Health officials said on Thursday that it looks like the novel H1N1 swine flu virus will continue to spread in the US through the summer months, and then resurge in the autumn. This is different to the previous expectation that the swine flu virus would follow a seasonal flu pattern: abate in the northern hemisphere as it approached the summer, spend a few months in southern hemisphere countries that are now approaching winter, and then return to the northern hemisphere in the fall.
Two senior officials from the US Centers for Disease Control and Prevention in Atlanta held a telebriefing with journalists yesterday and spoke about the pattern of swine flu transmission in the US and also about infections among health workers and the need for more rigour in H1N1 infection control in health care settings.
Dr Daniel Jernigan, Deputy Director of the Influenza Division at the CDC said 89 per cent of flu cases the CDC are seeing now are the novel H1N1 strain, but the pattern varies widely across the US.
The latest figures from the CDC show that the number of lab-confirmed novel H1N1 cases in the US now exceeds 17,800, including about 1,600 that have been hospitalized and 44 deaths, but Jernigan said surveys suggest the actual number of novel H1N1 infections is probably much greater, and around 7 per cent of the population is currently reporting flu-like symptoms.
Although the overall proportion of outpatients being treated for flu-like illness is now below the national baseline (more or less as expected with seasonal flu), 17 states were still reporting flu activity, with patterns of infection vary significantly from region to region: Northeastern states continue to have the highest number of cases, especially New York and Massachusetts.
"The US will likely continue to see influenza activity through the summer, and at this point we're anticipating that we will see the novel H1N1 continue with activity probably all the way into our flu season in the fall and winter," said Jernigan.
He said he and his colleagues at the CDC expect the activity through the summer will be low and then "pick up later".
The virus continues to affect mostly younger people and so far it is not causing the level of illness and deaths among the elderly that would be expected with seasonal flu, although the symptoms are very similar: fever, cough, shortness of breath, chills and fatigue, and occasionally vomiting and diarrhea.
Jernigan stressed the importance of remaining alert to symptoms of flu, and especially if they arise in people with underlying conditions such as heart disease, asthma or diabetes. You should go to your doctor straight away if you have any underlying conditions and start to feel symptoms of flu, he said.
From the evidence so far, the CDC said the antivirals still work, the inhibitors particularly. The agency currently recommends them for use with high-risk patients that are already sick, those who are hospitalized, and anyone severely affected by novel H1N1.
As the summer months approach, and with the virus not abating, outbreaks are now occurring in summer camps. Although adults, teenagers and children at camps are catching swine flu, it appears that mostly children are affected in the summer camps and parents are advised not to send their children to summer camp until seven days after the onset of any illness or four days after it stops, said Jernigan, adding that:
"It's important also that aspirin is not used in children with influenza-like illness because of complications that can occur."
H1N1 Among Health Care Workers
In their 18 June issue of MMWR (Morbidity and Mortality Weekly Report), the CDC gives their latest assessment of H1N1 among health care workers.
The CDC figures, which include cases up to around mid-May, show that at least 48 health care workers have been identified with H1N1. From details of 26 of the infected workers, they found that half were exposed to H1N1 outside of their workplace, but the other half caught it at their workplace. At least one health care worker caught it from another worker, and the other 12 most probably caught it from sick patients, said the CDC.
Those who caught the virus from sick patients did not "consistently use all recommended forms of personal protective equipment while caring for these patients," said the CDC, adding that they did not fully follow the CDC guidelines for infection control in caring for patients with novel H1N1 in health care settings.
The CDC stressed that health care providers need to stick to the recommended infection control procedures, and especially recognize and triage potentially infectious patients and train staff to follow recommended practice and use protective equipment.
Dr Michael Bell, the Associate Director for Infection Control at the CDC said at the telebriefing that:
"Probably the single most important thing is that infectious patients be identified at the front door."
He said the "consistent application of precautions is important to make sure that there isn't occupational exposure," and identifying potentially infected patients "up front" is essential, whether they are "coming in through the emergency department or the ambulatory care clinic".
Bell said the CDC recommends using a single patient room for individuals that are infected and make sure they cover their cough.
Health workers should use respirators, gloves and eye protection when seeing to a patient suspected of having H1N1, and take extra care with hand hygiene, he stressed.
-- CDC: MMWR 18 June 2009.