If you are a health official facing two highly contagious diseases — one that is already killing dozens of people, and another that threatens to kill people by the thousands or millions, but hasn't yet done so — how do you allocate your resources? The answer can be a difficult balancing act, as the situation in China is showing.

At the moment, China's top health priority is the potential threat of pandemic H1N1 swine flu virus. Over the past weeks China has had 108 confirmed cases of H1N1, so far without any deaths. But officials fear that there could be enormous numbers of fatalities in the coming months if the virus spreads though the country's 1.3 billion people. Responding to World Health Organization (WHO) warnings and global concerns, China has acted decisively and sometimes excessively, possibly reflecting the country's delayed response to severe acute respiratory syndrome in 2003. Medical teams have been sent on to planes to measure the temperature of every passenger aboard, despite evidence saying that such measures are not particularly effective, and Mexicans have been quarantined seemingly just because they come from the country where the H1N1 outbreak was first detected.

At the same time, however, children around the country are falling ill because of hand, foot and mouth disease (HFMD) — an illness that has become an increasingly serious problem in may parts of Asia since a 1997 outbreak in Malaysia killed 29 people. Especially worrying is that, unlike diseases such as dengue fever or malaria, but like H1N1, HFMD can be transmitted directly from human to human; no animal reservoir is required. Cases start out with flu-like symptoms that can develop into characteristic sores in the mouth and rashes on the palms and soles of the feet. Infections can also lead to meningitis and swelling of the brain, possibly resulting in long-term neurological damage (L.-Y. Chang et al. N. Engl. J. Med. 356, 1226–1234; 2007) or even death. The vast majority of reported cases and almost all of the serious cases are in patients under 5 years old.

In 2008, more than 500,000 HFMD infections were reported in China, and 200 people died. This year, as the disease moves through its peak season, similar numbers look possible. There is currently no vaccine to prevent it and no drug to cure it. The best safeguard is good hygiene: HFMD transmission is mainly via saliva and faeces. But even Singapore, renowned for its cleanliness, has had 8,896 cases this year, and had had even more by this time last year. There have also been cases this year in Taiwan, Hong Kong and South Korea.

Most of the serious HFMD cases seem to be caused by enterovirus 71 (EV71), first isolated in California in 1969. EV71, in turn, is related to poliovirus — a fact that has some experts concerned. EV71's recent pattern, with a few isolated outbreaks that are building in frequency, is similar to that seen before the twentieth-century polio epidemics that killed or crippled tens of millions of people around the world (J. F. Modlin N. Engl. J. Med. 356, 1204–1205; 2007). Although it is far from certain that EV71 will follow a similar course, the virus does seem to have become increasingly virulent in China since 2004, possibly because of genetic changes (see Nature 458, 554–555; 2009).

Thus the balancing act: China, the WHO and all of the other health organizations are to be commended for mounting a vigorous response to H1N1 (see page 756). But given the ongoing damage being caused by EV71, and its potential for large-scale, person-to-person spread, they should also be mounting a substantial effort to understand and counter that virus. And indeed, the WHO had a meeting on EV71 in Beijing earlier this year.

Yet that good start is not enough. WHO representatives play down the importance of EV71, and there is little information about the virus on the WHO website. One EV71 specialist laments: “All resources seem to be going to influenza.” And in the meantime, many doctors in China still misdiagnose HFMD, partly because the virus and its symptoms change, and partly because there are still no good tests to identify it. More leadership, more education, more awareness and much more research on drugs and a vaccine are essential.