the biggest spread?
Robert Dingwall: Unfortunately not. Actually, there is still a lot of debate about exactly how flu is transmitted and the relative contribution of droplets from sneezing (or kissing) and touching surfaces that have acquired droplets - from being sneezed on - with the virus being carried to the mouth or nose by the hands.

Professor Sally Bloomfield, London School of Hygiene and Tropical Medicine: The answer is that we do not know - it may be that shaking hands with someone could be even more risky.

There are 3 possible routes of transmission:
Droplet transmission: occurs when the infected individual directly sprays large droplets (droplets of size > 5µm) of infected mucous by coughing or sneezing, which propels the droplets onto conjunctiva of the eye (the virus enters the tear fluid and drains down a duct into the nose) or the lining of the nose of a susceptible host, where the virus then infects the mucous membranes.

Airborne transmission involves droplet nuclei (droplets of size < 5µm) and does not require face-to-face contact with the infected individual. Droplet nuclei settle from the air slowly and are respirable i.e. the virus can be drawn down directly into the alveolar region of the lungs where they infect the tissue of the lungs.


"What advice can you give to those with children and newborns?" Find the answer here.


Contact transmission involves hands and surfaces. Infected droplets of mucous are deposited on surfaces either by settling of airborne droplets or being touched with contaminated fingers.

An individual can pick up the virus if they touch a contaminated surface or shake hands with an infected individual with contaminated hands. They can then become infected if they rub their eyes or nose with contaminated hands when the virus infects the nasal mucosa.

It is thought that flu is transmitted by all 3 pathways, but there is disagreement as to the relative importance of each pathway. Whereas some experts think that droplet transmission is the major pathway for spread of flu and airborne transmission is of minor importance, others maintain that the role of droplet transmission has been overrated and that airborne transmission is a potentially important transmission pathway in indoor environments.

Flu can also be spread via the hands by contact with objects that an infected person has contaminated with infectious nose and throat secretions, although for flu there is less supporting evidence for this mode of spread than for colds.

Because large droplets settle out quite quickly, to get infected by kissing we probably need to get close to an infected person whilst they are coughing, sneezing and nose blowing. So passionate kising of someone who may be in the early stages of infection could be risky - as is being in close proximity at all to someone who is constantly sneezing and nose blowing, but it is unlikely that kissing is "the biggest risk" - and a kiss on the cheek is unlikely to spread the virus.

The most important rule is for people who are infected to act responsibly and keep away from crowded unventilated spaces and practice good respiratory hygiene.

- Is it better to catch swine flu in summer than winter? Should we seek out people with it to catch it now?
Andrew J Easton: There is no reason to assume that the virus will cause more severe disease in winter. It is not advisable to seek out infection since all infections carry a risk - you should not expose yourself to such a risk needlessly.

- When are people contagious? Is it only when symptomatic, or beforehand? Does it effect children differently?
Robert Dingwall: Mainly just before the symptoms appear and in the early symptomatic stages.  Children seem to shed more of the virus but over the same sort of timing.

- How long are you infectious for after symptoms disappear?
Robert Dingwall: You would normally have ceased to be infectious before the symptoms disappear.

John McConnell: People may be contagious from 1 day before they develop symptoms to up to seven days after becoming sick. Young children may be contagious for longer.

- After having swine flu when should a person go back to work? Do they need to stop having mild flu symptoms?
Dr John McConnell: If you're feverish you are almost certainly still fighting the infection. To be on the safe side, probably best to wait until seven days after the first appearance of symptoms before returning to work.

Andrew J Easton: Infected individuals should not return to work until the primary symptoms of fever have stopped. Generally a cough should also reduce or disappear at the same time - generally if it persists it is best to seek advice from a GP.

Have you got swine flu symptoms?

If you think you have swine flu stay at home and call your GP.

If the doctor confirms the virus by telephone they will give you a voucher reference entitling you to anti-viral medication. You then need a healthy friend to pick up the anti-virals for you from a collection centre using the reference number.

- Can you get swine flu twice?
Robert Dingwall: Theoretically - but unlikely.  Your body should have developed an immune response to the first attack that immediately deals with later exposures.

John McConnell: Highly unlikely, but not impossible if the virus mutates during the course of the pandemic.

- If my partner has swine flu, should I still go to work?
Andrew J Easton: Yes, as long as you do not have any symptoms of disease.

Return to questions index

SYMPTOMS

- If you feel generally unwell, with flu-like symptoms, at what stage do you then assume it might be swine flu - and why? What are the symptoms that stand out from normal flu?
John McConnell: A combination of fever plus flu-like illness (ie, two or more of: cough; sore throat; runny nose; limb or joint pain; headache; vomiting or diarrhoea) is now considered to represent a diagnosis of swine flu. There's no difference in signs and symptoms from seasonal flu, but because there's little current evidence of circulation of seasonal flu viruses it's most likely to be swine flu.

- Do you have to have all the listed symptoms to get a diagnosis of swine flu or just a few as there are quite a lot of symptoms?
John McConnell: See answer to the question above.

- Is it possible to have swine flu in the absence of fever?
Dr John McConnell: Yes, it probably is possible to have an infection so mild that you're hardly aware of it. But we can't be absolutely certain because people with very mild illness are unlikely to be tested for infection.

Return to questions index

PROTECTING YOURSELF

- If I contract the virus while I am pregnant are there any extra risks involved to me and or my unborn child with the virus or tamiflu?
Andrew J Easton: Any infection during pregnancy represents a risk to the mother and/or child. With flu the risk is extremely small and would not be expected to be threatening unless other underlying medical factors were present. There is no evidence that this strain of flu presents a higher risk than the seasonal flu with which we are familiar.

While there is no evidence that Tamiflu can cause problems to an unborn child pregnant women should seek medical advice before taking it in case there are other factors which have to be taken into account.

Dr John McConnell: Best follow the advice of the Chief Medical Officer on infection during pregnancy by clicking here.

- Can having the yearly flu vaccination and the pneumonia vaccination protect me from the swine flu virus, or go some way to help?
Dr John McConnell: Exposure to earlier varieties of the H1N1 virus, whether natural exposure or in the seasonal flu vaccine, might provide a degree of protection for some people, but not enough to affect the course of the pandemic.

Infection with the swine flu virus can lead to secondary infection with pneumococcal bacteria in rare severe cases of illness. The pneumonia vaccine will give protection against this happening.

- I work in a busy shop so does that mean I am more susceptible and what can I do to protect myself?
Robert Dingwall: You may be exposed to more chances to be infected just because you meet more people than most - but many people will be exposed through commuter journeys on buses, underground trains and so on so it probably doesn't add to your overall risk in the course of a day compared with, say, someone nursing a ward full of swine flu patients. You don't need to do anything special to protect yourself beyond the personal hygiene measures, like regular handwashing.

Professor Sally Bloomfield, London School of Hygiene and Tropical Medicine: The fact that you work in a closed environment, where different people are coming in and out all the time, does increase the risk. Some things you can do to reduce the risks are to keep the shop well ventilated (i.e doors and windows open), wash your hands frequently, or if this is not possible use an alcohol hand gel. Try not to rub your eyes and the inside of your nose (not easy!) with your hands - use a tissue if necessary.

Also regularly clean and disinfect (using a bleach) all "communal" hand contact surfaces such as door handles. If any of your colleagues start to become unwell - send them home immediately.

- Once you have had swine flu, whether mild or severe, are you then immune to it? If you are immune would you still be immune if it mutates?
Andrew J Easton: After infection you will be immune to re-infection with that virus. If the virus mutates in a way that allows it to avoid the aspects of the immune system that provide immunity you would then be susceptible to a second infection.

That is the basis for people being infected with seasonal flu in successive years - the virus has altered sufficiently in the intervening period to be able to avoid the immunity that had been established.


"How effective is tamiflu and can it be taken twice?" Find the answer here.

- How long does the swine flu virus survive on hard or soft surfaces and how effective is the use of hand gel when trying to avoid infection?
Sally Bloomfield: From what we know about influenza viruses they are shed in large numbers from an infected person (Up to 10 million influenza particles per ml in nasal secretions). Survival times for aerosolized particles vary between one and 24 h. The virus can also survive on surfaces such as stainless steel and plastic for 24-48 hours, and for up to 12 hours on soft surfaces such as cloth, paper and tissues. Thankfully, the virus survives only short periods of time on the hands; investigations suggest that, after transfer to hands from surfaces, viable virus falls to a low level within five min.

If, however, virus on surfaces is being constantly renewed and there is frequent hand contact with these surfaces, then even short survival times on human skin make transmission from the hands to the lining of the nose or the conjunctiova of the eyes (which is how the virus infects) probable. Data suggest that if people are not being watched, nose-picking and eye-rubbing occur at a rate of approximately 0.4 h-1, although if people are facing each other the rate is 10 times less. Because the  virus survives quite well on surfaces such as door handles, light switches or telephone buttons this increases the possibility of hand transmission in highly frequented public settings such as hotel rooms, public transport, public toilets etc. Washing hands thoroughly under running water will remove the virus, but if you do not have access to a sink, use an alcohol hand gel. This should destroy any flu virus on the hands within 30 secs to 1 min.

Return to questions index

TREATMENT AND VACCINES

- How effective is tamiflu and how long do the effects last?
Robert Dingwall: Tamiflu can only reduce the severity of symptoms and shorten the duration of illness. It does not work like an antibiotic that attacks the infectious agent directly. Tamiflu prevents the virus from multiplying in your body so that your own immune system can deal with it more quickly and effectively. Once you have had flu, you will have a degree of immunity that means you are unlikely to be infected again by this particular strain. There are some suggestions that if you have Tamiflu very soon after exposure to infection, you may develop immunity without ever experiencing symptoms - but the evidence on this does not yet seem to be conclusive.

Swine flu symptoms

A combination of fever plus flu-like symptoms i.e coughing, sore throat, runny nose, limb or joint pain, headache, vomiting and diarrhoea.

- Can you take tamiflu twice? My two year old son will be given tamiflu as soon as anyone close to him shows swine flu symptoms. This may mean he ends up taking tamiflu without actually having swine flu.
Robert Dingwall: What you may find is that exposure plus tamiflu triggers an immune response anyway - there is some positive but inconclusive evidence that this can happen.  If not, further doses of tamiflu are not known to cause problems and will be as effective. 

John McConnell: Yes

- When will the vaccine be available to young children such as the under-5s?
Robert Dingwall: The vaccine may not be tested for, or suited to, very young children in the first instance. However, they will gain immediate benefit from other people being vaccinated, which will reduce their exposure to possible sources of infection. It's a bit like MMR - vaccinating toddlers protects babies who are too young to be vaccinated as long as you vaccinate enough of them to prevent measles being transmitted from one unvaccinated child to another.

John McConnell: It's looking increasingly likely that a vaccine won't be available until the end of this year.

- If everyone is vaccinated, doesn’t this pose a greater threat to finding natural immunity?
Robert Dingwall: No. Vaccination works by provoking the body to produce an immune response, which it then remembers. In effect vaccination is an artificial way to create natural immunity.

John McConnell: This is one of those empty myths that needs firmly debunking. Your body will mount an immune response to antigens that it recognises as "non-self"; it doesn't care whether the antigens are the "natural" wild virus or a man-made antiviral vaccine. However, because the virus is capable of reproduction it is also capable of making you ill; whereas because the vaccine is just viral proteins it will generate only immunity and not illness.

- Are there going to be any vaccines available NOT grown on egg albumen for people with allergies?
Prof Peter Dunnill, University College London: To my knowledge, a modest amount of vaccine grown on a cell culture (rather than egg albumen) has been ordered.

Return to questions index


"What is the advice for pregnant women?" Find the answer here.

CHILDREN

- What advice can you give to those with newborns?
Robert Dingwall: Careful personal hygiene - wash your hands regularly and clean surfaces touched by the baby. It may be a good idea to avoid very crowded public spaces like commuter trains - but would you take a baby on one anyway? Ask friends and family not to visit if they are not entirely sure they are well and minimize close contact like kissing the baby or holding it.

- I have a 3-year-old daughter - Is the advice for children that if they've got a temperature and a sore throat, they should have anti-viral drugs as a precaution?
John McConnell: Diagnosis in children is made on the same basis as adults. Children should be offered Tamiflu.

Do children with asthma have severe complications if they get swine flu?
Dr John McConnell: Asthma may make the illness produced by the swine flu virus more severe. See official guidance here.

Andrew J Easton: People with asthma have a higher probability of experiencing severe symptoms of disease when infected with any respiratory virus. This is also true for the new strain of flu.

- The NHS website says that the under 5s are "particularly susceptible" and an "at risk" group. In what way is this true?
John McConnell: Not fully understood, but likely to be a combination of factors including immature immune systems in under 5s, patterns of mixing among children, and their poorer understanding and execution of hygiene precautions.

- I've got a one month old child. If I catch swine flu - even very mildly - is he likely to get a more serious form because his immune system is less developed?
John McConnell: Your child won't necessarily catch swine flu even if you have it. Very young children are known to be at higher risk of severe illness with season flu, so the same is likely to be true with swine flu. However, the risk of death in young children is very small. Young children can be treated with Tamiflu, and you should see your GP if your child becomes ill.

Return to questions index

OTHER

- I'm travelling to USA on holiday in 10 days time - if I develop cold or flu like symptoms before travelling will I be allowed to board a plane?
John McConnell: According to the guidance given by the US Centers for Disease Control: "If a cabin or flight deck crew member or passenger is displaying signs and symptoms of an ILI [influenza-like illness] prior to flight, they should not board the aircraft" (see http://www.cdc.gov/h1n1flu/guidance/air-crew-dom-intl.htm)

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