The number of people with symptoms of swine flu has fallen dramatically in the past week with growing signs that the recent outbreak may have peaked ahead of an expected second wave of infections later this year.
Official figures released yesterday show that the weekly consultation rate between doctors and patients suffering from flu-like infections has fallen almost to normal levels but government scientists warned that this is likely to be a temporary lull before a second outbreak occurs after schools re-open in September.
The Health Protection Agency estimated that there were about 30,000 new cases of swineflu last week compared with more than 100,000 cases a week at the peak of the summer outbreak. However, it emphasised that there are large uncertainties in the estimates, with the true figure for last week lying anywhere between 15,000 and 85,000 new cases.
Last week also saw a sharp decline in the number of people with swineful symptoms seeking consultations with GPs, with the weekly average running at 42 consultations per 100,000 people, just above the normal "baseline" of 30 consultations per 100,000.
The decline in consultation rates occurred in all age groups and in all NHS primary care trusts in all regions of the country. No primary care trust reported an increase in the weekly rate of people seeing their GPs because of flu-like symptoms.
The total number of people with swineful who have died in England rose from 27 to 36 but Sir Liam Donaldson, the Government's Chief Medical Officer, said that not all of the extra deaths occurred last week because of delays in reporting the figures and that nothing significant could be read into the extra nine reported deaths.
"All the trends are indicating a further downward movement" in the number of people infected with the H1N1 swineflu virus and there are no signs that the virus is evolving into a more severe disease or becoming resistant to the anti-viral drugs being distributed to combat the infection, Sir Liam said.
However, experts believe that a second wave of infections is highly likely later in the year, probably after children return to school at the end of the summer holidays, when the virus will have the opportunity to spread further. "We are pretty certain a second wave will come, but we're not clear when this will be," Sir Liam said.
The Government will continue to plan for a mass vaccination campaign when a vaccine become available, despite signs that the infection is relatively mild in the vast majority of people who get infected. "If you abandon this [mass vaccination] then you take the view that it's acceptable that a substantial number of people will die," Sir Liam said.
Scientists at the Health Protection Agency's Respiratory Virus Unit in Collindale, north London, have now analysed 607 samples of H1N1 virus for signs of drug resistance and none were found to be positive. A further 110 specimens were all found to be susceptible to Tamiflu and Relenza, the two anti-virals stockpiled by the Government.
Meanwhile, there are signs that the virus is spreading in the southern hemisphere, at the height of its winter flu season. Deaths have almost doubled in Argentina and they have also risen sharply again in Mexico, which may be entering a second wave of the epidemic - the first country to do so.
Sir Liam said that the Government is also closely monitoring the situation in Australia where there has been more than 24,000 confirmed cases of swineful and nearly 80 deaths, with 422 people with swineflu currently hospitalised and 117 of them in intensive care.
In Britain there has been a fall in hospitalisations in all age groups suffering from swineflu, with the biggest decline occurring in children under the age of five. There has also been a decline in the number of people seeking medical advice from the National Pandemic Flu Service, a helpline designed to give guidance on whether people need to take anti-viral drugs.
Sir Liam said that there are no plans to disband the helpline even if the decline continues - although it may be scaled down - because it will almost certainly be required later in the year when the second wave is expected.